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Tuesday, March 10, 2015

New Speed info for trailer tires

Learned about some interesting new developments that involve speed limit ratings for ST type tires as used on a majority of RV trailers.

On Nov 24 and updated Dec 30 the US Dept of Commerce issued preliminary guidelines as they pertain to imported tires. This involves what are called "countervailing duties" (CVD) These anti-subsidy duties, are trade import duties imposed under World Trade Organization (WTO) rules to neutralize the negative effects of subsidies from foreign governments that benefit the production of goods from foreign companies.

Now without going into all the legal details this means that some import tires will have a fee added to their price unless they receive an exemption. The fee can be in the 12 to 81% range, so these are meaningful.

This new fee will apply to P and LT type tires primarily made in China. ST type tires will receive an exemption but in addition to the ST as part of their size designation the tires must have either
“For Trailer Service Only” or “For Trailer Use Only” molded on the tire sidewall.

Now the Nov statement indicated that ST type tires must also have a Max Speed in MPH or a Speed Symbol letter also molded on the tires. I thought this was great news as it would then become obvious to RV owners that they needed to limit their towing speed.

However the Dec "clarification" excluded the speed limit requirement.


I have also learned that a few tire importers have gone ahead and will probably be marking their ST type tires with either "Max Speed xx MPH" or with the Speed Rating letter symbol. The information I have is that the symbol would probably be "M" (81 MPH)  or possibly an "N" (87 MPH) and that tires might be available by early this Summer with these speed ratings.

Of course if a tire company is moving from a tire rated for 65 mph as current ST type tires are, to a higher speed they will need to make some changes in the actual tire construction.

While the final rule has not been published, I wanted to let people know that there may be some short term confusion as both tires, literature and web pages need to be updated to reflect what the tire capabilities really are.

In my opinion the information actually on the tire takes presidence. So unless you can get something in writing about your specific set of tires that states otherwise, the lowest speed you find on your tires is what your tires are rated for. For normal ST type tires this means 65 mph Max even if the number is not on your tires..  Not occasionally but ever.

I will publish an update when I learn more.

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  1. I believe that Uhaul has had it right for years. 55 MPH and that is where I drive my 26 foot travel trailer never more than 60 MPH. First of all, what's the hurry and secondly, why put your equipment through hell trying to get where you want to go.

  2. Ken, I am not advocating that people drive faster. What I am trying to do is to address the question of people traveling at speeds faster than the tire is rated for


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