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Thursday, July 13, 2017

How are RV tires developed?

 By Roger Marble

If a tire is being designed for a specific vehicle manufacturer such as Ford, Chevy, Toyota, or BMW, there will be a number of tires submitted by competing tire companies all trying to deliver the best overall compromise in performance characteristics. Please note that all original equipment ("OE") vehicle manufacturers have slightly different requirements but all make similar requests for performance improvements in many areas. In the future I will use the term "OE" to include these car and pickup manufacturers.

Compromise: Now is a good time to talk about some of the various trade-offs the engineer is faced with when trying to meet conflicting goals and customer wants. I am sure we would all like an RV that has all the interior space and amenities of a 40’ diesel pusher but gets 25 mpg and can be driven down crowded city streets without knocking off our mirrors. Oh yes, it should also cost under $30k. Well, Bunkie, that just ain’t gonna happen in real life.

The same goes for a tire that handles like an Indy tire, is as quiet as the proverbial mouse, has great off-road traction, is good for 100k miles, and costs $25. One thing few people realize is that most if not all performance characteristics are a compromise. For example, if you improve wet traction you probably hurt fuel economy unless you use a special type of rubber that costs double per pound and is more difficult to process. If you improve handling you might hurt ride and noise. When you improve noise you can significantly increase the cost of making the molds used in manufacturing. The cost of a tire mold can be as low as $10,000 and can approach $100,000 each. Depending on the production volume needs, a tire manufacturer could need 30 or more molds. The list of trade-offs goes on and on.

The competition for a tire application might start three or more years before scheduled start of delivery with two to five tire manufacturers competing for the contract, knowing that only one or two will end up being selected to actually provide tires. The costs associated with building and testing special prototype tires can run in the hundreds of thousands of dollars and are absorbed by the tire company. The only way a tire company can afford this type of activity is by landing a contract for a few hundred thousand tires so the costs can be spread out.

Unlike “OE,” an RV manufacturer may only need a couple thousand tires, so a custom tire designed for a specific RV would be cost prohibitive. Since the RV manufacturer won’t be trying to get custom tires, it doesn’t have staff engineers working on developing specifications for such tires. The RV company will in all likelihood either take what comes already on the cut-away chassis or the bare chassis for Class-C or A vehicles, and in the case of trailers, may buy the tire with the lowest cost that can meet tire size requirements and expected delivery schedule.

For RV applications the one thing that is in the control of the manufacturer is “Reserve Load.” This is the difference between the load placed on each tire with the RV normally loaded and the load capability of the tires at specified inflation.

##RVT802

Tuesday, July 4, 2017

"Care and feeding" of your valve stems

I suggest that if you are looking for long "bent" metal stems you ONLY get them installed by a Truck Tire store. Preferably not just a "dealer," as anyone can sell tires, but a "company store" that is owned by a tire company or a store that is part of a large chain, as they are more likely to have a selection and actual training on proper installation of long truck valve stems. The shop should have the proper tool for bending the long brass stems without cracking them, if bending is needed.

With long stems it is also important to remember to not just press the air chuck or pressure gauge onto the end when adding air or checking pressure as you can generate a lot of force on the joint between valve and wheel. Always support the stem or hose extension with your other hand even if the stem or hose has a hard mounting, as you can loosen the mounting point too.

There are specifications for torque of the metal nut for bolt-in valve stems. (25 to 45 inch pounds) This is especially critical on your car or truck if it came from the factory with an internal Tire Pressure Monitoring System (TPMS). Many of the internal TPMS are made of aluminum for light weight and as such have very low torque specs. It is easy to break the aluminum nut or, even worse, the stem itself – which could cost you $50 to $100 to replace.

"Tire Review", a trade magazine for tire dealers, had an article on TPMS sensors and they point out the following:

"What is the torque value required for the nut?
Typical torque values for the base nuts on a TPMS valve stem range from as low as 35 in.-lbs. of torque to as much as 80 in.-lbs. of torque. That’s quite a range. This doesn’t mean that any torque value within this range is acceptable. It means that the torque specifications for the base nut on one vehicle might re­quire 44 in.-lbs., another might re­quire exactly 62 in.-lbs., yet another might specify exactly 71 in.-lbs., and so on. Don’t guess. Look up the torque specifications for the vehicle you’re servicing to make sure you use the correct torque.

Why should the nut be replaced every time a sensor is serviced?
The nut is made of a softer metal than the stem, so it will be damaged – not the sensor – if it’s over-tightened. The material of choice is typically aluminum. If the nut is over-tightened, it will develop hairline cracks."

NOTE: Those specs are INCH-Pound, not your normal Foot-Pounds. Here is a picture of my TPMS Inch-pound Torque Wrench.




Standard "metal bolt-in valves" also have specs for the nuts and those valves are usually brass or plated with nickle or chrome. I am not aware of any stainless steel valve stems for regular automotive use. There are some aluminum bolt-in stems too, but those are expensive lightweight units made for race car application which would not normally be sold without being identified as such.

Even valve core have a spec (2 to 5 in-lb) as there is a tiny gasket that can be distorted and even broken if you over-tighten the core. There are some special tools. But rather than buy some special tools I suggest you tighten core till air stops, add no more than 1/4 turn more, then confirm no air leak by testing with soapy water. When no bubble forms the core is tight enough. I then attach the metal valve cap to ensure no air is leaking. There have been a few cases of slow leak through the valve core that ended up as a tire failure as no metal cap was used. The cap is primarily intended to keep dirt out of the core area but is also a "backup" on preventing air lost past the core.

Whenever "messing" with your valve it's always a good idea to confirm there are no leaks with a quick spray of soapy water.

##RVT801


Tuesday, June 27, 2017

Change your own tire ?

For my Class-C  I have a bottle jack with a rating greater than GAWR of rear axle. Since I would only jack one side that gives me plenty of lifting power. It's also easier to jack while laying on the ground.😥

Harbor freight has good deals.
An important item is a large flat plate to support the jack if not on concrete.
Maybe 12" x 12" 1/4" thick steel plate or 2" wood but you might still need a 6"x6" 1/4 steel so you don't split the wood.  Check with local shop offering welding or tow hitch install as they many times have scrap pieces available.

If jacking, be sure to set brake and block the tires front & back so the RV can't roll.

Whenever I change an outer dual I run a couple lug nuts on the inner (hand tight is good enough) as soon as I remove the outer, just to keep one wheel under the coach in case something slips with the jack.
If changing the inner dual I temporarily use the outer tire as safety backup.

IF YOU RUN 19.5 or 22.5 tires
I strongly suggest you get a service truck and let them wrestle the 150#+ tire and wheel around.

Also it is important to remember if you have lost more than 20% of your air in any tire it is considered flat and if you drove any distance on it you may have damaged the body and it could explode when re-inflated.  Inform the tech and let them inspect and re-inflate or replace. This could result in injury or worse.



