How old is too old ?

For RV application this is a tough question, because "It Depends".

Primary factors that affect the answer include 1. Type of RV -Motorhome, tandem axle trailer or single axle trailer.   2.Cumulative temperature i.e. How much time with tires below 60F  Below 70F,  below 80F  below 90F  Above 90F, Above 100F, etc up to Above 140F     3. Actual Reserve Load   4  If a trailer, how many times you backed into a parking spot  5. Do you use white tire covers or is the RV parked in full shade?

Ya, a lot to consider but each of the above items can shorten tire "life".  Would it be possible to construct a formula or spreadsheet with answers to the above to calculate the answer?  Yes but I doubt it would be worth the effort as the life of one brand or size would probably end up with different detailed factors. So let's just consider some of the items I listed so you may gain a better understanding of "tire life"

#1 Type of RV. This is where "Interply Shear" (a force that is trying to tear the belts off the body of a radial tire) Based on computer simulation this shear or tearing force is 20% or greater in tires applied to multi-axle trailers than if the same tire was applied to a motorhome, even with identical weight.  For those that care there are a number of posts on IPS on my blog if you really want to understand the background and how this force affects tires.

#2 Heat. This is the number one "killer" of tires if we set aside the obvious failures due to loss of air pressure. In fact, even the loss of air pressure results in excess heat that can lead to rubber reversion or even melting of body cord which leads to many "Blowouts".  Heat damage is cumulative and has a MAJOR effect on tire life. The reason for this is that rubber is always "curing". In technical terms, this means the molecules of Carbon and Sulfer are continuously linking, although at a slower rate when relatively cool 70F and below and the rate of chemical reaction doubles with each increase in temperature of 18F. I have a number of links to Scientific papers on the chemistry of tire curing in THIS post. It is also important to understand that the hottest area of a tire can not be measured with a heat "gun" or even with TPMS. Here is a graphic showing the relative temperature in different areas of a tire. The internal red area can be 20°F hotter than the rubber just 3/8" away and the range of temperatures in this example is 80°F so measuring at the correct location is critical as well as very difficult as it takes specialized needle probes.
 Also, this is the location of the highest level of Interply Shear.




#3 Reserve Load  This is the difference between a tire's load capacity at the cold inflation number in the tables vs the actual measured load on a tire.  Greater reserve load means cooler running temperature. See #2 above

#4 Backing into a parking space. This is something few think about but in extreme cases, the interply shear might get to 100% higher in a tandem axle trailer when doing a tight turn into a parking space. This high tearing force can initiate cracks in the rubber which can just grow and they never "heal) which can lead to belt separation many hundreds or thousands of miles later.

#5 Tire Covers.  See my post on using white tire covers.  Yes, this simply goes back to cumulative heat. See #2 above.

Long term readers of my may remember my post on how to maximize tire life.

One thing that is true is that Michelin and some other tire companies have set 10 years at the maximum life of a tire no matter what it looks like. This does not mean that no tire will fail due to "age" or the cumulative effects of the conditions I have outlined above. All of these conditions simply are shortening tire life from 10 years down to maybe as little as one or two years in extreme cases.

##RVT909

Do RV owners know about tire age?

There are many posts on how to learn the calendar age of tires by reading the DOT serial number and "de-coding" the last four digits to learn the week and year a tire was made.

But just knowing the calendar age doesn't tell you the useful life of a tire.

Some folks think ten years or longer is OK; others think it is a good practice to change every two years.

We each have different operating conditions which affects the "functional age" of our tires.

I arranged for a poll to be taken on RVTravel.com. It asked the question: "Have you ever heard the phrase 'Tires age out before they wear out?'"

I was pretty sure that many of you had heard the phrase, but now I have the numbers.

If you participated, Thanks!

When should you replace your tires? HOW OLD is too old?

A lot of folks talk about tire age and when they "age out."

Here is what a few tire companies have to say:

Passenger & Light Truck Service Life

Japan Automotive Tyre Manufacturers Association (JATMA) recommendation: At 5 years have tires inspected by "Qualified tire service person" and no matter the condition replace any tire at 10 years.

Bridgestone & Firestone issued a Tech Bulletin that supports the 10-year maximum but advises that "some tires will need to be replaced before 10 years due to operational conditions.

Michelin, Falkin, Yokohama and Vredestein suggest tires be inspected by specialist annually starting at 5 years and replaced at 10 years as a precaution "even if such tires appear serviceable and even if they have not reached the legal wear limit"

GM recommends tires be replaced after 6 years

Hankook says to replace tires 10 years after manufacture "even if the tire was never used"

Goodyear, Continental and Cooper do not give a maximum calendar age but stresses "Monthly Inspection" along with proper storage and monitoring of inflation pressure.

Kumho says to have tires inspected annually starting at 6 years and to replace the tires at 10 years, even if the tires appear serviceable.

Vredestein suggests tires be inspected by specialist annually starting at 5 years and replaced at 10 years as a precaution even if such tires appear serviceable and even if they have not reached the legal wear limit. They also say that tires on trailers, campers, horse trailers and caravans (motorhomes) be replaced at 8 years.


NOTE:
They are talking about the annual inspections after 5 years to be done by a "Tire Specialist", not just anyone that sells tires. I would suggest that when having this inspection done you ask for a written assessment as a minimum. You can ask if the dealer has an ATS Certified Technician on staff.

