Tire Ratings

[hohenwald48]

Correct me if I'm wrong, but aren't all tires of the same type (ST/LT) and the same size (225 75R15) and same load range (C,D,E) rated just the same (as to weight capacity) regardless of manufacturer?

[JIMNLIN]

hohenwald48 wrote:

JIMNLIN wrote:
If I understand the question a example is a Provider and a Carlisle ST235/80- 16 E has a 3520 lb capacity.

The same size Maxxis and Marathon ST235/80-16 E has a 3420 lb capacity.

That's what I was looking for. Interesting that the Carlisle's are rated at 85psi and Maxxi's at 80psi. Guess that's the reason for the extra load capacity.

Actually just looked at Carlisle website. The ST235/80-16 E is rated at 80 psi also. Check it out

[time2roll]

Virtually all ST of same size and pressure will be same weight rating.

LT will have different load ratings but within LT class same size and pressure again gives same weight rating.

Now someone will prove me wrong however it will not be significant.

[CALandLIN]

JIMNLIN wrote:
If I understand the question a example is a Provider and a Carlisle ST235/80- 16 E has a 3520 lb capacity.

The same size Maxxis and Marathon ST235/80-16 E has a 3420 lb capacity.

This is true and there is still another load capacity not mentioned, 3500#. There is another FMVSS standard that addresses this subject. In part, it says that when a particular tire size is manufactured with multiple load capacities they will all default to the lowest unless individual documentation is provided with the vehicle.

Of course to do that the vehicle manufacturer would have to start advertising tire brands and that don’t often happen so when there is a conflict such as 3520# tires on a 7000# GAWR axle the vehicle manufacturer will just build the weights down to a 6750# GAWR axle so the defaulted load capacity will work.

Because of the way tire industry standards are written a RV trailer manufacturer can provide NHTSA a blanket letter stating they only use 3520# tires on 7000# axles and list the axles as 7000# GAWR. Tire industry standards places the responsibility in the hands of the installer to insure the replacement tires are equal or greater in load capacity when compared to the Original Equipment tires. That means “read the sidewall”. But you’re still going to find Maxxis replacing TowMax.

[CALandLIN]

ktmrfs wrote:
For a given tire size and ply rating they are the same IF and ONLY if they have the exact same load INDEX. They have replaced the ply rating and size to determine load rating with a 2 or 3 digit number giving the load index. load index goes from around 70 to at least 150. For a given tire size and ply rating the load index can vary slightly. For instance, on my truck tires I've seen load index of 116 or 118 depending on specific tires.

Although you will find load index information on most all LT & ST tires along with a load range letter. Only the load range letter is official for those tires. It's a long story and you can find the rational for it in NHTSA's rules change package of 2007.

[hohenwald48]

JIMNLIN wrote:
If I understand the question a example is a Provider and a Carlisle ST235/80- 16 E has a 3520 lb capacity.

The same size Maxxis and Marathon ST235/80-16 E has a 3420 lb capacity.

That's what I was looking for. Interesting that the Carlisle's are rated at 85psi and Maxxi's at 80psi. Guess that's the reason for the extra load capacity.

[JIMNLIN]

If I understand the question a example is a Provider and a Carlisle ST235/80- 16 E has a 3520 lb capacity.

The same size Maxxis and Marathon ST235/80-16 E has a 3420 lb capacity.

[MFL]

Terryallan wrote:
Yes you can get the same rating in all brands. But you won't get the same quality.

I agree with this statement, and also think the OP is correct for the most part. IMO, even though rated the same, there has to be some real world difference, in that some, same rated designs could actually carry more load than another.

May not be relevant, but some, same weight rated tires, can carry the load at higher speeds.

Jerry

[ktmrfs]

For a given tire size and ply rating they are the same IF and ONLY if they have the exact same load INDEX. They have replaced the ply rating and size to determine load rating with a 2 or 3 digit number giving the load index. load index goes from around 70 to at least 150. For a given tire size and ply rating the load index can vary slightly. For instance, on my truck tires I've seen load index of 116 or 118 depending on specific tires.

[hohenwald48]

Trackrig wrote:
No, the load capacity is not always the same between mfgs. I see this on my truck tires - 265/70R17. Capacity ranges between 3300 to 3400 per tire. Not a lot of difference, but there is a difference. I noticed the same thing when I recently bought 16" TT tires.

Bill

Can you give an example? Where different mfg have differing weight ratings for same size and load range tires? I've been looking and can't find any.

[Trackrig]

No, the load capacity is not always the same between mfgs. I see this on my truck tires - 265/70R17. Capacity ranges between 3300 to 3400 per tire. Not a lot of difference, but there is a difference. I noticed the same thing when I recently bought 16" TT tires.

Bill

[gmw_photos]

hohenwald48 wrote:
Correct me if I'm wrong, but aren't all tires of the same type (ST/LT) and the same size (225 75R15) and same load range (C,D,E) rated just the same (as to weight capacity) regardless of manufacturer?

I believe you are correct that a tire, of a given size, in a given type, at a specified pressure, has the same same load capacity. I think that standard is set by the tire and rim association, to ensure consistency across brands.

Hopefully one of the tire engineers will jump in and correct any mistakes made in these statements.

[Terryallan]

Yes you can get the same rating in all brands. But you won't get the same quality.

[ScottG]

Deleted - didn't read post correctly.