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Saturday, May 31, 2014

What is the Best Trailer Tire?

I frequently get asked "What is the Best tire for my trailer?
I don't want another blowout"

My answer:

 I previously did a post on "Best Tire".

Sorry there is not enough data to provide a more focused answer.  I am sure some are hoping I would provide the one size and one brand that will solve all their tire problems.
I would point everyone back to this link from an RV forum with data from NHTSA. As you can see the numbers of RV owners that make the minimal effort to file a complaint sends the message to NHTSA that there are no significant problems with RV tires. I also know from looking at some of the complaints the quality of the information is spotty even if a complaint was filed.

Examples include wrong size, wrong tire brand, missing or incomplete DOT serial. Expecting information on actual load, speed etc is unrealistic and expecting an accurate description of the real failure is just a dream.

Engineers react to and work with facts. I have been trying to educate a few folks on another forum that melted body ply cord, as seen in tires with a Run Low Flex Failure

is physical evidence of a tire having been run under-inflated at highway speed. The discussion ended with one poster accusing me of hiding the facts and lying to keep my job. Of course he had no idea why the body cord melted but was certain I didn't know either. That ended my participation on that thread.

I know of no data to indicate that anyone is intentionally making "bad" tires. I do know of data that confirms the majority of RVs have tires in overload and that a significant percentage of tires on the highway are under-inflated. I share with others the  personal observations that a good number of trailers are exceeding the speed limit of their tires.

Multi-axle trailers place unique and high side loading on tires. This cause internal forces that contribute to the short life for tires in this application. This is a fact based on engineering and all tires are subjected to this type of structural load. It is just a fact that multi axle trailers are worse than single axle RVs.

Bottom Line
If you want to minimize the probability of having a tire failure on your multi-axle trailer, all I can suggest is you read my post on "Best tire", inflate your tires to the sidewall inflation 100% of the time, at least once confirm your side to side and axle to axle unbalance is not giving you an overloaded tire, use TPMS w/metal valve stems and do a free spin inspection at least once a year and cover your tires with WHITE cover whenever parked in the sun for more than a day. You will probably still only get 4-5 years out of your tires because of the internal stress load but hopefully they will be 5 years with no problems.

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Friday, May 23, 2014

What is the "Best" TPMS

Yes along with   What is the "best" brand tire or Best RV or maybe even the Best pizza, people seem to think that there is a single answer to almost every brand selection that everyone will agree on.

 As an engineer I feel that just as Henry Ford was wrong when he decided everyone would want a black car, there is seldom a "Best" anything that is the best for everyone. However, having said that, you probably still would like some guidance in selecting a TPMS.

NOTE: I am certain that ANY brand TPMS is better than not having a system.

So here is what I suggest you use for a selection system. I think this will be a good system to use even as the technology moves forward.

I think there are four major categories to use when shopping for a new or replacement system.

1. Performance:  What does the system do and how well does it do it?

2. Cost:  This includes more than just the initial purchase price as there may be the cost of installation and what about the batteries?  When looking at cost I suggest you do a comparison based on the expected replacement cost of replacement sensors if you can't install batteries yourself.
Example - non-replaceable batteries last 5 to 6 years so include the cost of a set on new sensors vs the cost of replacing batteries every two or three years. (three sets at $1.50 per battery for example). Selection of an internal mount system will include the cost of the initial dismount and mount and balance of tires and a second dismount, mount and balance when the sensors need replacement a few years later. This cost could exceed the cost of a TPM system so is an important consideration

3. Warranty:  This may be the easiest as I prefer a longer warranty to a shorter one. I believe that car manufacturers do a much better job of designing and building their product than does the RV industry. Given the prevalence of 3, 5 and even 10 year warranties for cars vs the normal  few months offered by those selling RVs products with longer warranties are more likely to be better than those with short warranties.

4. Support & Service:  How easy is it to contact the seller? Are there videos on YouTube showing how to install and program your TPMS?