Tire info in Owner's manual and on Certification label

I have been looking at the "Tire Placard" AKA Vehicle Certification Label for a number of 5th wheel trailers. I learned a few things.

A couple of manufacturers have upgraded the tires on the newer units. Some went from ST235/85R16 LR-E to  ST235/85R16 LR-F. The inflation went from 80 to 110 so they are clearly offering improved load capacity or giving you a better margin above the tire capacity.

If you have an older 5th wheel and have either ST235/80R16 LR-E or ST235/85R16 LR-E you might want to check and confirm if your wheels are rated for 110 psi. If so, you might consider moving on up to LR-F and doing the slight up-size if you have the needed clearance as the 85 series tire is a bit larger in OD.

I also found one model that went from 16" to 17.5" wheels. It appears that the new RVIA 10% load margin requirement achieved some better than expected results. While this may not help out those with older trailers just knowing there are wheel & tire options available that are approved by your RV company could be considered good news.


On a related matter, I wonder how many of you have ever read the section on Tires in your owner's manual. I was surprised to see that some manuals have pretty good and detailed info. They cover stuff like weighing each side of the RV and not just the total on the 4 or 6 tires. While this isn't as good as learning the individual load on each tire a side to side comparison may identify some load imbalance. Since I suggest that trailers run the tire sidewall inflation we are not looking at calculating a minimum inflation. BUT we still want to be sure you have at least a 15% margin on load, so you should use the heavier side of the RV when doing your"Safety margin" calculations.

I also found some clear info on "cold inflation" and operation speed which was better than I expected. Tire life and expected replacement age were not uniform brand to brand but some of you may be surprised to see that some manufacturers actually tell you the number of years use you should expect from your tires.


Hope to meet a few of you at FMCA GLAMARAMA in Michigan in a couple weeks or in Gillette, Wy in July.   Safe travels.

New trailer sat for 5 years. Does it need new tires before a long trip?

Got this question:

"Good Afternoon Roger;  I have kind of a critical need for your expertise.  I've been a "Hardtopper" since 1970, and have always made every attempt to take good care of my travel trailers.  My latest and last, is a 2013 Flagstaff with of course dual axles.  I brought it home new after trading with a dealer, on August 31st, 2012.  Then the fun started !!  The tires are covered and are on wood planks, never having touched ground.  Rather than being able to realize a life-long dream of just once getting out of this horrible Winter climate, say to Florida for a season's stay, I was hit with the need for surgery and lengthy PT.  Each year since, I have been stricken with yet another number of surgery's for different reasons, and this past December fell on the ice at my home, breaking 3 ribs, thus cancelling once again, any hopes and dreams.  Now, after all that drama, I wonder if you might offer some "practical" advice on my tires.  I am a long ways from a rich man, barely getting by on my Social Security, so I'd really hate to have to replace the tires sitting unused as they have been after five years BUT, I would defer to your advisory.  I have read posts on RVTRavel.com and others have posted any number of articles in the past on tires, so I am a bit apprehensive, and sure to heck would appreciate your input.  Many Thanks in advance,  Grant M."

My reply:

"Sorry to hear about your situation, Grant. Your tires may be 2012 or even 2011 vintage (you can check the last 4 numbers of the DOT serial to confirm) but either way that's pretty old. How often did you check the air pressure? It should have been every month.  While they are covered and on boards, which is good, they were still under load without ever moving, which is bad, especially if they ever lost more than 5 to 10 psi.

If they are Radials there is a chance the steel belts may have lost some adhesion to the rubber due to moisture never being driven out of the tires with the warmth of being run down the road.

I would suggest you sell the tires to someone who has a utility trailer that only travels locally. If they have very little wear, you should get a reasonable price for them. You didn't say where you live but if you are thinking of travel from "North" to Florida I would recommend against the trip with a trailer that has just been sitting for 5 years. As a minimum you need to have bearings and brakes checked and yes, I am afraid new tires. You are just pushing the odds of having problems on the road that would be much more expensive to fix on the trip than confirming they are all OK before the trip.

Here are some of my posts on tire AGE from my RV Tire blog you might want to review."

Good luck.

##RVT804

When should you replace your tires?

Saw the following question on an RV forum from a motorhome owner.
"Does anyone ever just replace their front tires after 7 years? It seems that a tire failure on the front is much worse than the back. If the tires have a lot of tread and no sign of cracking, why replace the back ones?"

One reply correctly said, "There's more to consider than age. Were they properly inflated? Did you bang into curbs to damage the sidewalls? There are many failures due to improper operating conditions. Not just age."

I would first ask if you know the "life experience" of the tires:

Did the RV have a previous owner?
While they may claim they always checked inflation, can we be 100% certain?
Did you purchase the tires direct from a major tire company and know the complete use history?
Have you confirmed your load on all the tires from day one?
Did you ever discover one of your tires 20 or 30 psi low one time?

There are many things to consider, but if you are confident the tires have always been properly inflated for the actual load the following should help.

"Blowouts" (look at the picture at the top of my page), or more properly Run Low Sidewall Flex failures, happen because of running on low inflation. This can be avoided with the use of TPMS.

Belt separations, which are much less common on commercial grade tires, may occur after the rubber at the belt edges degrades due to cumulative damage from heat.