Subscribe to the weekly RVtravel.com newsletter or one of our other newsletters about RVing. Great information and advice. Now in our 16th year. Learn more or subscribe

##RVT800

Should you "plug" your tire?

This is an oldie but goody.  I was just asked about plugging tires.

 This is a very important post. Improper repair can lead to a false sense of security and even to a tire failure which can cause damage or even injury. Please read this entire post.

I recently read a statement that could be misleading as it is not supported by any of the major tire manufacturers or the National Highway Traffic Safety Administration.

The writer said that “plugging a tire can work well.” This is just as true as making a statement that you can play Russian roulette and survive or you can beat the odds in Vegas or you can survive jumping out of a plane without a parachute.

Guidelines for proper repair of a tire for highway use are available from a number of sources.

Your well-being may depend on following these guidelines from NHTSA.
“The proper repair of a punctured tire requires a plug for the hole and a patch for the area inside the tire that surrounds the puncture hole. Punctures through the tread can be repaired if they are not too large, but punctures to the sidewall should not be repaired. Tires must be removed from the rim to be properly inspected before being plugged and patched.”


If you don’t trust NHTSA, How about Goodyear?
“It is crucial to know when it is okay to have a tire repaired and when a tire should be replaced. If a tire loses its air pressure, it must be removed from the wheel for a complete internal inspection to be sure it is not damaged. Tires that are run even a short distance while flat are often damaged beyond repair.
Most punctures, nail holes, or cuts up to 1/4 inch can be repaired by trained technicians as long as the damage is confined to the tread. DO NOT repair any sidewall puncture. Most tire repairs should be handled by trained professionals.”

If you don’t like Goodyear, maybe Michelin?
“There is a good chance that your tire can be repaired if:
1. The tire has not been driven on when flat
2. The damage is only on the tread section of your tire
3. The puncture is less than ¼"
However, you need to have an authorized tire retailer or technician remove the tire from the wheel and inspect the tire from the inside. This inspection is absolutely necessary because internal damage is not visible while the tire is mounted.
The proper way to have a tire repaired is to patch the tire from the inside and fill the puncture hole. If someone offers you a plug repair, refuse! Plug repairs do not involve taking the tire off the wheel for a proper inspection. A plug is simply inserted into the punctured area. Plug repairs are not reliable and can lead to tire failure. Insist on a full inspection and patch and fill repair on the inside of the tire.“

OK, not Michelin, then maybe Bridgestone Firestone?

“Tread punctures or penetrations left unrepaired may cause irreversible tire damage. An improper repair can damage the tire and will void the warranty.
Combination patch/stem repair. Steel cord damage must be repaired immediately to prevent rusting of the steel. Using plugs or patches alone on any type of tire is not a safe repair.“

Here is an example of a tire with three plugs and the owner also used a sealant that goes through the valve, all in an effort to save a couple of bucks.


Here you can see the cracks through the interior rubber of the tire from driving hundreds of miles on an under-inflated tire.


This tire had a piece of wire sticking into the air chamber. You can see where it was wearing through the interior.

None of these “repaired” tires were dismounted as instructed by tire manufacturers but each had a cheap, improper plug repair made by someone that thought they knew something about tires. I will leave it up to you to judge the quality of the suggestion that a plug is acceptable repair and "can work well".

As you can tell this topic is a “Hot Button” for me as I have seen entirely too many improper repairs done by the uninformed in the name of saving a couple of bucks.

##RVT800

Monday, June 19, 2017

Another example of learning correct tire inflation

Quote:
Originally Posted by Ron View Post
Tireman9 and others....I just ran my coach over to the local Cat Scales at a truck stop nearby. As I stated earlier they do not make things easy and a 6" curb on each side of the scales prevented me from putting each side on separately so that I could get a close four corner figure. I settled on the two axle approach. All tanks were full, (water tank was actually just over 2/3, it fills very slowly and I got bored). Front axle came in at 11,400 lbs, rear axle was 16,560 lbs. My front axle is rated at 13,300 lbs and the rear is 21,000 lbs with a GVW of 34,300 lbs. 295-75R-22.5 tires. I have looked at the tables but would like to see what you folks come up with for approx. front/rear inflation? Thanks, Ron
Ron, you didn't say the brand tires. To my knowledge all major brands except Michelin have the same info for load & inflation and Michelin is same on maybe 95% and those that differ may only differ by 5 psi or so.

Since you only have total for an axle and do not know the heavy side we estimate one side at 53% -- So Front would be 6,042 and rear 8777 (4,389 per tire).

Most 295/75R22.5 LR-G need 110 to support 6,175 F (single) and 80 psi to support 4,540 in Dual.

Since I recommend a +10% of air for a good margin, that would suggest 121 psi front and 88 for the rear. BUT a LR-G is only rated for 110 psi so you need LR-H on the front. Also need to confirm the front wheels are rated for 120 psi and since even H are only rated for 120 that makes the recommended Front inflation 120 psi.

Clearly the estimate of 53% is causing the problem so it increases the need for you to learn the actual side to side load on the tires by going somewhere other than CAT truck stop scale.

It is CAT policy to not do one side weights and that is why they are making it harder to only get one side on the scale.

I suggest RVSEF

Check this site for scales

SmartWeigh is another option

I checked around home and found a local building supply that had a scale that would give me 4 weights for $10. Only about 3 mi off I76 just East of Akron OH.

##RVT799

Monday, June 12, 2017

"Dry Rot" is a misnomer regarding tires

Read this on an RV trailer forum, but most of the info applies to all types of tires.


"My understanding is that there seems to be a belief or a known orthodoxy that despite external appearances, the inside could rot out and that tires that appear all fine and dandy on the outside, after that long are not on the inside?

I believe the only "proof of concept" is common anecdotal experience:

People have owned tires that appear fine that are "old yet all seems fine", and they experience unanticipated tread separation and such....several anecdotes to the point of it being a "common wisdom" best I can tell.

Beyond that, I have not seen a "more objective" verification of this...in my mind, after the death of such an "old yet otherwise in good shape and used properly" tire, an autopsy of that tire could show evidence of this "rotting from the inside"....I am not sure anyone has posted details about what that would look like (beside unexplained otherwise tread separation)?

Absence of such "more objective review", I am very very inclined to accept the common wisdom or orthodoxy on this matter until clearly proven otherwise as the cost of being wrong is potentially massive comparatively!!!!!!!!! Many many posts on this site have expressed huge regret about pushing past such "widely accepted advice"

My response to the above:
I did "tire autopsies" for decades before retiring. I have even posted pictures on my blog and have over 30 posts that have "Failure" as a label. Best advice I can give is to read and review the information on my blog. Listen to the only two (to my knowledge) actual tire engineers on RV forums: myself and CapriRacer.