Items 2 through 4 are best left to you to learn and investigate. Some people don't care about YouTube videos and others don't worry about warranties, so lets focus on "Performance"

Here are some questions to consider:
a. Does the system "talk" to your on-board video display? This may lock you into one brand to the exclusion of all others.

b. Accuracy:  Some people are overly concerned with the accuracy of the TPMS. Personally I have observed that after setting my tire cold pressure using by calibrated digital hand gauge I see that the TPMS gives slightly different numbers for almost every tire BUT the difference is usually only a couple psi. While this may be measurable I don't consider it meaningful. You might want to review the concept of Measurable vs Meaningful. You could also review my comparison of two systems HERE.

c Temperature vs pressure checking. Most aftermarket systems will signal both pressure and temperature. Some people think temperature is very important but as a tire engineer I believe that if you have the proper load and inflation you do not need to worry about temperature variation and can expect to see operating temperatures range from +15°F to +50°F above ambient. Many TPMS have a warning temperature of between 150 and 160°F which is OK in my opinion for a warning level. It is very unlikely for you to have a tire get hot without having a loss of air precede the increase in temperature.

d. Early warning:  I consider this an IMPORTANT and desirable feature
Imagine your cold pressure is 100 psi. Your low pressure warning is probably -15% or 85psi. When driving you might have a hot pressure of 120 psi. Now suppose you get a leak from a puncture or possibly a valve stem gasket leak. Would you rather get a warning when you loose 3 or 6 psi over a few minutes down from the 120 psi HOT pressure, or would you think it OK to only be warned after you loose 35 psi down from the hot pressure to the "Low Pressure Warning" level.?

In my opinion getting that "Early Warning" allows you to slow down and start looking for an exit or safe place to pull over as you monitor the air loss over then next 5 to 20 minutes you might have before you get down the the minimum pressure needed to carry the load.

Sometimes the rate of air loss can start small but increase over a few minutes as the hole in the tire gets bigger. If you only get the single warning it may already be too late to save and repair the tire.

I hope I have given you some things to consider when selecting the "Best for you" TPMS.

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Saturday, May 17, 2014

Question on UV & Ozone tire damage.

Got this question and thought I would share my answer
First of all, thanks for all your informative comments here, and also for the mounds of useful information in your blogs.
Have a question though... I've always thought that damage to sidewalls from ozone (which is always in the atmosphere) is going to cause sidewall damage more quickly than UV rays. Therefore, unless your motorhome spends a significant amount of its life in direct sunlight (as it might if you were full-timing or even half-timing), it really doesn't matter much if you cover the tires, since you are going to be replacing them in 7 or 8 years anyway. Is this faulty thinking?

Yes Ozone can do real damage to tires. I have seen sets destroy because they were parked in a garage that had a leaking Ozonator.  BUT Heat is the primary killer of tires.
Ozone and UV can only attack the rubber surface but heat damages the internal components and structure in addition to the surface rubber.
The UV protection test in the link above shows how almost anything can stop the UV damage to tires.

The stuff sold that promises UV protection is like suntan lotion in that it may extend the time you can be in the sun without getting burned but I know of no spray on protection that cuts UV to zero.

 Heat accelerates the degradation of the molecular bonds which can lead to belt and tread separations.

I did a test on covers
that shows the significant increase in tire temperature. Since the affect of heat DOUBLES with each increase in temperature of 18F this translates to an effective doubling of the "aging rate" of tires (or reducing the tire life).

I cover my tires whenever parked for more than an overnight stay where the tires can be exposed to direct sunlight. The WHITE covers block all the UV and keep the tires at about ambient temperature rather than baking the life out of them.

With proper care:
Washing with same cleaners and cloths I would use on the RV body.
Having the tires "underloaded" by about 20% (a 20% Safety Factor if you like) when setting cold inflation.
Never getting lower that 5% above the inflation needed to carry the load.
Multi-axle trailers should run the tire "max" inflation unless they have significantly upgraded their tires with higher Load Range and larger size, but they still need to run a much larger "Safety Factor" due to the unique loading caused my their tandem axles.
Always running TPMS and checking pressure every AM and after each stop.
Using digital gauges that have been shown accurate to +/- 1psi.

I am hoping for 9-10 year life on my Motorhome. If I had a multi axle trailer and took the same precautions I would hope for 5 to 7 year life due to unique loading from suspension design.

