Tire Load Range Ratings

I was at the local tire store today getting a new set for our Silverado and a lady came in to the bay next to me to get a set for her 2007 Ram 2500 Long Bed 4x4. I struck up a conversation with her about how nice her truck was and she commented that she only uses it for pulling her trailer and it sits otherwise. Anyhow, she ended up buying a set of 285/70/17D tires with a rating of 3195# at 65psi. The 265/70/17E tires that I got are also 3195# but at 80psi.



OK, now I apologize if this has been specifically answered here before, but I couldn't find the answer I was looking for using the search function. What exactly defines a D rated tire as a D or an E rated as an E etc. ? Is there a specific formula that determines its rating or is it based on weight? I guess the easiest way to ask it would be why is a 285 D rated and the 265 E rated if they both can handle the same weight? I've never been one to change tire sizes on my trucks and I'm not planning to start now. I'm just not sure I understand exactly what the specific ratings mean.



Thanks in advance.....

 

E rated tires are 10 ply and D rated are 8 ply

The reason they can support the same weight is because the 285 is a bigger tire. This means that it turns slower and will not heat up at the same rate that the 265 will

 

There is no such thing as an 8 ply or 10 ply tire. That method of molding tires and the rating system ended 20 or more years ago. Tires are now Load Range E "LRE" which is similar to "10 ply rated" and means the tire is capable of carrying the same load at the same inflation pressure as the same tire with that number of plies was years ago.

LRD tires are normally inflated to 60 or 65 psi, LRE to 80 psi, LRG to 110psi, etc.

It is actually the air that supports the load, not the tire. The tire must be strong enough to hold the rated air pressure indefinitely under all road and load conditions.

The manufacturer using industry standards determines that a certain number of belts, in a certain size or thickness, of a certain material, is capable of being inflated to 80 psi and carrying the industry standard weight of that tire therefore the manufacturer calls it a LRE tire.

Tire manufacturers build tires using their own designs and techniques which they certify as meeting SAE/DOT standards. All tires of a specific size such as LT235/80-R17 LRE are theoretically rated to carry the same weight at the same inflation pressure. I think they are subject to testing and proving by industry groups and government inspectors.

 

Tires

For a little more money an E rated tire supplies a much stronger sidewall and piece of mind. My '98. 5 w/popup had a total weight of 8600# with me driving when the right front D rated Bridgestone tire load rated to 3305#(per tire load was 2150# w/camper) @ 65 psi blew out @ 65 mph almost launching me down a canyon on I-15 south. $3300 damage in seconds. Preceeding this were multiple flats and cuts too. I switched to Toyo E rated M-55's on that vehicle and continue with E rated Toyos on my present one. No flats,no failures to date. These things are heavy.

 

When I switched from 17" tires to 19. 5" tires I found a 225-70 (I think) 19. 5 was the same dimensionally as the 17" but a 1/2" taller, which BTW corrected my speedo based on my GPS... . BUT the 19. 5 tires were easily 50% heavier than the 17" and at least 50% heavier than the 16" LRE my 5er has on it... . in a tire that again is about the same dimensionally at the 17"... I can lay the 19. 5" on the ground without a rim and stand on the sidewall and not collapse it like I can on the other tires mentioned... and I should say, this is limited to the tires I've tested when deciding to change tires... the only exception was the 16" LRE I found at camping world in a Goodyear that was over $300 each... .

As you look at tires... . look at their actual weight, and the DOT standard for mileage, treadwear... etc on the label of the tire... the base tire tested was rated 100/100/100 so any numbers higher than this are better than the standard... . its not uncommon to see thread wear range from 125-300 as an example between 2 tires... . one reason is the tire compound and the other reason is the amount of new rubber on the tire... premium tires just have more rubber.....

hope this helps...

 

So is there a substantial drop in MPG's based on the added weight of wheels and tires??

 

I've not seen any difference in MPG..... its nothing more than adding say 250 lbs, more or less, like something you'd throw in the bed...

 

Good Post



PSI is what characterizes the load rating these days...

No. . 10 ply rating and 8 ply rating. . The tires are most likely 2 or 3 ply.





The lady got screwed... when you tow you want PSI. I run my 285's at 65psi front empty. . why would I wan that to be the max?



There are a couple of 285's that are LRE, Toyo and Nitto. . I run the Toyo's because I won't run a LRD on a HD truck. . I like pressure, they are cooler running, and handle better.

 

Tires/ Load Range / And such

I have a simply question and I want to see how many different answers I get.



We are getting a 990 Arctic Fox camper and as I'm sure many of you have read the various replies about what we can and cannot haul with our 3500 SRW and Toyo 10 ply or load range E tires.



We have hauled a 10 foot camper, Lance and then an Alpinlite on our 91, 2500, 95, 2500 and now the 03 3500 all three being SRW with Toyo's after the ones they came with needed replacing.



We drive a speed that the conditions permit but never over the speed limit as we have a heck of a lot more time than money.



On a side note we had a 1973 3/4 ton 4 X 4 Chev that hauled a 10 footer that I built in 1970 that weighed a lot more than our Lance or Alpinlite. I have no idea what it weighed but it was one heavy sucker. Used Ride Rite air bags when hauling that.

That truck also had Toyo's all season tread.