"Dry Rot" is a misnomer. Rubber is a long chain polymer. The chemistry is such that the polymeric chains break down over time. The rate the chains break is related to heat and other energy (UV) input. Nothing is actually "drying out" or "rotting" in the common understanding of the word. Sidewall cracking (dry rot) is just a symptom that suggests the internal rubber compounds have probably lost some of their elasticity, which increases the potential for cracking, which may lead to separation.

There is no single answer to why some people have longer tire life than others except for the fact that some operate their tires at higher temperatures (load, speed and inflation plus ambient temperature) than other people.

Any tire can fail with a Low Inflation sidewall flex failure or "Blowout". Radial tires in trailer application are exposed to significantly higher Interply Shear forces due to suspension design that the tires on the tow vehicle - See my post on Interply Shear.

While operating a tire can help the "Anti-Oxidants" or AO's migrate to the surface, simply driving the tire is not IMO an efficient or effective thing to do, especially when we consider that cleaning of the tire sidewall, which will remove the AO's, can result in more harm that any driving around can prevent.

How many of you have bothered to make load and inflation adjustments necessary for driving your ST type tires any faster than 65mph?

Do you even know the actual loads on your trailer tires?

How many do an annual "free spin" inspection of your trailer tires?

How many are running TPMS (tire pressure monitoring systems) so you get warned when you drop down to the minimum inflation needed to support the measured tire load?

If you feel that checking your pressure with a hand gauge is sufficient, do you make that check every 10 to 15 minutes of operation? If you have a tire leaking air you can destroy it in just a few miles, so the fact you checked the air 4 hours prior to the failure is of no importance.

Sorry for the rant but the FACTS are out there. It takes a little effort to drastically reduce the potential for premature tire failure. There is no magic snake oil spray that will make your tires last 20 years. There are steps that you can take to get 5+ years of life in trailer application and 7+ in motorhome and tow vehicle application.

##RVT798

Monday, June 5, 2017

"Only" drove 750 miles with companion dual tire low on air

Quote:
Originally Posted by Charlie View Post
What should I do? I had checked tire pressure the day before and only drove about 750 miles when the right rear inside duel blew resulting in damage to the MH and the tow. Only the side wall blew and the tire stayed on the rim. This is the first time in over 25 years of RVing that I have ever had tire trouble. I only had about 14,000 miles on these tires that are less than 2 years old. I bought the best tires they recommended. I will not say the brand but it begins with M.
I had pressure set at 120 psi and they were filled when the tires were cold and had not been driven for over a month, Should I be concerned about the other tires?


Should you be concerned? It depends. Why did the tire fail? If the failure was a sidewall flex failure (sometimes called a "zipper") from running low then there was most likely an active leak, i.e. puncture or leaking valve core would be on the top of my list. In this case the other tires are no more likely to fail next week than they were last week with one exception to be covered in a moment.

If you take the failed tire to a heavy truck tire dealer for the brand involved they should be able to confirm the mode of failure.

Since you were not running a TPMS (tire pressure monitoring system), all we know is that probably sometime between checking the tire pressure and 750 miles later (2 days?) one tire had lost most/all of its air. We also know that the outer dual was run with possibly 100% overload so it probably sustained internal structural damage that shortened its life (months or years). Since we do not know how many miles at what % overload, it is impossible to predict -- so the suggested best practice is to replace the companion dual.

One thing we can do is to use this as a learning experience. With a TPMS a driver would get early warning and many times can stop before a tire is damaged and, by extension, avoid damage to the RV and even not damage the mate in a set of duals. A single warning in the life of a TPMS (years) could save much more than the cost of the system.

Now as to the other possible reason for a tire to lose air. It is possible for a piece of grit to get into the valve core and allow air to leak. I suggest you review the posts on "Valves" (list to the left) and you can see an actual example of a leaking tire and the grit that caused it. So, as I have pointed out in the past, the very act of checking air pressure can sometimes result in a leak and potentially a failed tire.

##RVT797

Monday, May 29, 2017

Is your TPMS warning psi set correctly?


Originally Posted by Dan O. View Post
"The 'Safety Steer' is definitely a good bit of insurance. I also run the tire monitor system on all six MH tires and the four race trailer tires. I run 110 pounds in the coach tires and did pick up a nail in a steer tire one day. At 80 pounds the tire alarm went off (handling felt the same) and I saw 40 degrees more temperature in the low tire. Point is, some other warning signs are sometimes there before you experience an actual blowout."

I suggest you change the warning psi level. Many TPMS come with a single warning after a loss of 20% from the cold inflation. We all know that when running, tire inflation can increase 10 to 20 % from the CIP (cold inflation pressure). I would suggest that if your CIP is 110 then the warning should be no lower than 100.

Some TPMS provide early warning and alert when the hot pressure has dropped faster than normal so you can gain seconds to minutes advance warning if the TPMS provides "rapid air loss" warning or some other warning based on the hot pressure.

For example
Based on weight my small Class-C needs at least 65 to support the measured load. I use 75 as my CIP and my warning level is 65. My normal hot pressure is 80 to 85. If I pick up a nail I would get a warning if a tire looses more than 3 psi in a couple minutes so I might get a warning at 77 to 82 psi, which is well above the minimum needed by the tires for the actual load.

If a tire loses 20% of the air needed to carry the load it is officially "flat" for warranty purposes so there is a potential that the driving as Dan did with the tire down at 88 was damaging the tire structure which could shorten its life by months or years.

According to the U.S. Tire & Rim Association the warning signal from your TPMS should go off if inflation ever drops to below the level needed to support the actual load on any tire.

##RVT796

Monday, May 22, 2017

Goodyear Endurance ST tire info

I have been in touch with Goodyear and while there are still some technical details that need to be clarified, I have permission from GY to post the info sheet and the Load & inflation chart. (Click on each image for a much larger view.)







Monday, May 15, 2017

Another example of pressure and TPMS setting calculations

David said:

"I am a newbie. Just 5 weeks with my 2017 Newmar Bay Star 3113. I need some help understanding just what would be the correct or appropriate tire pressure on my coach. When loaded with my wife, dog and self, partial food and clothing, tools, chairs, BBQ ladders, 2/3 water, full gas and propane and misc stuff I got the following from the CAT scales: Front axle - 7,300. Rear axle - 13,260.

Here is my dilemma: The dealer delivered the coach with about 85 lbs. per wheel cold, but when I use the Michelin tire pressure chart for my 235/80R 22.5 XRE tires they should be just 75 lbs! I am concerned that they will be "underinflated" and could build up excess heat. Should I keep the 85 lbs. or lower the pressures
?"


My reply:
David, Welcome to RV fun.

For all things tires (except buying) I obviously suggest you check my blog. I don't expect folks to remember everything but if you spend a few minutes checking it out you will learn how to use the "Label List" on the left to find a post of the topic of interest. There is also a search box in upper left.  Now to your specific question.