UV does not affect the internal structure of tires and external cracking is only one symptom of exposure to sunlight. I consider external cracking like having a person run a temperature. Having a temperature is just a symptom of some other illness, usually an infection. You can be seriously ill but not be running a temperature. Think of heart disease or cancer as two things that can kill you but don't cause you to run a temperature.

The suggestion on when to replace tires is only based on probability, as it is impossible to know just how much damage has been done to the components of a tire. The general suggestion is to have tires closely examined by a tire expert at 5 years and each year after that. Tires should be replaced at 10 years no matter what is visible on the surface of a tire.

I wrote a blog post on a suggested inspection and "step replacement" concept. A version of this suggestion could result in your keeping newer tires on the front, which in theory should improve your chances of not having a belt separation on the front. Of course also running TPMS will improve your chances of not having a Run Low Flex Failure too.

##RVT803

How old is too old part 2

Last week I addressed the topic of tire age. Some are still asking why there isn't a better and clearer age limit on tires in RV use. It may help if there is a better understanding of the complexities of what is involved in making the prediction.


I think that most can understand that the numerous variables involved such as ambient temperature, operating temperature, load, and operating speed all can affect the "life" of a tire. Also there is the obvious variation in the numerous components and assembly practice of each tire itself. All of this adds up to an impossibly complex equation if trying to predict the life of a tire.

While many may understand that if a tire spends its life in Arizona, Texas, Alabama, Louisiana or Florida, it will have a definitely different life span than one that spends its life in New England, even if the load, inflation and speed were magically identical. I do wonder how many have even a passing understanding of the complex nature of manufacturing a tire as seen in THIS animated video. Actual shots of the process are here.  Here is an alternate view of the truck tire process, which would be essentially identical to what is seen in both LT and 22.5" size tires. If you watch only one video, IMO this 3rd one is the best and most informative.

Unlike materials like steel or aluminum, rubber is not a homogeneous material so even minor variations in the raw materials can affect raw material properties and ultimately tire life.

Here is a video showing the basic process of preparing rubber before it is applied to steel or polyester cords. Note these are videos of very low tech methods. Modern equipment is much larger and the process is harder to see as there is much more automation behind closed chamber shields.

The estimates of maximum tire life are based on assumptions of the variability of the tire and the variability of the use of the tire. The estimate must also consider the probability of the variables stacking up and the potential for the severity of the tire failure.

Some companies may feel that no greater than 0.5% probability of failure at 7 years is acceptable IF the tire is always operated in North America, never exceeds its max speed rating or is overloaded for the inflation in the tire. Another company may feel that less than 5% at 12 years is the goal.

It is also important to remember that only after thousands of tires have completed years of service can a company know if it made the correct calculations. I do not know of any company that is not constantly working to lower the failure rate or extend the usage time while at the same time trying to meet customer demands for better wear, fuel economy, traction, ride and lower cost, and the order of priority for these and other variables the customer wants in their tires.

While compromising safety is never a consideration, the rank order of the dozens of performance characteristics can have an effect on tire life.

Here is a challenge with hypothetical information. Would all RV owners be happier if they were told that the maximum age of tires was 8 years   BUT it would be illegal to operate on a tire older than 8 years or operate without a load, temperature and pressure monitor and recording system "black box" system and tire warranty would only be good 4 of the 8 year life?  Oh ya, the "black box" monitor system would add $500 to the initial cost of the RV and there would be a required annual fee of $75?


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How old is too old?

Been following an RV forum thread on tire age and have been trying to explain why there is no strict guideline for exactly when a tire should be replaced. I summed up my position...


The general guidelines for motorhomes is to have the tire inspected starting at about 5 years and to replace at 10 years no matter what the inspection indicates. Due to the Interply Shear effects on belt durability, trailer tires need to be closely inspected after a couple of years and it appears that 5 years may be the max life for most applications.

I do understand that people would like a nice clear precise answer but the problem is that with load, speed and temperatures all having an impact on the life of a tire it is impossible to give a precise time of when to replace a tire.

In today's society no company can give a specific answer to the question as they would be sued if a tire failed before the "end of life" time and they would be sued if the tire lasted past the "end of life" time. We are talking about probability.

You have a sticker on your RV telling you the inflation to use based on an estimate of how much "stuff" you will be carrying. Federal Regulations say the tire load capacity at the specified inflation must be able to support the load rating of the axle. This assumes an exact 50/50 side-to-side load split all the time. It also assumes you do not put more or less load in your RV than what would result in each axle being exactly at GAWR. Many have learned of the importance of getting the actual load on each tire.

Maybe it would help if we thought about tread depth instead of age.

Exactly how much tread can be worn off before a tire becomes "unsafe'. Most states say 2/32" for passenger car tires but does that mean the tire with 3/32" tread will always perform equally to a tire with 10/32"?  Of course not. As the tread wears the wet traction capability goes down. Do you always wait till each tire gets to 2/32" before replacing it? If not, why not?

Conversely the dry traction can go up as tread depth goes down, so there is a trade-off. I dare say that if you live is an area with lots of rain or even snow, you probably change tires before they are that worn. However, if you live in the dry Southwest you may be tempted to run less than 2/32" tread as you have seldom if ever have wet traction problems.

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Help It's hot and I need tires

That's the message I read on an RV forum.
Here is the pertinent background info.