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Tuesday, May 13, 2014

Tire Ozone protection

A question was asked about tires marketed as intended for "RV use" vs tires not marketed for RVs as it relates to both sidewall stiffness and UV protection.
   Tires made for use on US highways have a regulatory test they must pass. This "Rim roll off" test establishes the minimum side force a tire must resist before the tire comes off the wheel. Since it is the air pressure that carries the load, not the tire sidewall, two tires of same load capacity, size and inflation  will have very similar flexibility.

RE: Anti-Oxidants and Ozone and UV protection of rubber.
Unlike Sunglasses which can be tested for UV transmissivity, tire protection in done with internal chemicals.
Marketing claims of "More" or "Better" are in my opinion just PR as they never say better than what other tire. There is also an upper limit in the amount of these special chemicals tire companies can put in a rubber compound before other properties are negatively affected. There are also different chemicals that could be used. One tire company may choose chemical "A" and have 2% while another company may select Chemical "B" and use 1% but since chemical "B" is better then "A" less is needed for similar protection but "B" is probably more expensive.

I know of no recognized industry test that gives a meaningful comparison number for weathering and Ozone protection so it's impossible to compare different brands.

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5 year warranty on tires !!

We might be finally making progress.

An RV mfg and tire company have stepped up to address the issue of quality and reliability on RV trailer tires.
PrimeTime and Tredit now offer 5 year warranty.

Maybe you might consider printing out the Press Release and asking your tire company to match the coverage.

Subscribe to the weekly newsletter or one of our other newsletters about RVing. Great information and advice. Now in our 14th year. Learn more or subscribe.

Tuesday, May 6, 2014

HELP! We get tire "Flats" every year. or are they Tread Separations?

I got a question   "We have a 2012 43' 5th wheel Heartland Toyhauler, triple axle, have 235 80r 16 wheels and tires. Every year we seem to have at least 2 flats. This year we had 2 flats, going south, and by the time we arrived at our destination coming back north, (500+ miles) one of the tires were so rounded you could not stick your finger between the back and middle tire on the drivers side. We were very lucky they did not hit each other. We are wondering if we could put 12 or 14 ply tires on the same wheels? And if LT's would be better than the ST's?
Thanks for your help, 
Wife of very frustrated husband"

Dear "Wife of frustrated" I would be glad to help out. If you check my blog, you will see I cover a lot of different questions on RV tires.  My background is in the oldest post.
Now to your question.  I could use a bit more information.
You said you get a couple of "flats" but then describe a "rounded" tread which sounds like a tread or belt separation like
To me a "flat" just means you discover the tire has lost 20% or more of the correct inflation.
To be sure I have all the information I need, could you answer a few questions?
1. On your 5th wheel you have a tire placard (usually on outside of the RV toward the front of the driver side on the side of the trailer. This placard has tire size and inflation information similar to what is seen in attached Label. jpg. .There should also be some information from Heartland on the GAWR (Gross Axle Weight Rating) for your specific trailer in the stuff you got with your purchase. It might be 6,000# or similar number.

2. To confirm the tire size you are running you have "ST 235/80R16   LR-E"   The LR-E is Load Range E  The "ST" before the numbers is "Special Trailer" 
3. You might want to review THIS blog post on how to "read" a tire.
4. Is the tire inflation on your placard 80 psi?  Is that the inflation you set the tires to in the morning before travel?  You can learn more about inflation HERE.
5. Here is an important question. Have you ever had the trailer on a scale? The actual tire load is the 2nd most important thing to know with proper inflation being the MOST important.
6. What do you have for a tire pressure gauge. I prefer THIS gauge as I have tested them and found them accurate.
7 Do you have a TPMS to monitor tire inflation on your Trailer and Tow Vehicle?

LT type tires MAY be an option but we need to be sure that whatever tire you have can support the actual load on the tires.  The load on individual tires is NOT simply the load on an axle/2 and the load on an individual axle is NOT the total load/3.
Calculating the side to side load is something I can help with, and is needed if we want to know the actual individual tire load. BUT the individual axle load can be learned at any CAT scale or at most truck scales, or local gravel pits or grain elevators if you check Yellow pages or Google "Sacle Location"  where Location is your town or state.


I hope the above is informative as it outlines the basic information needed if you have a tire problem and would like some help.  Some people are more than happy to simply jump in but as an engineer I need FACTS and DATA.

I will post the information received and hopefully a solution to "Wife of frustrated" problems.