Standard load tire has higher rating than C tires?

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volk06

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I've been looking at the Cooper AT3 tire next on my f150, in 275/65/18. The truck came from the factory with load range C, how ever now that things changed a while back I do mostly all highway, a little off road, and not much towing/hauling. So I was thinking of just getting the standard load AT3 tires, for better ride and what not.

So I was comparing the specs and have a question. Why do the standard load tires have a higher max than the load range C tires?
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Tire serivce load sidewall Diameter tread width max load tread depth

LT275/65R18, 113 S, C OWL 32.1 8.9 2535 16.5

275/65R18 116 T 560 A B, STD OWL 32.14 8.73 2756 13


Could having less tread depth but the same diameter enable the tire to have more air volume for a higher load or what gives?
 
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And they require much higher pressures to carry that load so your ride quality may suffer. If you run them at P tire pressures, they will build up a LOT of heat.
 
you have to reduce the load rating of p-metric tires on trucks.

by a factor of 1.1

ie divide by 1.1
 
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Originally Posted By: Rand
you have to reduce the load rating of p-metric tires on trucks.

by a factor of 1.1

ie divide by 1.1


Why is that??
 
Originally Posted By: volk06
Originally Posted By: Rand
you have to reduce the load rating of p-metric tires on trucks.

by a factor of 1.1

ie divide by 1.1


Why is that??


Because that is the way it works.

If you want to know why it works that way, you will have to ask the engineers who set this up in the 1960's.
 
Originally Posted By: CapriRacer
Originally Posted By: volk06
Originally Posted By: Rand
you have to reduce the load rating of p-metric tires on trucks.

by a factor of 1.1

ie divide by 1.1


Why is that??


Because that is the way it works.

If you want to know why it works that way, you will have to ask the engineers who set this up in the 1960's.


Well if anyone would know, it would be you capriracer, with all your years of experience in the tire industry. Surprised you don't have any explanation or know why.
 
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So let me see if I have this right: if I run a P225/75R15 tire on, say, my Cadillac, I can run it right at the weight listed on the sidewall. But if I put the same tire on, say, a Ranger or an E-150 (225/75R15 was a pretty common size on older pickups and vans), I can only load it to 90% of that weight? This utterly fails the laugh test!
 
^ nah it's true. Just imagine the truck's stiffer springs pushing down harder on the tire when it hits the same bump.

For another analogy, imagine a 300 hp over-the-road truck engine compared to a small block in a corvette. The truck engine is way more overbuilt. The corvette engine could do it for a while but should be derated by a margin for longest life.
 
I have two different load ratings on my 215/85-16s ... one for single and one for dual.

All load range "c" dictates is that it's for a real light duty truck. A load range D or E tire will have a much higher weight rating.
 
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Originally Posted By: Miller88
I have two different load ratings on my 215/85-16s ... one for single and one for dual.

All load range "c" dictates is that it's for a real light duty truck. A load range D or E tire will have a much higher weight rating.


C is the entry LT tires, dictating it is a 6 ply, E is a 10 ply respectfully. There aren't that many D's out there. Higher the ply/ load rating the rougher the ride.

I know how the tires work just never seen a standard load with a higher load, but then again never paid attention to standard load tires before.
 
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Originally Posted By: volk06
Well if anyone would know, it would be you capriracer, with all your years of experience in the tire industry. Surprised you don't have any explanation or know why.


I can only speculate - and I speculate it has to do with 2 things that are part of the duty cycle of a pickup - the suspension is stiffer so the tire has to absorb more of the energy when it encounters rough roads, and that tires on pickups are expected to endure some off road.

Originally Posted By: Jarlaxle
So let me see if I have this right: if I run a P225/75R15 tire on, say, my Cadillac, I can run it right at the weight listed on the sidewall. But if I put the same tire on, say, a Ranger or an E-150 (225/75R15 was a pretty common size on older pickups and vans), I can only load it to 90% of that weight? This utterly fails the laugh test!


See what I have to put up with. It's been like this for 50 years and there are folks who just don't believe it to be true - even though they could look it up to be sure BEFORE they post.
 
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