Truck tires on tt?

tomman58 wrote:
Truck tires and trailer tires are two different animals. The truck ones are not as strong in the sidewalls and the general method of building is different.
The main problem with having a trailer just sit is they rot out from the inside as the need to move to lube the inside.

Since it is the air pressure that carries the load and not the tire sidewall, I really do not understand the "stronger sidewall" argument.

If you look at an ST type and LT type tire of same dimensions and Load Range you will see they are both rated for the same inflation.
Now the ST is rated to carry more load but that is primarily due to their max speed rating of 65 which means you need to drive in the 50 - 60 mph range and only see 65 for very short times (couple of minutes) when passing and never anything above 65.
LT tires can handle highway speeds.

LuckeyUs wrote:
We live in Florida & the summer heat destroys our tt tires. We keep them covered & don't drive over 65 mph, and yet, we blow tires every 2 years. We were advised by another RVer to use truck tires on the tt. Has anyone done this or do you have any recommendations?

It sure would help if we know your tire size, load range, measured tire loads (individual or at least by axle)

"Blowouts" are usually run low flex failures that are the result of running more than 85% of the load capacity of the tire based on its cold inflation and actual individual tire loads and/or having a puncture, cut, leaking valve or valve core or wheel.

TPMS can provide sufficient warning to allow you to pull over before you have damaged the RV and sometimes even before the tire has been turned into scrap.

I've stated before and will do it once more. I put about 10,000 miles on the TT each years and have seen tires wear from excessive turning from the mountains to the cities.
I am a firm believer in ...... if you don't use it you'll lose it. This applies to tires especially, if you let them just sit around and occasionally go somewhere once or twice a year, you will not do your tires any favors.

My point is that whether you pick an LT tire or an ST tire may be the lesser issue. There needs to be a significant margin between static load and tire load rating to stay safe when towing. Manufacturer's recommendations don't achieve this on the trailers that I've examined. Whether LT or ST, you need to go up a couple of notches in load rating from the factory installed tires to make sure they're not overloaded when underway.

Other parts of the suspension are also at risk, but this can be discussed some other day.

One more time,

Yes LT tires undergo far more rigorous testing than STs, if you want to believe that those tests are all inclusive, that is fine.

I believe if that were the case, then the tire companies would not have wasted their time creating an ST tire with stiffer side walls, a rolling not traction tread design, unique rubber compounds etc. That is their words not mine. It is a purpose built tire for a specific application, trailer usage.

I suspect that an Indy racing slick tire undergoes far more rigorous testing than an ST but I would not want to use it on my TT.

My choice it to use what the tire makers designed for trailer service, others are free to make their own decisions. Certainly in the last 9 pages all sides of the issue have been discussed and rehashed. At this point any more dialogue would be anticlimactic.

Take care and you folk have a good day.

This poster is still here.

I'm really ticked off at the RV industry.
This problem is real, pervasive, commonly ignored, but explains a lot about the prevalence of unexplained tire failures on trailers.
We're all put at risk of having a tire failure as a result.
Mine occurred at a really bad location (Monarch Pass) where I could easily have driven over the cliff at the side of the road.

Grumble.

Men, I'm just gonna have to bug out on this discussion, because at this point I can't tell whether I should follow the advice of the tire company, the trailer company, the tire engineers, or a guy that has multiple advanced degrees from MIT ( this poster seems to have disappeared ?? ). :) ;)

I think I'll just keep doing what I'm already doing regarding tires.

"The tire engineers here on the forum tell us that "the dynamic forces involved when the tires in motion" are accounted for in the specifications of the tires. To put it simply, the figures the tire manufacturer states include the forces exerted on the tire while in motion, such as "increases of weight loading when traversing bumps in the road at speed".
Which make sense, as it would be difficult indeed for us to foresee actual loads in motion."

Those 'tire engineers' are wrong. The test spec for ST tires (FMVSS 109) only requires that they be stressed to 100% of rated load, and be tested for puncture resistance. There is no overload test embedded in that spec. When you tow on a curve there is a constant and huge increase in force on the outside tires that is not allowed for in the testing. When you tow in a cross wind there is a similar increase in force on the leeward tires that can also be in the many hundreds of lbs. Neither of these effects is taken into account unless the resulting force on the tires is less than their load rating.

crollman wrote:

gmw photos wrote:


So yes indeed, it's good practice to follow the recommendations of the trailer manufacturer.

As a design engineer with 40yrs experience and two advanced degrees out of MIT, I disagree. It's in fact naïve to blindly follow manufacturer recommendations in the case of RVs, unfortunately.

The RV manufacturers ignore dynamic forces in sizing the tires they install and recommend for trailers. The result is that the tires will be overloaded when the trailer is in motion, and those overloads can be quite large (580lbs per tire in my case).

Carlisle Tire has a document "Trailer Tires: Tips & Best Practices" that offers solid advice about sizing trailer tires. They recommend taking the trailer gross weight, add 20%, and divide by the number of tires to get an appropriate load rating for trailer tires. The 20% margin will allow for dynamic forces. All of the brand new trailers from several manufacturers that I checked failed this test when loaded to the GVWR. You might try this calculation on your own trailer with factory tires installed and see how it compares.

The tire engineers here on the forum tell us that "the dynamic forces involved when the tires in motion" are accounted for in the specifications of the tires. To put it simply, the figures the tire manufacturer states include the forces exerted on the tire while in motion, such as "increases of weight loading when traversing bumps in the road at speed".
Which make sense, as it would be difficult indeed for us to foresee actual loads in motion.

I wasn't following the RV manufacturers recommendation, I was following the tire manufacturers recommendation.
Anyway, if some people figure the advise received on an RV forum is more accurate that the advise of a tire manufacturer then go for it.