Tire Load Range Question

[GWBourne]

LT265/70R17 121/118 Q E OWL 7. 00 - 9. 00 8. 00 10. 80 31. 90 8. 25 3195 18. 0

LT285/70R17 121/118 Q D OWL 7. 50 - 9. 50 8. 50 11. 50 33. 00 8. 85 3195 18. 0

how can one tire be a "D" rated tire and the other be an "E" rated tire when they both have the same rating as my factory tires of 3195lbs.....



im looking at the cooper Discoverer STT... .



thanks.

Grant

 

[Alan Reagan]

Could be a misprint.

 

[JohnnyH]

Dont quote me on this, but I remember reading that it had something to do with the sidewall or flex. Something like that.

 

[Alan Reagan]

It does have to do with the flex. The D is an eight ply where the E is a 10 ply. Both tires may be rated to carry the same weight. What you may want to look at is the load index instead of the load range. The load index is the weight the tire is rated to carry at a certain air pressure. The D may carry the same weight but at what pressure? Plus, the flex in a D is unacceptable with the weight of the truck. Makes for sloppy steering.

 

[BHolm]

Load capacity increses with BOTH size and load rating. The 285 is the bigger tire, so even with a D instead of E rating, it is in the same ballpark for load capacity.



As far as a D tire flexing too much and giving "unaceptable" ANYTHING, I beg to differ. The D rated tires are generally a 65psi max and E's are generally 80psi. I have had both on several trucks and have never found the larger D rated tires to be an issue. My '03 QC went from the 265 E tires to 285 D tires 30k miles ago. That would be 30k miles of heavy towing on a daily basis. Never had a problem. If anything they allow you to carry the same load in more comfort. It's not like these trucks are so softly sprung that you need rock hard tires to compensate.



I am running 285 D tires on both my srw trucks right now and plan to stick with them. I would also be a little shy on the Cooper. I didn't get many miles out of them when I tried them. I've had better luck with BFG AT's personally.

 

[Alan Reagan]

So we don't confuse load range with load rating, the load range identifies the strength of the sidewall. Load rating is an indication of how much weight the tire will carry. The reason the D range tires are only rated for 65 psi is the strength of the sidewall. E series are stiffer and will typically carry a higher psi when towing heavy. The unacceptable flex I'm talking about is the type you get when towing heavy with a lower air pressure. When a truck passes you and you start to wiggle a little, some of that is caused by tire flex. Or when you turn sharp and the tire tends to flex and roll. If the tires have a stiffer sidewall and are "aired up" then there will be less of that. Also, tire manufacturers recommend that you never go down in a sidewall rating from what comes as OEM equipment. If you are following the guidelines on the D tires and have adequate air pressure to maintain a required load rating, you probably won't get any unacceptable flex. When I sold my 01 Ram, the OEM Michelins had 118,000 miles on them. About 40%/60% towing/empty. They were Range E.