   "I am having a real issue with Michelin tires.  I live in Las Vegas and there are 3 tire companies that carry Michelin tires.  The problem is they all tell me they are back ordered and have been for awhile.  They have no idea when they will get any.  I have a 40' 2008 RV that came with Goodyear tires and have serviced us well.  I just don't know what do do since I can't get Michelin tires which seems to be the tire to get. Should I settle for Goodyears that are in stock?  My other issue is we are going on a trip next week that we can't get out of and because of the extreme heat here in Vegas we are afraid that our old tires might just fly apart. What should I do?"

IMO

While I can't address tire availability from Michelin, you need to remember that there are generally considered to be 3 tiers of tire companies. Michelin, Bridgestone & Goodyear as #1 with the tires made & sold by these companies as being essentially the same  ie Firestone & Dayton ~ Bridgestone, Kelly & Dunlop~ Goodyear and Goodrich & Uniroyal ~ Michelin.

Now there are some minor differences within a corporation but many times the rubber compounds and reinforcement materials are identical or very similar. Tread designs may be a bit more advances in the Corporate brand and the top of the line tires may not have an equivalent in the 2nd brand  but for most people you will not see a difference in performance.

#1 tier have their own tire stores with many hundred nationwide.

Now Tier #2 would be tires made by corporations that have their own tire plants. These would be companies like Toyo, Pirelli, and others seen on this list. They may not have any company stores and jsut depend on large tire distributors to market their tires.

3rd tire would be companies that are not on the list above. These may actually be just sales companies the have other companies make lower cost product for them as "private brand" , Sometimes the same tire is made for a number of importers with only a name-plate change in the mold to differentiate the "brand" These companies seldom have their own stores but sell their products through wholesalers.

Check the tire warranty and I think you can get a good feeling for the real quality of the tires you might be considering. Are there lots of exceptions or if the warranty short could be a tip off that the seller isn't real willing to stand behind the products they are selling



+++++++++++++++++++++++=
Now to your concern about your current tires and the hot temperature.  It's kind of hard offering an opinion or suggestion on if you need new tires right away or not, but tires simply do not fail simply because it is hot outside. Excess heat is not good for long term durability but if the tires have always been properly inflated, never been punctures or run even a few psi low you should be OK for a while.

You didn't offer your actual age of your tires but they are probably 7 to 8 years old. You also failed to provide info on how you store your tires. Inside or out in the Sun? Do you have a lot or a little extra load capacity based on actual individual tire position weights? Do you run a TPMS and have never run lower than what is needed to carry your actual measured load. All of these items can contribute to making a suggestion to change your tires right away or suggesting that you can wait a few weeks or months.

If concerned about road or ambient temperature just drop the speed down. Don't run 70 when 60 will still get you there. Last Aug I drove Ohio to Oregon at 60 - 62 with no problem.

Can you increase your tire pressure without exceeding the tire or wheel max?

Where are you headed?  Have you checked to see if there is a large tire dealer at a future location that has tires for your RV in stock?

UPDATE:
In the meantime I would suggest you go to a Goodyear truck tire dealer and have the tires inspected. Let them know your concern about the tire age and current hot temp in Vegas. Let them know your actual scale weights (Go to a local truck scale location first. There are a number around Vegas I'm sure)  and your normal cold inflation. WHile there ask if they would confirm the accuracy of your pressure gauge. If a stick type +/- 5 is about what I would expect. If digital (better) +/- 2 would be good. If outside these numbers you need a new gauge. Check my blog on tire gauges and how to have a reliable "Master Gauge" of your own for less than $15.
The tech should be familiar with the Goodyear tires you have so can offer first hand information on the condition of your tires.
Remember you can always get just the two fronts replaced as a failure there would be the greatest concern. With a TPM on the rear duals a failure would be less dramatic and you should get plenty of warning so you can safely pull over quickly before serious damage is done.

===========================
It would be nice to be able to offer more specific answer to his question but all to often people fail to provide important information that would allow more than a wild guess.


++++++++++++++++++++++++
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NEW DOT serial info but date code portion to stay the same

NHTSA Standardizes Tire Identification Number

Change Accomodates Increasing Number of Global Tire Plants

WASHINGTON, DC, April 14, 2015 – The National Highway Traffic Safety Administration (NHTSA) announced a final rule to standardize the Tire Identification Number (TIN) imprinted on tires sold in the U.S.  The new regulation creates a 13 digit TIN for new tires and seven digit TIN for retreaded truck tires.

NHTSA initiated the rulemaking because it had exhausted the number of two-digit plant codes the agency issues to every tire plant making tires for the U.S. market.  The new TIN will have a three-digit plant code.

The Rubber Manufacturers Association commented to NHTSA when its membership voiced concerns over some aspects of the proposed rule.

“RMA appreciates NHTSA’s effort to create an effective regulation to continue its obligation to provide plant codes to manufacturers while making common-sense accommodations to limit unnecessary costs,” said Dan Zielinski, RMA senior vice president, public affairs.

RMA commented on the proposed rule urging NHTSA to drop a proposed requirement for a 50 mm blank space after the TIN. RMA argued the additional space would add significant cost to the rulemaking with no safety benefit while causing extensive remodeling to tire molds around the world. The final rule eliminated the proposed 50 mm requirement.  Additionally, RMA successfully argued that tire manufacturers be given 10 years to phase in the new rule’s requirements.  RMA noted to NHTSA that a majority of tire molds last as long as 10 years. NHTSA agreed with RMA.

