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Thursday, August 25, 2016

Why aren't there more recalls of bad RV tires?

In addition to writing this blog, I monitor a number of different RV forums for discussions on tires and related issues. I find that many times I am suggesting to people that they should file a complaint with National Highway Traffic Safety Administration about their tire problems. Many times I get replies asking "Why Bother". While this post focuses on trailer tires the information also applies to other RV applications.

"I get tired of hearing that most ST tire problems are caused by the RV owner. I simply don't believe it based on my own experience. NHTSA; never heard of them, much less knew I could file a complaint. So I asked my tire dealer. She said that they do turn in reports on tire problems themselves and/or turn the tires over to their tire reps for analysis. That went for tires they sold or other brands they replaced. So I don't believe the argument that NHTSA doesn't have enough data to see a trend for ST China bombs. Doesn't make sense if tire dealers are turning in info to them to protect their sales and customers."
Scott I have a number of posts on NHTSA. Here is my take on recalls and filing complaints.

They have a limited budget so must focus on most important first. That means things that can result in death or personal injury. TT only see financial loss so obviously would come last.

While your dealer may have sent information to the tire importer I have noted that many times the volume of tires in a "family" may be low enough to avoid the requirement for data be sent to NHTSA.

in 2014 207 Million passenger tires were sold, 29 Mil LT 18 Mil Truck or 254 Mil tires sold each year where a failure might result in personal injury

According to RVIA data there are 9 Mil RVs on the road but this includes approx 1.1 mil motorhomes so if we have 7.9 mil trailers with say 90% on ST type tires buying a set of 4 tires once every 4 years we are looking at maybe 7 mil St type tires sold each year

So if you were NHTSA where would you spend your research tax dollars? On the quality of 254 Mil tires where there might be injury or on the quality of 7 mil tires with almost no chance of injury?

There have been a few recalls on ST type tires but I am also aware of times when ST tires are not recalled simply because the records are poor as most are imports. In some cases the importer is a small company so does not have the money to do a recall that can cost many million dollars even for a small recall. IMO sometimes a small company would simply go out of business rather than try and handle a large recall.

The RV owners seldom file complaints and many times when they do they do not include the DOT serial so that complaint can not be used in the tally of number of complaints.

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Here is a reply to another reader:

Tireman, this seems to me to be a big picture economics issue. Is it true that the auto and truck industry does not experience the failure rate or short life that the ST tires experience? If true then the RV tire industry and rv chassis mfgs apparently are not willing to manufacture to the same expectations of the auto industry leading to all the woes that we experience. Look in any parking lot and many of the cars are running on poorly inflated tires. My guess is that these do not fail at the same rate as ST tires. I also have an engineering/QA background and have abused tires for 50 years in racing, towing and with heavy Ag equipment and never seen the failure issues we see with ST tires. I do properly maintain and store my tires, even so I have had 3 failures out of 8 tires in the last three years. Anecdotally I also travel enough to see too many RV trailers on the side of the road with failures. If not for economics, why would ST tires only be made to be rated at 65 mph when we live in a faster world? I try to stay under this for fuel economy but find myself at higher speeds frequently. Impossible to practically operate within rated limits. Is this whole issue because RV mfg do not want to pass on the cost of safe tires? I understand Motorhome tire life is 5 to 7 years and tractor trailer operators get hundreds of thousands of miles on tires. ST tires 2 years? Please explain.

IMO the main reason RV TT mfg do not provide better tire fitment (load capacity) is they sell based on "Bling at low cost". When shopping the RV market you will almost never meet a salesperson who tries to sell based on specifications. Yes tires applied to TT are designed to meet 1970 driving speeds (55 mph speed limit) IMO RV Industry lobby actively opposes any change in requirements that might increase costs by even a few dollars.
Yes ST tire life is MUCH shorter than Passenger, LT or Truck tires.

Universal use of TPMS starting in 2005 on passenger cars has significantly lowered tire failure rates on cars but RVIA (mfg association) does not support TPMS as OE on RVs is one example. They also do not support applying 2002 DOT test requirements on ST type tires so you are stuck with 1970 performance in the 2016 world.

You could write to RVIA at info@GoRVing.com but I have been told that as an industry representative organization they may not be very interested in individual complaints.

If you want to learn more, read some of my posts about NHTSA.

PS While I have done training at NHTSA in Washington DC I do not work for DOT or any Gov agency.

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Tuesday, August 2, 2016

Can you "contain" a tire failure ?

I read a story about someone that had a couple of tire failures on their trailer. He was trying to build a solid steel shield over the tires in the wheel well in an attempt to contain the "Exploding " tire.. I offered a reply...

Sorry, but IMO trying to "build a shield" just is not a reasonable approach. I doubt that you can spare the 500 or more pounds of steel it would take for the shield and structure to support the shield. Since a failure of a tire can be explosive event a solid wall will not let the force dissipate. You need an open grate. Check out this compilation of exploding tires to see the forces involved. Note that most of these did not involve a tire spinning at 50 to 65 mph which would add significant force to any explosion.

You need to remember that tires simply do not fail catastrophically without some reason. There is no magic involved.

Starting with a new tire...
1. It can fail in the sidewall if it is run at highway speeds (30+) while significantly under-inflated ( 40 to 80% low). Polyester melts. Steel tires do not need the speed but steel fatigues so after maybe a couple thousand cycles you get a "zipper" failure. Properly functioning TPMS can warn of the air loss in the first couple seconds of a loss ( of just a few psi for some brands). In most cases this early warning will come way before the tire has lost enough air to result in steel fatigue or body cord melting. If you have a TPMS have you tested it? Can you hear the buzzer over the loud radio?

2. Radials can have a belt/tread separation. This takes many hundreds or even thousands of miles to grow large enough for the tire to come apart. This is where the close inspection in my blog post comes in. As I showed a tire with even significant separation does not have to come apart at once but it does leave visible clues.

The reason for belt separation is a combination of initial tire design and material selection and the long term use. Initial design can not prevent all damage done through excess heat and age but current technology in first class radials should deliver 5-6 years or 30 to 60,000 miles at specified inflation and a max of 80% load, except for multi axle trailers.

Due to trailer suspension design there are unique forces "Interply Shear" placed on TT tires that result is about 24% higher shear forces than seen in motorized vehicles. This means you would need to run very much decreased load ( maybe -25% to -50%) to get the same life on a TT application than the same tire on a TV application.

I do not know of any direct comparison real life testing so can only guess at the above figures other than the 24% that comes from Finite Element computer simulation that is a well developed tool in automotive circles  other than the RV industry.

Rubber strength degrades with time and heat with HEAT being an over-riding contributor. Do you cover your tires with white covers? This can result is a very significant lowering of tire temperature. Every hour of full sun exposure can be equivalent to two to 3 hours of use running down the highway at top speed.

Quick example: 8 hours a day 7 days a week for two months each summer can be the equivalent of 10,000 miles use as far as rubber degradation is concerned. So if we assume a tire is good for 40,000 miles  and you park it as in the above example after 3 years you may have "consumed the equivalent of 30.000 mile tire life, just while parked.

IMO making some effort to prevent a failure in the first place (TPMS & frequent inspection) would be a better use of time and money than trying to prevent damage to the RV with some sort of shield. 

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