1. We want to know the heaviest load on your tires and since few RVs are perfectly balanced side to side for weight we ideally want to know the "4 corner weight" to learn the heavier end for each axle. Lacking knowing that number, IMO, we can do a rough calculation by using 53% of the axle scale weight for the RV when it was fully loaded (the expected heaviest it will ever be).

2. 53% of your front would be 3,870# and rear would be 7,030# or 3,515 on each dual.

3. Looking at the Michelin load tables we find for your size at 85 psi can support 3,975 for single (front position) and 80 psi supports 7,050# for two tires in dual position.  Yes, we always round up.

4. Based on the above, your MINIMUM inflation would be 85/80. This is the number I would use for the low pressure warning numbers on your TPMS.

5. I recommend adding 10% and again, rounding up, that means 93/88 psi for your Cold Inflation Pressure or CIP. In your case, given the close numbers for the front load, I would be comfortable using 90 psi all around, as a single number is easier to remember. This 10% gives you a nice cushion so you do not have to chase your tire pressure around whenever the temperature rises or falls. You could even get down to 85 psi before needing to "top off" the tire pressure again.

6  All tires on an axle should be inflated to the same level for improved handling and response in an emergency situation.

7. I would set the TPMS High Pressure warning to 110 to 115 psi and your high temperature warning level to 160 F.

8 Remember CIP means when tires are at ambient temperature and have not been in direct sunlight or driven on for at least two hours.


Finally, in your case, you are close to some numbers when we round so if your RV is more balanced than my suggested 47/53% you may be able to lower my suggested inflations by 5 psi, but only when you confirm your heavier end is less than 53% of the total.

##RVT794

Monday, May 8, 2017

Why do some tires "explode"

OK, let's see if I can cover the details of why and how a tire sidewall fails due to being run without proper inflation.

The mechanics are essentially the same, be it a textile (usually Polyester) tire, as are most P, LT, and ST type tires, or for tires with steel body cord, as most commercial grade LT tires and "TBR" "Truck-Bus Radial" tires. These cords are referred to as the "body ply."

I think we all realize that tire sidewalls bend when loaded. This can be observed by simply looking at the bottom (near the road) vs. the rest of the tire sidewall. The amount of bending is essentially just a function of tire size, load and inflation. This bending includes some stretching of the outer surface of the tire and of the rubber surrounding the body ply. This stretching results in some heat being generated. You can test/experience this heat generation yourself with a simple test of holding a rubber band against your lip and stretching and releasing the rubber band. Your lip is sensitive enough to feel the temperature rise of the rubber band.

Now the rubber used in tire construction can tolerate some temperature rise. The heat generated can transfer to outside air at about the same rate it is being generated. This is what happens for hopefully tens of thousands of miles and hundreds of thousands of revolutions, i.e., sidewall flexes.

So what happens if there is a leak of inflation air, or if the tire was not properly inflated in the first place? With lower air pressure the amount of bending increases and with an increase in bending we see more heat being generated. Increased heat generation means increased temperature of the rubber internal to the tire structure. Since rubber is a good insulator, heat transfer can be slower than heat dissipation to the outside air, so the temperature can continue to rise ever faster.

The strength of the rubber decreases with an increase in temperature, which allows more bending. With slower heat transfer from the internal structure to the outer surface and increased heat generation as more air leaks out, I think you can see how it is possible to get to a point where there is something like a chain reaction or "runaway" temperature increase.

The above heat generation can also result in the polyester experiencing a rise in temperature with the associated loss of strength. You have seen the effect of high heat by holding a match near the end of a piece of Nylon or Polyester and see the textile melting. In the steel body ply tire the increased bending can result in a fatigue failure of a steel cord. You can test the fatigue with a steel paperclip. Simply bend the paper-clip a few times and it will break. In the case of a tire, the number of bends to failure can easily be in the thousands.

I will cover the "explosion" in an upcoming post.

##RVT793

Monday, May 1, 2017

How tires are built -- now and in the past



First video is of  overall process of manufacturing a tire.

Next is how tires (in this video from the 1930's) were made.

Then how larger farm tires were and in some cases still are made.
 
Bias tires in U.S. in '60s and in third world countries today.

State of the art tire assembly machine. This would be what you would see today for passenger and LT. The process is similar for truck (RV) tires being made today with just a little less automation by top tier tire company.

And I bet some just thought rubber was squirted into a mold.


Subscribe to the weekly RVtravel.com newsletter or one of our other newsletters about RVing. Great information and advice. Now in our 16th year. Learn more or subscribe.

##RVT792

Monday, April 24, 2017

How fast can an ST tire run?


Monday, April 17, 2017

Question of running year old tires or Running less than max psi

Question from Chris

Hi Roger,

I came across your website by way of referral from a member on a Keystone RV forum.  I have a concern regarding upgraded tires and wheels for a Keystone trailer I own.  

As most manufacturers continue to cut costs in value models, wheels and tires seem to be ground zero in their savings.  So, to help mitigate tire failure on my coach, I've upgraded my china bomb OEM 14" tires sized ST205/75R14 LR-C to ST225/75R15  LR ? and purchased new wheels to accommodate the new rubber.  My wheels are Sendel wheels that support 2540 lbs of load each. 

I purchased Carlisle Radial HD tires in LRD from Discount Tire.  Unfortunately, they received LRE tires in instead of the LRD tires.  The Discount Tire salesman quickly resolved the error and within 2 days, had LRD in stock.  I returned to the store to have them balanced and mounted on the wheels. The stock they received in had DOT date code of 1516. He told me that was the newest in all his warehouses. I didn't want year old tires so I rejected the sale.  

Then, I ordered the same tires from Walmart.com.  Same story, the DOT date code was 1616 and 2016.  Rejected that sale.  Finally, I ordered them from Amazon.com.  They arrived today.  Again, tires are around 1 year old and I'm sending them back.

My first attempt at ordering tires from Discount Tire resulted in LRE tires. They were much newer around Nov 2016. I think my quest for load rated D tires from Carlisle in size 225/75/15 is futile.

So now, I'm considering purchasing the LRE tires as I think the local stock is much more fresh than I can ever find with LRD. The only limit I have is my wheel capacity at 2540 lbs. If the LRE tire max inflation pressure is 80 lbs supporting 2830 lbs, will it compromise the tire if I inflate only to 65 lbs (in order to stay within the specs of the wheel)? The OEM tires were LRC on 14 inch wheels supporting only 1760 lbs at 50 lbs. Weight is not a concern as I will never come close to max weight limits with my trailer on either LRD or LRE tire. 

Another thing that worries me is the stiffness in the LRE rubber. Comparing the Carlisle LRD to the OEM Trailer Kings is night and day. The tire is just so much more beefy. Don't really want to rip apart the trailer because it's rolling on unforgiving rubber. 

