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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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