“RMA agrees that NHTSA needs to change the TIN to a three-digit plant code,” said Zielinski.  “RMA members had several concerns with the proposal that would have needlessly raised costs to tires produced in the U.S. and NHTSA agreed to make key changes.”

In response to other stakeholder requests to change the date stamp portion of the TIN, NHTSA said, “…we do not believe a change to the date code is necessary for consumers to determine when their tires were manufactured.”  NHTSA added that sufficient information to understand the date stamp is available online or by asking a tire dealer.”

Click here to link to NHTSA rule.

# # # #

The Rubber Manufacturers Association is the national trade association for tire manufacturers that produce tires in the U.S.  All RMA press releases are available at www.rma.org.

===========================
 I am confident that the info on the plant look-up web site http://www.harriger.com/tires.htm
will be updated as new plant locations are added.



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Soften the blow to your wallet when buying tires

Recently read a blog post about the "sticker shock" of the cost of "truck type" tires for the large RV. I would like to offer a suggestion on how to soften the financial hit. This strategy can work for all RVs be they trailers, Class-B, Class-C or Class-A size units.

It a simple plan and will only take a few minutes to lay-out. With the planning behind us we will be prepared to take advantage of any special deals or short term sales we might come across.

Now to follow this plan there are a few bits of  information you need to have:

You need to know the exact size, Load-Range and DOT serial date for your current tires.
Sorry but just thinking you have 235-16 size tires that you bought in 2009 doesn't cut the mustard.

If you are not sure how to get this information I suggest a quick refresher is in order so you might read the post on "Reading a Tire". So lets assume you have collected the details on your tires so you know exactly what you will be looking for over the next few months.

Here is how my suggestion works.
If all your tires are the same size I would suggest you plan on replacing the two oldest tires first. The new tires would go on the front positions and the others in dual position in the back.

Next year I would buy two more new tires, place them on the front and move the tires that were on the front back to one pair of duals.

Then the third year buy two more tires, place them on the front position and move the older fronts back to the rear.

The above schedule serves a few purposes:

1. It spreads out the purchase over a three year period.
2. It has you running on the newest tires on your front position.
3. With this plan you can spend months shopping for the best deal and avoids the need to accept tires that may be years old before you even buy them. Since you know you have a plan and you know that over a six to 10 month time period to do your shopping.
4. When you are done you know your oldest tires are three years old and if you plan on changing tires when they get to seven or eight years you now have a four year period to set aside some cash for when you start the cycle over again. You can continue this schedule for as long as you own your RV and never be confronted with having to buy more than two tires in any year.


Now if your fronts are different size than your rears as seen on some large Class-A units you can't do the front tire rotation but you can still limit the purchase of your rears to just two a year

With a little planning no one should have to buy more than two tires in any one year. It just takes some thought and planning.



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DOT Date Code - Why do they make it hard to find and read?

How old are your tires? 

How do you learn the answer?

What is the DOT date code and why is it so hard to find and read?

Answers to these and other important quests can be found right here at RVTireSafety.com.


DOT regulations (Law) specify the size of the serial ( 1/4" min) and parts of the content as well as placement (below the midpoint of the sidewall).

The first two characters are a "Plant Code" which as far as I know is standard as I have never seen a variation from the industry code list.

Characters #3 & 4 are not uniform across all tire companies but would be uniform within a tire company and these are a code for the tire size. Sorry but I have never seen a list for all tire size codes for all tire companies. In reality you don't need to know how to "translate" the code as you simply read the size off the tire sidewall.

The next series are optional. These may be used by different tire companies for internal coding. Some companies us no code others may use 1, 2, 3 or 4 characters.

The last four NUMBERS  are the date code, with the first two numbers being the week number starting with 01 and ending at 53 ( The code is changed on Sunday and some years have 52 and some have 53 Sundays. Bet you didn't think of that.) The last two are the last two characters of the year.
Prior to May 2000 the year portion was just a single number but since you should not have tires older than TEN years on your RV you better not have a tire with just  three digits!
The year part changed in 2000 as before that only the last number of the year was used along with another symbol but it was decided in late 1990's that this was too complex so the switch from three to four numbers for the date code.

Since the date code MUST by law, be changed each week this presents some challenges to the manufacture of tires as a person has to do this change. This presents safety issues as reaching the top part of the mold would require a person to climb into the cure press which is HOT (250° to 350°F) and the equipment could accidentally close on the person, so only the bottom side of the mold gets the date portion of the code.

Some car companies have a practice of placing the side of the tire with the full code on the outside but with dual application this means that for RVs the rear tires will have to be different than the front or the date code would be facing the tire that is its mate and very difficult or impossible to read without dismounting the tires from the RV so RV companies do not have this requirement.
This is one reason why whenever buying new tires you should ask for the full DOT serial to be recorded by the dealer on your invoice and that information be stored along with other important papers and information you keep available for future use.

 Here is some information from earlier posts on the DOT serial. If you want to read more just search using the Label list on the left side of this blog.
The DOT Serial

This has important information used in determining the tire age. Other information such as the location of the tire plant that made the tire is part of this code ( first two characters  8X in this example). If there is a recall, this code is used to identify which tires are covered by the recall. NOTE that the last portion, the 4 digit date code, 3908 in this example is only molded on one side of most tires. Every tire sold for use on the highway in the USA must have a full DOT serial including the date code molded on at least one side. This tire was made the 39th week of 2008.