Any opinions and recommendations is greatly appreciated.

Thanks in advance.

Chris M.
Concerned RV owner
+++++++

My answer:

OK you have a couple different issues.

You need to know that tires are made in batches. For relatively small markets it's possible that a company may only make an item once a year or even less frequently. While tire age is of concern when the tires are on the ground and exposed to sunlight and heat, it's less of an issue when in the factory warehouse.

One way to let your mind rest a bit is to ask when the warranty clock starts ticking. Some companies clearly state on day of application or first retail sale. Others say the warranty is based on DOT serial. If it's based on date of sale and clearly stated as such in the literature, I would be less concerned and just be sure that the sales receipt has the date and DOT serial of each tire identified and keep both warranty and receipt in a safe place.

Now, since you have taken the step of going from the ST205/75R14 LRC to ST225/75R15 LRD, you have increased the load capacity from 1760 @ 50psi to  2540 @ 65 psi. You have increased the reserve load capacity by over 50%, which should deliver very reliable service. While I do not have any data to go on, I think that when inflated to the same psi the LR-D and LR-E would have similar stiffness. It's the air that supports the load and it's the air that provides the majority of the tire stiffness.

For your application I would think there would be no problems with running LR-E tires at the wheel limit of 65psi.

So, bottom line, I think you can go with the year-old LR-D tires or run the LR-E at 65.

Monday, April 10, 2017

Why isn't my TPMS accurate?

Comment on an RV forum
"I just bought a new TST 507  TPMS (tire pressure monitoring system) and  I gotta say they could improve the documentation.
Definitely confusing as setting up is a bit complex. At one point you are told to press a button and wait for the second beep (not the first!) before setting the pressures or whatever.
But once that's over, it works as advertised. It does seem to take a while, once turned on, for all the sensor readings to be displayed. After that it just cycles through them every 5 s, and beeps when one is over or under.
Not sure how accurate the psi readings are. Will have to get out my pressure gauge and compare."
+++++++++++++++=
My reply

TPMS are primarily designed to WARN of a loss in pressure and are not intended to be your primary source of accurate pressure measurement. In my experience ALL TPMS will have one or more sensors reading a psi or two different than a hand-held digital gauge. For that matter even hand-held gauges are seldom accurate to +/- 1.0 PSI based on the calibration checks I offer at my tire seminars.

IMO best practice is to set your tire pressure as close as possible to the desired CIP (cold inflation pressure) using your personal, master digital hand gauge and then install the TPMS sensors. Wait about 5 min for pressures and readings to stabilize, then do a pressure check on the monitor. You will note slight variation, but all should be within the specified range (some spec +/- 2%  some spec +/- 2 psi) You will find that after a few days use you will get comfortable with the pressure readings showing some variation from each other. With a little experience you will get comfortable and know the range of normal variation.

What I do...
Each morning when I get up, I first turn on the TPMS monitor and go get my coffee. By the time I am done with the 1st cup - about 10 min - all the sensors have sent in a reading. I step through each tire on the system and based on experience, I know if the tires are ready to go as far as being properly inflated. Yes, the numbers vary, but as long as they all are in a range of a couple psi from what I got when I last set the tire pressure all is good.

With the above practice I am getting the "cool tire" pressure reading which is the only reading of importance. With my +10% over the minimum inflation needed for my Motorhome, I don't have to worry about a daily +/- 2 to 4 psi variation. However, if I have a few days in a row with the display pressures consistently showing a few psi lower than my CIP goal I know it's time to plan on a stop at the truck stop for a shot of high pressure air.

##RVT789

Monday, April 3, 2017

What is a good tire gauge?

You need a system, as any gauge can be damaged or fail.

Pressure gauge system
Over the past six years I have offered pressure gauge calibration check services. With well over 70 gauges of almost every description checked we have learned that many are not much better than door stops or for use as a tent peg.

There are some broad generalities we have learned.

Digital gauges
are usually the most repeatable and accurate with dial gauges.
Next are "stick"
or "pencil" gauges lagging far behind.

While it is also true that I have found some gauges of each type to be accurate, those tend to be those that are brand new. The stick gauges with the sliding bar tend to get worse with age. This is probably due to dirt and nicks in the slide stick causing inconsistent and inaccurate readings.

Before I get into my suggested "system" some are probably wondering how I can be confident that my master gauge is itself accurate.

Having worked as an ISO 9001 certification auditor, it was part of my job to understand how to establish systems and procedures that when followed could be relied upon to deliver accurate information. Even though I am retired, I still can gain access to tire laboratory test equipment and occasionally compare my gauges to current ISO certified laboratory gauges.

System:  You need at least two gauges. One is your own personal "Master Gauge". This gauge is not used to check the pressure in your tires. It is only used as a reference for your regular use hand gauge. The Master gauge should never be stored in your tool box but should be carefully packed away where it will not get dirty, wet, dropped or knocked around.

Calibration check procedure: Using one of your front tires as a source of high pressure air you would take a reading with your Master gauge and a reading with your hand gauge. Hopefully when you first set up your system they will both read within 1.0 psi of each other or better. If not you may want to check your gauges against other digital gauges to try and confirm if it is your master or hand gauge that is most accurate. Majority wins if you have two that match to within 0.5 psi. For your two gauges you should record the two pressure readings and the date. You can then take readings of all your tires using your hand gauge, recording the pressures as you go. You could also record the readings of pressure from your TPMS (tire pressure monitoring system). Now I would expect the TPMS readings to be within +/- 3 psi of your hand gauge.

Remember, TPMS are primarily a tool to warn when there is a change not to be used as an absolute accurate gauge. Again record the measured pressures. Once you have finished this initial check you can set your tires to their appropriate Cold Inflation Pressure (CIP) level using your hand gauge.

Now when you look at your morning TPMS CIP readings, you should see similar movement up or down of the pressure of all tires as daily morning ambient temperature changes. Remember the tire pressure will change by about 2% for each change of 10F ambient. I covered this change is THESE posts.

As time goes on you might see a slow decrease in pressure. This is due to air permeation through the tire carcass and O rings around the valve and TPMS sensor. Eventually after losing about 5 psi you should "top off" the tire pressure. At that time you would use your hand gauge to set the tire pressures. I would suggest that before setting the tire pressures you again do a gauge comparison to learn if there has been any change in the accuracy of your hand gauge. If the difference between the two gauges has changed then you need to learn why.

Reliability: It is very unlikely that both your master gauge and your hand gauge would both go out of calibration by the same amount and in the same direction at the same time.

My System:  I use an Accutire MS-4021B


Digital Tire Pressure Gauge that I bought from Amazon for $12 as my master gauge. (Note I confirmed this gauge is off by 0.5 psi.)  I also use one as my hand gauge (seen above). Since this gauge does not have a truck "dual foot"
head I also run hose extenders on my rear duals. 
I also bought a Tire Traker TPMS. 

