P235 75 15XL tires

[Hodum]

Originally Posted by CapriRacer

Because at 80 psi, the load carrying capacity of the ST tire was 2830#, while the P type tire is 1985#. That's operating the tire at 143% of its rated capacity.

You need to seriously rethink this.

Somebody is not adding correctly. Even derated to 1,985# I have a 2,710# safety margin before reaching the rated capacity of the Michelins. My trailer, loaded, will weigh about 10,000#. Take 800# for tongue weight leaves 9,200#. Six tires derated to 1985# =11,910# My tires will never reach anywhere near there rated load carrying capacity. The ride difference is great. I have run Michelins on all of my cars and trucks for years, and though I know there are other great tires I dare not change because of the quality of ride and longevity of the Michelins.

[Hodum]

Originally Posted by Ridgerunner3

After months of reading tire threads and asking questions, I just ordered 5 Michelin P235 75 15 XL tires for my 6300# Safari 25. Good bye to ST tires.

I think that you are going to be one happy camper the first time you pull your 6,300# airstream on these super smooth, sidewall flexing, great handling, 7,940# rated Michelins.

[bwoodtx]

I know when I put them on my 1997 31' Excella wide body, it made all the difference in the ride. Oh, did I mention this was AFTER I had a Carlisle ST Load Range E tire blow catastrophically and do $7000.00 yes $7000.00 worth of damage to the above mentioned trailer.

[BlackAces]

Originally Posted by SuperTrouper

Sure, Article VI Section D:

DOT 49 CFR Part 571 Docket No. NHTSA-03-15400 RIN 2127-AI54

"For the final rule, the agency has also decided to retain the de-rating factor of 1.10 for P-metric tires used on non-passenger car vehicles. For non-passenger car vehicles equipped with P-metric tires, the vehicle normal load shall be not greater than the derated value of 94% of the tire load rating at the vehicle's placard pressure. This de-rating provides a greater load reserve when these tires are installed on vehicles other than passenger cars. For the first time, this final rule requires light trucks to have a specified tire reserve, the same as for passenger cars, under normal loading conditions."

Brad

Here is what the regulation really says. It's often misunderstood. This is the most current and official document.

Tire selection and rims and motor home/recreation vehicle trailer load carrying capacity information for motor vehicles with a GVWR of 4,536 kilograms (10,000 pounds) or less - Federal Motor Carrier Safety Administration

[SuperTrouper]

Originally Posted by BlackAces

Here is what the regulation really says. It's often misunderstood. This is the most current and official document.

Tire selection and rims and motor home/recreation vehicle trailer load carrying capacity information for motor vehicles with a GVWR of 4,536 kilograms (10,000 pounds) or less - Federal Motor Carrier Safety Administration

So 4.2.2.1 and 4.2.2.2 say P tires on trailer with no passengers max load divided by 1.1 or 2183lbs=1985lbs right?

[willapus]

I stayed with an lt tire because of all the complaints with the g.y.m.'s, but scaled down closer to the original size for my TT, 7.00-15 load c to lt 225/75 r16. "P" tire load ratings are not equal to LT load ratings. The increased height of the center of gravity on trucks decrease the load capacities of P tires by about 10%. The p tires sidewalks aren't as rigid as the lt's. I'm hoping the new lt's on the TT and TV will help minimize the sway.

[switz]

That 1,985 pound load number is correct for the 15" Michelin tire in a derated application.

[CapriRacer]

Originally Posted by bwoodtx

Thanks, had not seen that before. Now I understand-more government regulation. Everything that was postulated in there is a severe case example. But, it is what it is, thanks for the info.

I will continue to run my "P" metric XL's

Actually, the derating of P metric tires for Light Truck, van, and trailer usage predates the government regulation by a decade. The government adopted the existing standard.

And to answer the question: The tire does indeed know it is on a trailer. It is being asked to do different things than if it was on a passenger car. (Ok, Ok! Tires are inanimate object and can't "know" anything. Nevertheless, trailer usage is different than usage on a passenger car. )

And lastly:

Originally Posted by Hodum

Somebody is not adding correctly. Even derated to 1,985# I have a 2,710# safety margin before reaching the rated capacity of the Michelins. My trailer, loaded, will weigh about 10,000#. Take 800# for tongue weight leaves 9,200#. Six tires derated to 1985# =11,910# My tires will never reach anywhere near there rated load carrying capacity. The ride difference is great. I have run Michelins on all of my cars and trucks for years, and though I know there are other great tires I dare not change because of the quality of ride and longevity of the Michelins.

The tidbit of information was not part of this thread. So while I apologize for an un-necessary alarm, I was merely acting out of safety concerns.

[perryg114]

Trailer tires at least on an Airstream have an easy life compared to being on a car. Trailer tires live an easy life comparable to the rear tires on a front wheel drive car. Yes there are some side loads when turning with a dual axel trailer but most of the time turns are not that extreme. Because of the extra flex in the sidewall car tires are not going to suffer as much stress as a more rigid tire during turning. If you put 80psi in something it is going to get rigid. When it blows it will destroy your trailer. Also if you look at the carcass of a trailer tire and a car tire the car tire is much more beefy. The weight numbers for trailer and car tires show this as well.

Perry

[Bill M.]

Trailer service can be hard on tires. Here are some reasons: The suspension travel is very limited on most trailers, leaving the tire to take up all the shock from a bump or pothole. Multi-axle trailers may be hitched wrong and have more load on one axle and less on another. Construction and loading of the trailer often can put excessive load on one tire. Misaligned axles can put on side stress. Tight turns puts on side stress. My trailer seems to hit more curbs and potholes than the truck.
That said, I run P235's because I think the trailer really needs a good tire.