 

 Do not confuse the fact that the 6E7378 ends with four numbers as there is no 73rd week of the year 2078.

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How do I inspect my tires?

Got an email the other day asking about inspecting tires. This blog and many others will tell you that you should do a thorough inspection annually and doing the inspection becomes more important as times goes on.

The problem is, few know even the basics of proper tire inspection. For some it's only looking at the tread to be sure there is some tread pattern available. Others will bend at the waist and look at one sidewall to inspect for large cracks.

Well, sorry to say that doing a proper tire inspection is a lot more involved. You will need to get down on the ground, you will get your hands dirty and you will need a good bright work light. A dim, old style flash light doesn't provide either enough light or uniform lighting to allow a good visual examination. So lets start with the tools you will need. I suggest a rug or old blanket so you can lay down and even scoot part way under your RV to see the back side of the tire. For lighting a work light with at least 75 watt rating. As a low cost alternative if you don't already have a work light is the inexpensive LED light similar to THIS one or even THIS one. Note the low costs for these lights. A pair of thin gloves. You need to be able to feel bumps and bulges on the tire so thick leather work gloves like these

 will not do.I know that many have disposable thin, Latex or Nitrile gloves they use when handling their holding tank hose and that type or similar will work fine to help keeping your hands cleaner as tires are very dirty and rubbing your fingers across the sidewall will transfer oils, waxes, dust and dirt to your fingers.
Finally don't forget safety glasses. Dirt can drop from under the RV onto your face or when you are removing objects from the tread they can pop out and hit you.

We need to be consistent and thorough in our inspection as we need to cover 100% of both sidewalls and 100% of the tread. This also means that after you have inspected all your tires you will need to move the RV a couple of feet so the portion of the tread that was on the ground can be seen. Depending on your RV, there may also be areas on the inside sidewall where the tire is too close to the frame or other component which prevents a clear view of that part of the tire and this may require a couple of small moves. When going under your RV be sure the engine is off, the transmission is in Park and you have blocked the wheels from moving either direction.

The following applies to all tires. If you have a towable there are some extra steps you NEED to do and we will cover them later.

On to the INSPECTION


1. Tread. You are looking for nails, screws and other items lodged in the tire. Sometimes you will find rocks wedged in parts of the tread pattern. It doesn't hurt to remove them using a screwdriver as sometimes stones can "drill" into a tire causing damage. I would not use a knife or other sharp tool. If you find a nail or screw in the tread, it is possible that the object goes all they way into the air chamber and if removed may cause an air loss. If for example you find a screw you might start to remove it but if you get more than 1/4 to 1/2" loose and the screw is still in the tire I would screw it back in and seek service as you don't want to lose air by completely removing the screw if you are not a a location where your tire can be easily be changed. Making this decision takes some thought to avoid making the problem worse.
While looking at the tread see if the pattern looks uniformly worn both across the tread and around the tire. Non-uniform wear may be a sign of an alignment issue and in some cases are an early sign of a structural problem internal to the tire like THIS,

or it may not be serious and is just cosmetic.

If you see some localized wear and want it looked at by a tire dealer it helps if you make a notation using the letters and numbers on the sidewall for reference. An example might be "Local wear on Right Front, inside shoulder of tread, starting at number 3 clockwise to letter G".  Giving a dealer this guidance will do two things. One it will save them time in locating the area of concern and two it will let them know you have done a thorough job of inspecting tires so they are less likely to ignore you and more likely to treat you as a knowledgeable customer that knows something about tires. This is a lot better than telling the dealer "The tread on the front tire looks strange".
While we are still looking at the tread we also want to note for more detailed inspection  any cuts that are deeper than 1/16" in the grooves.

2. Sidewalls:  This applies to both inner and outer sidewall. First do a general inspection for cuts or punctures. Punctures in the edge of the tread and down to the wheel should NOT BE REPAIRED. Some people may claim to have done a satisfactory sidewall repair but there is just too much flexing for a repair to last. There are published GUIDES that show the only location (in the tread) where a repair is acceptable. This applies to ALL BRANDS of tires.  Any cut where the body cord is visible means the tire is scrap and should not be used. Next we want to find bulges. You want to feel for bumps and bulges using your fingertips and gently slide around the complete surface of both sidewalls of the tire. If the frame prevents this then you need to identify where you could not feel the sidewall so you can finish that part of the sidewall after moving the RV. Bulges can be a sign of broken body cord. I recently did a POST on broken body cord on one of my personal tires.
Depressions however are probably OK as for tires with multiple ply such as most LT and ST type tires this is just a small overlap where extra material is located. if in question just note the location as mentioned above
and ask a dealer to confirm.

Trailers: Tires on towables seem to have a much shorter life than tires on motorized RVs like Class-A, B or C. Part of the reason for this is the unique and higher structural loading placed on these tires during any turning. The sharper the turn the higher the stress is on the tire ply. This loading is working to tear the tire apart. These forces can lead to separations which ultimately can lead to tread and belts being thrown off the
carcass and in extreme cases a rapid loss of air when the belt separates. TPMS will not provide warning of a tread separation so the only tool available to RV owners is a thorough visual inspection.