I have not had any leaking problems as I check the valve stems, TPMS sensor and hose fittings with a spray of soapy water to ensure there are no leaks.

Some may want to save $12 and not bother with having a master they can trust. But I don't think it's too hard to imagine a gauge reading a bit higher with time as the internal springs lose strength, so you would get misleading high readings which means your pressure is actually lower. This can lead to a failure that will cost a lot more than $12.


All information on this website is copyrighted by RVtravel.com. Our offices are located at 610 5th Ave. S, Ste. F, Edmonds, WA 98020. Write editor Chuck Woodbury at Chuck(at)RVtravel.com. Any information gathered by visiting this website is kept private and never sold or shared with outsiders.

Monday, March 27, 2017

Question on Sidewall "bumps"

This topic concerns a potential SAFETY issue so is a bit more involved as it is important that everyone understands the situation.

Smitty asked:
I have 5 1/2-year-old 12R Michelin XZE tires on our coach. No cracking, and have performed well.

I found sidewall 'bumps' (Tire Center gent, said they're not 'bulges', as they're so slight). One maybe 3/32" of a protrusion, the other much less. The gent said they could be belts that are misplaced or broken. But he also said the XZE's have a thicker sidewall, and that the outer layer of the tire could have separated.


I know it's hard to give advice based upon a description, but I wanted to ask your thoughts on the opinion given to me by this tire gent.


He suggested that I monitor the size of the 'bumps' daily, and if they don't grow, he felt that they were safe to drive on. He commented that the tire was so overrated for what it was carrying weight-wise on my RV, that it was not working hard.


I've always thought that once a tire starts to break down, it was at risk for a catastrophic failure?

 
The tire was not unmounted for inspection, but if it was an outer layer separation, as he said it could be, how would they be able to see this?


Opinion? At 5 1/2 years of age, is it worth even considering monitoring and watching for growth? Or just replace and move on? 


+++++++++++++++++
Here is my reply:

First off, I do not feel that sidewall "bumps," "bulges" or "protrusions" occur because of misplaced or broken belts. Belts are under the tread not on the sidewall so I have to wonder what training, if any, the "gent" at the tire store has received on tire construction or inspection procedures. Also not sure what he is talking about as the "outer layer" of the sidewall. In a truck tire there is basically the thin innerliner (a bit like having a tube as part of the tire), then body ply, then the sidewall. So, if he thinks the sidewall has separated, then the tire has failed and should be replaced.

Now, some fact-based observations on sidewall bulges or outward protrusion vs. depressions that are inward toward the air chamber and are indications of two completely different causes.

The inward depressions can occur once or twice around almost any radial tire. If you take a close look in full sunlight of smooth sidewall tires you will see depressions that might be about 1/16" deep and 1/4" to 1/2" wide in the circumferential direction. These are caused by the lap splice of body ply material that provides more resistance to the slight growth seen in all radials due to inflation. These depressions will run a radial direction from the wheel to the tread and seem to disappear as you get near the tread or near the wheel. These are normal and I would only consider them minor cosmetic features of a tire.

An outward bulge may be 1/2" or as large as a couple of inches in the circumferential direction. The larger or more distinct, the more concerned I would be about the durability of the tire. Usually bulges are the result of some impact damage done to the body cords that resulted in a few being broken due to shock loading.

Here is a blog post I did with pictures of bulges and depressions to help people understand.

Here is a post on an Impact Failure I had on my personal car.

Now on some with small features, the eye plays tricks as to it being a bulge out or a depression in. I have even seen instances of two depressions being close together such that the normal sidewall between the depressions gave the appearance of being a depression. The simple tool to use is a ruler or straight edge and to lay it across the area of interest. This will quickly identify if you have a bulge or depression.

What to do:
Review my blog posts above.

You might also find a different dealer. A simple Google for "Truck Tire Dealer Town" where "Town" is a nearby larger community, should give you a number of options. For 19.5 and larger size tires I would only deal with a Heavy truck Center.

You might also contact Michelin at their Customer Contact on their RV tire page for a suggested location with people sufficiently trained in tire inspection to pass judgment on your tires.
http://www.michelinrvtires.com/reference-materials/
You can tell them that you're not happy with the inspection you got from the tire guy as they don't seem to understand the basics of rtuck tire construction. 

##RVT787

Monday, March 20, 2017

Am I reading Load & Inflation tables correctly?

Wayne M. asked

Tireman, Here is some information on my Toyo 265/75R22.5 LR-G tires. Can you confirm I am reading the tables correctly?
Toyo 265/75R22.5
PSI     70     75     80     85     90     95    100    105   110
Dual 3625 3705 3860 4040 4205 4410 4525 4685 4805(G)
Sing 3875 4070 4300 4440 4620 4805 4865 5150 5205(G)

Measured scale weights on each corner
RF: 4650        LF 4750
RR: 9000       LR 8250

Right side has Refer. There isn’t anything in the bays (not all the way through bays) that I could possibly switch around for even distribution so I have to go with the heavier weight.

I’m thinking 100 psi for the front.
What would my rears be with a fudge factor?

++++++++++++++++++++

First off , I have to thank you for providing the information on your specific tires and your actual tire loads for each end of your axles. I prefer data to guessing.

With 4,750# on the heavy end of the front axle we see that 95 psi can support 4,805 so that would be the MINIMUM Cold Inflation Pressure for your fronts (remember all tires on an axle should have the same CIP) and I suggest you add 10% (10 psi) cushion to get 105 psi CIP on the fronts.

The rears are dual, so looking at those inflations.  9,000 divided by 2 gives 4,500# per tire, with the 90 psi being the minimum inflation needed to support the measured load. Adding 10% or 9 psi gives us a suggested 99 psi. 100 is easier to remember and measure so lets go with 100 CIP on each of the 4 rear tires.

Comment: Please always adjust inflation up and avoid going down no matter how close the weights are.

##RVT786

Saturday, March 11, 2017

Question on Maximum tire pressure

Got an email stating the writer was concerned and a bit confused on the Maximum inflation a tire can have. He had heard about people having "Blowouts" and after installing a new TPMS and seeing the pressure increase was concerned his tires might explode.

I can understand the confusion as people read the tire sidewall and in some cases see the words 'Max Inflation". This is NOT the max operating inflation but in reality is the inflation needed to support the max load the tire is rated for. It is also important to remember that unless a tire engineer is specifically talking about "hot inflation" we are talking about the "Cold" tire inflation when the tire has not been warmed by either running or being in direct sunlight over the previous couple of hours. Technically this means the tire is the same temperature as the surrounding air or "AMBIENT" temperature.

I previously covered the effect of temperature on tire pressure and the "Ideal Gas law" so we know that for each change in temperature of 10F the tire pressure will change by about 2%. This means that when the tire temperature increases by about 50F we can expect the pressure to also change by about 10%. We need to remember that the TPMS sensor is being cooled by outside moving air so the hot spot on the tire is actually much warmer than the indicated temperature. This is one reason why we many times see pressure increase by 15% or more.