The good news is that many times these separations can be discovered by doing a "free spin" inspection as seen in THIS video. At the beginning, you see that the wheel is round and shows no side to side movement. Then we see the tire as it wobbles side to side and even is out of round. This tire has failed and must be replaced at once. Here you can see when I did an "autopsy"

we discovered the belts are almost completely separated on this tire. To do a "free spin" you must get the tire up in the air so it rotates freely. Thus can be done with a jack or even one of the ramps that will raise one side of the trailer high enough as seen in THIS video. This is just one example.
As you can see there is some work involved but doing a thorough inspection may prevent serious problems later on down the road. You will also find that after doing a few tires you will become more knowledgeable about this important safety item on your RV. your tires.

NOTE Repair Guide link fixed 7/5/2019

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Are my tires too old?

 How old is too old ?  The guy may have a lot of "life experience" and be older than the normal rider, but can you say with certainty he is too old to be riding a bike?

After reading my posts on the benefit of using white tire covers, a reader noted my comment on having tires that were 7 years old on my coach. He thought I was not practicing good preventive maintenance as he had heard that all RV tires should be replaced by 6 years "no matter what".

I offered that the recommendation on the max age of a tire on an RV is not as clear cut as some would believe.

According to this RV tire guide from Michelin they recommend annual tire inspection by a qualified tire dealer after 5 years but replace at 10.

I have seen posts such as this on RV forums " The Michelin RV Tire Guide specifically says  that  tires may be good for  up to 10 years, but  recommends that they should be thoroughly inspected annually, especially after five years.  This same information is summarized in the Michelin TSB on Service Life for RV Tires:
The Michelin Truck & RV Tire Warranty is for the life of the original tread, not a fixed number of years, and starts on the purchase date .Sidewall date is used only if you have no sales invoice.
Note, however, that passenger and light truck tires may have different parameters. If your motorhome uses 16" tires, I would apply the passenger & light truck recommendations.
That said, I will continue to replace my tires at the seven year mark. Far too much risk of a blow out beyond that point.  The risk of body damage or accident is just too great for me."

Now I have not been able to confirm every statement about tire life that people post on different forums. The above examples are from Michelin and are about tires on cars, trucks and motorhomes. There are those that say for RV trailer application 3 to 5 years is a maximum.

Here is a good editorial from a trade publication on the topic

Clearly there is no simple answer. As a tire engineer I can tell you that there are just too many variables that would need to be considered before a simple xx months max type answer can be provided.

Some variables would include time spent exposed to direct sunlight, time spent at temperatures above 80F, 100F,  120F, 140F or above. How much reserve load capacity (Load capability minus actual load)  for each tire. Amount of time spent at or below the minimum inflation needed to carry the actual tire load.

My tires have been in service since April 2008. I run 15 psi above what is needed for the actual individual tire load and the tires have never been lower than 8psi above the minimum inflation needed. The tires are always covered if I am parked for more than a day. I have not traveled where the temperature exceeded ever exceeded 90F. By training and experience I am a Forensic Tire Inspection Specialist so am fully qualified to do internal and external tire inspections.

I will be replacing my two front tires next Spring and two additional tires each year there after.  BUT this does not mean you should not be replacing your tires when they are less than 10 or 8 or even 5 years as the "life experience" of your tires is different.

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WATCH A VIDEO: How your RV tires can "age out" before they wear out.

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UV Tire protection. The FACTS

For some time I have been reading posts and advertisements about tire covers and UV protection. As an engineer I prefer FACTS over sales PR.

This investigation has taken more time than I originally wanted as I needed a reasonable way to measure UV and a day with full Sun.
 - Not something easy to find in NE Ohio-

As they say it all came together today April 16 2014. While it was cold 24°F last night and we had an inch of snow yesterday, it is bright and sunny today with only a little haze in the sky.

The test uses a Hawk2 UV meter. This unit is intended to help you judge how much sun you are getting while at the beach but I felt it would serve my purposes as we are not trying to measure an absolute value in milliwatts per square centimeter but a gross relative level of shielding of different materials used to cover tires.
If interested you can learn more about UV HERE and more about the UV Index HERE

I set up a test using my RV.

As you can see the UV of 6 years here in Ohio,  has pretty much destroyed the cheap vinyl used by Coachmen for the side decoration. Anyway the front tire has my normal white vinyl tire cover and there is a standard blue tarp, a roll of window screen and some black cloth backed vinyl similar to what is used in black tire covers.

I will show the meter readings for each "shield".
Full Sun gives a reading of 9 which is considered "HIGH"

 while in full shade the reading in zero.

Under the white cover the reading is zero

 and even under the black cover the reading is zero

.

  but the screen only reduced the UVI to level 5

I interpret these results to indicate that anything that is not in direct sun or that shields all direct sunlight will provide adequate protection from UV damage for tires.

I would not be worried about reflected light going under the RV to the back side of the tires as this is full shade. After all, tires are designed to be outdoors and we are not trying to protect tires for 20 years but only to get past a normal vehicle usage of 4 to 5 years to the 8 to 10 year range for many RVs. I would not consider open mesh as used in some "tire covers" complete protection but it is probably better than nothing.

NOTE I did not address the effects of heat on tires in this post. I did cover in THIS post and that clearly shows that white covers are the ones to use if you want to keep your tires cooler so they age more slowly.

BOTTOM LINE
If you want to protect your tires to give you the longest life possible you need to cover them with white solid covers such as cloth backed vinyl being a most reasonable option.

Tire Warranties

Recently saw a post where someone stated emphatically, and incorrectly, that tire company ABC only covered their tires from date of a manufacture. So in an effort to set the record straight I decided to pull together some information. I am providing links and only a brief summary of the length of time a tire may be covered. As you see the time does vary and in many cases the clock doesn't start ticking until the date of sale BUT you will need to keep your proof or purchase.

You may recall that in my post on The Best Tire, I suggested that one measure is the warranty.

I strongly suggest you read the warranty information for your brand and type of tire. In some cases the coverage for a Light Truck Radial, LTR is different than a Truck Bus Radial, TBR. DO NOT use what I say here as the final say or as the complete statement of warranty.



In alphabetical order...

Bridgestone  TBR
"WHAT IS WARRANTED and FOR HOW LONG
Upon examination by Bridgestone, before wearing down to 2/32 inch (1.6 mm) remaining original tread depth (i.e. worn down to the top of the built-in indicators in the original tread grooves) and within six years (seven years for certain tires, see the section entitled “Enhanced Casing Limited Warranty”) from the date of tire manufacture, any eligible tire that becomes unusable for any reason (see exclusions in the section entitled What This Limited Warranty Does Not Cover”) within the manufacturer’s control will either be repaired or replaced with an equivalent new Bridgestone brand truck tire on the basis set forth in this Limited Warranty. occurs first. At that time, all warranties, expressed or implied, expire."

Bridgestone LTR
"5 years from the date of purchase—proof of purchase date required, or (b) 6 years from the date of tire manufacture without proof of purchase date"


Cooper LTR
"Worn to 2/32” (1.6mm) or more than 72 months old (based on date of purchase) whichever comes first. Proof of  purchase is required. Without proof of purchase the manufacturer date will be used to determine eligibility."


Firestone  TBR
"What This Warranty Covers And For How Long
If before wearing down to 2/32nds of an inch of original tread depth (i.e., worn down to the top of the built-in indicators in the tread grooves) or 6-years from the date of manufacture (referenced by the last three or four digits of the DOT number), whichever occurs first, an examination by Firestone shows that any tire covered by this warranty has become unusable for any reason within the manufacturer’s control, such tire will either be repaired at no charge or replaced with an equivalent new Firestone tire on the basis set forth below...."

Firestone LTR
"3 years from the date of purchase – proof of purchase date required, or (b) 4 years from the date of tire manufacture without proof of purchase date. "


Goodwear TBR RV service
"The new tire coverage of this warranty ends when the treadwear indicators become visible or five (5) years from the date of purchase, whichever occurs first. The only exception is weather cracking, which carries a seven (7) year warranty from the date of purchase or when the treadwear indicators become visible, whichever occurs first. Without proof of purchase, date of manufacture will be used to determine eligibility."

Goodyear LTR
"6 years from the date of original tire manufacture, or new tire purchase date (whichever comes first). (Without proof of  purchase, the date of manufacture will be used to determine eligibility.) "


Michelin  TBR
"MICHELIN® truck tires bearing the MICHELIN® name and complete serial and identification numbers, used in consumer service, such as on a motorhome, according to the instructions contained in this Operator’s Manual, are covered by this limited warranty against defects in workmanship and materials for the life of the original tread or five years from the date of purchase, whichever comes first"

Michelin LTR
"If there is a defect in workmanship and materials during the life of the original usable tread, or six years from date of purchase (whichever comes first), a replacement"

Toyo Truck Tires
• Within the first 2/32nds inch of tread wear
• Used in the service it was designed
• Within 66 months from the date of manufacture



Bottom Line
I provided some links. Use them and read the contract. It is your responsibility to get clarification from your tire dealer.

DOT Date Serial

Sometimes I am just too close to a subject and I have to step back and remember that most people have little or no training in tires.

I just read a post where someone claimed to have read the tire date code and interpreted the code as indicating the tire was five years old when in reality the tire was 15 years old.

Now I know there and been a number of posts telling people how to read the date code but clearly there is still some confusion. So I did a quick search for pictures I could find  of actual date codes.

First off we need to remember than in 2000 the DOT serial date code changed from a three digit date code to a four digit date code. The DOT serial is a series of letters and numbers that come after the symbol DOT on the sidewall of your tires. Also the complete serial that includes the date code portion is not normally on both sides so you may need to do some crawling around. You might even get your son or daughter or even your grandkids to help.

You can also look at passenger tires to get some practice. I know a number of companies mount the tires with the full DOT serial on the outside so it is easier to read but I do not know of any RV manufacturer that has an official policy of making the full serial be on the outside.

So lets look at some examples.
This first example shows the 3rd week of 2001 and we also know the plant code is W2

 This example has 39th week of 2008 with the manufacturing code of 8x

 This example on the left is 41st week of 1994 or possibly 41st week of 1984. This is a good example of why the date code was changed to four digits.
















and below we have an example of 37th week 1998 on the left and 7th week 2009 on the right.

 

 Do not confuse the fact that the 6E7378 ends with four numbers as there is no 73rd week of the year 2078.

If you want to look up the location of the plant that actually made your tires you can go to THIS web page.

Hope this helps clear up any confusion.