True tire "Blowouts" are usually caused by too low a pressure which flexes the tire sidewall and results in fatigue failure of the steel body cord or melting of the Polyester cord in LT, P, or ST type tires. The separation of the tread and belts is sometimes mislabeled a "Blowout" which leads to confusion. Separations have a different cause than simple loss of air pressure.

Back to the original question. Tires are designed to handle significant increase in pressure, most in the range of 200% of the pressure marked on the tire sidewall.

BOTTOM LINE Always ensure your tires are properly inflated and the use of a TPMS is, in my opinion, the best way to  not be surprised by a puncture or air leak.


Send your questions to me at  Tireman9 (at) gmail.com


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##RVT785

Sunday, March 5, 2017

Question on TPMS settings

Got this question:  "Tireman, I would like your opinion as to what would be good alert values to set in the TPMS on my trailer. I need to set high and low pressures and temperature alerts."

First lets be clear that Trailer Cold Inflation Pressures and Motorhome and Tow vehicle CIP are established differently.
While I have covered the specifics and the Why for each application in other posts, I will summarize here.

1. Both trailers and motorhomes need to confirm the actual load on their tires by getting on a truck stop scale or similar when the RV is fully loaded.

2.Using the Load & Inflation tables published by tire companies we should all learn the MINIMUM inflation needed to support the measured load for each tire.

3. Motorhomes should set their CIP at the MINIMUM Inflation in #2 + 10%

4. CIP for Trailers is the the pressure on the tire sidewall.

5. The Low pressure alert for Motorhomes and Trailers should be the MINIMUM inflation needed to support the measured load.

6. Trailer tires should not be loaded morer than 85% of the "Max Load" as molded on the tire sidewall.

7. Most TPMS come set with the max temperature warning at 70°C ( 158°F)  which is just fine.

8. Based on input from many RV owners with TPM I would suggest the High Pressure warning be at least 25% higher than the CIP.

Send your questions to me, Roger, at Tireman9 (at) gmail.com


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Tuesday, February 28, 2017

Question on tread scrubbing on trailer tires.

Got this question:
"I have a question regarding interply shear or scrubbing common on double or triple axle fifth wheels. I have a double axle and try to avoid sharp turns and U-turns as much as possible, but I see visible signs of scrubbing on the tread of my tires. It looks like flat spots on the edge of the tires. After a turn, I can go back and see the rubber I've scrubbed and left on the road. It's frustrating. I have the axles aligned and tires balanced once a year and have individual wheels weighed occasionally. I try to keep side-to-side and front-to-back weights within a couple hundred pounds. I currently carry 85%-90% of load capacity, or about 3300-3400 lbs per tire.

"My question is: Would going to the next load range up (from G to H) or going to a harder compound tire reduce this problem? I currently use Goodyear G614RST tires, size LT235/85R16. I've heard in the past that Michelin uses a harder compound in their tires, which makes for a little stiffer ride, but might this overcome some of the effects of scrubbing? I feel I could get a lot more miles out of my RV tires if I could reduce the flat spots or sculpting caused by unavoidable scrubbing."

My answer:
Axle alignment or wheel balance isn't the problem. There is a sketch in this post on interply shear that shows why the tire tread scrubs. The center of tire rotation is not pointed to the center of the turn radius so the tires are always being dragged around every turn. It is just worse on tight turns.

Lowering the percentage of max load capacity is a good idea. Don't forget that it is the air pressure that determines the load capacity not the Load Range (G to H). You will gain nothing from a Load Range change if you do not also increase the air pressure. You do need to confirm the wheel max psi capacity which, for some wheels, is not easy to do as some wheel manufacturers do not have high pressure ratings easily available.

Regarding tread compound: Sometimes it isn't just the hardness of the rubber but also the tread pattern that can affect scrubbing wear.

In general, the tread scrub is a function of dragging a trailer around.

Send your questions to me, Roger, at Tireman9 (at) gmail.com


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##RVT783

Thursday, February 23, 2017

Q&A on 5th wheel trailer and tow vehicle, and an announcement

 Dear Roger,
"I pull a fifth wheel trailer. When I am towing, I inflate all tires on the truck and fifth wheel to their max load pressure. The truck tires are load E, Max psi is 80. The fifth wheel tires are load G, full steel belted with max pressure 110psi. Weighing the rig at Cat scales shows me that the weights on the axles are not heavy enough to warrant using the maximum pressures. I would like to inflate the tires so that the psi matches the actual load. Is there a way to calculate this? I have scoured the internet and cannot seem to find any tables that would give me a clear answer. Thank you for your advice."

My answer:
Hi. There is much information in this blog that can answer your question and provide good background. But I'll provide some info here so you can get on the road with proper inflation. You can then review the info on the blog as time permits.

First we need to separate the tow vehicle from the trailer as the tires are different and the forces on the tires are also different.

Trailer.  Due to the fact that trailer tires are basically being dragged around corners rather than steered, there are forces called "Interply Shear" that place much higher forces on the belts of the radial tires when in trailer application as opposed to when on a motorized vehicle such as a motorhome or tow vehicle. You did not offer the actual measured loads on the trailer tires or the tire size so I can only offer general guides.  Be sure the load capacity of the tires at the inflation you are running is at least 10% greater than the measured load with 15% better. Were the LR-G tires the OE size and load range or did you upgrade to larger or higher?

Tow vehicle:
If you are running the OE size and load range your owners manual should give recommended minimum inflation levels for a loaded vehicle. Many pickup trucks offer "full load and light load" condition inflation recommendations. I recently (Feb. 15) did a post on tow vehicle tire inflation. I suggest you review it and let me know if you still have questions.

You also asked about load and inflation tables. Here are 5 posts on that topic.

* * *

Now, some of you may feel that a more detailed reply would have been in order, and I agree. However, it's very difficult to provide a more specific answer without more information. This brings me to the "Announcement" portion of this post.

With almost 260 posts in this blog, I've covered most features and topics but after reviewing the posts some people still have questions. So I'll do my best to try and provide specific answers. There are a few specifics that I will need in order to provide a useful reply.

With thousands of possible tire/vehicle combinations there is no way I can know the specifics of them all. So I will need your help. When you send a question please provide as many of the following details as possible:

•Tire size, including the letters in front of the numbers if any.
•Load range or the tire max inflation.
•Measured load on each tire position or each axle. If scale weights are not available then GAWR from the tire sticker/placard
•Specific application, i.e., trailer, motorhome, car, pickup
•Tire DOT if the question is about tire age or country of origin

Send your questions to me, Roger, at Tireman9(at)gmail.com


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Wednesday, February 15, 2017

Tow vehicle tire question

Dear Roger,

"Last week I purchased new E rated tires for my F150. Went with the BF Goodrich KO2 (275/65/18) and so far I'm very happy with them. These are larger than the tires that came from the factory (265/60/18). I have a quick question.

"The tire shop originally put the PSI at 35 based on the door sticker, but after reaching out to BF Goodrich they suggested 45 PSI for everyday driving. They didn't give any recommendations for tire pressure while pulling a trailer since there are so many variables like trailer size, weight and cargo. The tire shop suggested going to 50 pounds and then deflating back down after the trip. I'm just curious if others actually bump up their PSI while towing, and have you noticed a difference in doing this? Just trying to figure out if there is a benefit to doing this.

Some important information is missing, so let's identify our assumptions:

1. We are talking about the tow vehicle tires - the F150.

2. The original poster didn't identify the OE (original equipment) tires as being P type or LT type. This makes a major difference and providing that information up front will eliminate guesswork for those trying to help with the answer. With a 35 psi door jam sticker number, I suspect the OE tires are Passenger type and the replacement tires are LT type.

3. Since it is the air pressure and not the tire construction that supports the load on a tire, buying LR-E (80 psi) tires when you never run higher than 65 (LR-D) would be a waste of money. Also if you are changing from P type tires with a max inflation of 36 to 41 you need to confirm the wheels are rated for higher load and inflation of LT tires.

4. The door jam pressures are based on the car company making some estimates on how much and how often you have the vehicle empty or fully loaded. You might check the owners manual and see if they give an empty and loaded tire inflation suggestion. The inflation in the OE tires is what is needed to support the GAWR but few people run that heavy all the time with their pickup.

5. I suggest you get the F150 on some truck scales when empty and again when fully loaded with the trailer also fully loaded, and learn the real facts of the various axle loads under both conditions.

6. Knowing the real loads, you can use the tire Load & Inflation tables to learn the MINIMUM cold inflation pressure for the F150 for the two situations. I suggest you use a margin of +10% of the table inflation to establish your CIP (cold inflation pressure). See other posts on weight and inflation if you need more details.

7. Trailer tires are a completely different situation and should always be inflated to the tire sidewall inflation. You should also run no more than 85% of the trailer tire max load rating when on a scale. Cornering, sway and side wind loads have been shown to shift loads side to side by 10% or more. Also the Interply Shear on tires in trailer application needs to be considered as this is a major contributor to trailer tire belt separations.

Hope this info helps clarify.




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##RVT781


Monday, January 23, 2017

Quick post on RV weight

Read a question on an RV forum about "4-Corner weights vs. just getting axle weights." Here is my reply.

Getting 4 corner weights (actual load on each tire for trailers or each position on motorhomes) is definitely worth doing, once. Once you figure your numbers you are typically good to go for the life of the tires or unless you change something big.

Do it fully loaded,  i.e., fuel, water, canned goods, fishing gear, clothes, books, people, etc.

Based on actual data from RVSEF, very few RVs have side-to-side loading at 50/50%. Some owners have discovered one axle end as much as 1,000 lbs. heavier than the other!

Once you know for a fact that you have at least a few hundred pounds "cushion" (being under your RV GAWR [gross axle weight rating] and GVWR [gross vehicle weight rating]), you don't need to do corner weight again unless you make a major change or remodel of the RV (e.g., adding a residential fridge or granite counter-top) and have a reasonable balance to start with.

I do suggest at least once a year a quick check of axle loading by going through a truck stop scale. You can compare the truck scale numbers with your corner weight totals to confirm your RV hasn't suffered from weight creep, as some of the drivers may have noticed over the years.


Weight terminology tidbits:

SCWR (sleeping capacity weight rating)

The manufacturer’s designated number of sleeping positions multiplied by 154 pounds (70 kilograms) which is the official weight of people in cars and RVs.

CCC (cargo carrying capacity)

The GVWR minus each of the following: unloaded vehicle weight, full fresh (potable) water weight (including water heater), full LP-gas weight, and SCWR.
This new label permits the buyer/owner to determine the carrying capacity (CCC) based on a personal calculation of actual passengers carried, the amount of fresh water onboard, and the amount of LP-gas carried.

More info on terms and abbreviations can be found HERE



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Monday, January 9, 2017

Want better quality tires on your RV?

Many people want to complain around campfires or on RV forums about the poor quality of various components on their RV. While I can't address systems such as Refrigerators, Holding Tanks, or Furnaces, I can comment on the quality of tires selected for placement on RVs.

With an industry that focuses on quantity and low cost, is it any wonder that tire performance isn't as good as we would like? We need to remember that while there are laws specifying the minimum performance and capabilities of RV tires, I am not aware of any legal requirement against providing tires that can support more load than the minimum requirement or with speed capabilities higher than what most feel is a reasonable and safe operating speed for large RVs and/or trailers.

I have written a few times about how to file a complaint with NHTSA (National Highway Traffic Safety Administration, the federal agency that establishes minimum performance requirements for tires) and you can easily find those posts using the list of links on the left side of this page.

I feel this topic continues to be important given recent posts on RVTravel.com and rvdailyreport.com that have been on the low quality of RV components.

I just read a post from a fellow RV owner that had a couple of tire failures. When I asked if he filed a complaint with NHTSA, he said: "Couldn't report anything. We were on the side of I-95 middle of nowhere going south. All I know is tire blew out on inside, there was a hole. Front passenger tire."

So, because he no longer had the tire he can't provide the info needed by NHTSA for their database.

I replied: "Well, that's a perfect example of why it is important for everyone to have a written record of the tire DOT, size and brand info on file with other important information you keep for other components of the RV such as Refrigerator, Furnace, Generator, TV, etc.

"Many complain about the poor durability of tires in RV application but very few bother to take the basic steps needed to get the information to the DOT. NHTSA (department of DOT) can investigate products if there are sufficient complaints received, and if they find an automotive component doesn't meet the required standards they can order a recall. Recalls can result in replacement tires being given to owners.

"However for a complaint to be minimally helpful in establishing poor performance the full DOT (including date code) is needed. All too often there is confusion in the terminology of tire company, brand and model. Some owners do not provide the correct or complete tire size, giving info such as 225-15 for example.

"I have a number of posts on my blog about recalls and NHTSA if people want to learn more.

"If not interested in getting better-performing tires on your next RV, that's your choice. But I have little compassion for people who have problems but aren't willing to spend 10 minutes filing an actionable complaint. Remember a bit@# session around the campfire or on an RV forum will never result in an improvement in RV component quality."


I have also read an account of an RV owner who did file a complaint and apparently the tire importer read the NHTSA report and the guy ended up getting a set of tires free. Now, this is very unusual but it did happen. But again, if you don't have the DOT S/N, I do not see how you can file a complaint, and if you don't file complaints why would you expect there to be a recall?


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