??? on tire load ratings...

MrQuadrasteer · January 17, 2004

I tried a search but didn't find what I was looking for. I'm finally getting some tires in the next week or so, so been looking around. My truck came with E-loads, but I never haul near my max capacity. I *might* once in a blue moon haul a car on a tandem axle, but that's rare. About my heaviest load is my 600lbs bike.

So, can someone supply the actual numbers that correspond with the different ratings ?? What about the LT rating ?? I looked thru a few sites and none really address it directly, but I did read there is no standardized rating system for truck tires...

FWIW, I'm gonna try and fit 265/75-16's in place of the 245's from the factory. Hope it clears the rear steer....

Thanks for any help.

smoke

bfrd22 · January 17, 2004

Good Question and not easy, This is my understanding, Truck tires although are rated C.D.E etc. It reffers mainly to the number of plys used in the construction.

Each manufacture will have thier own tire rating as unlike a passnager tire there really is not true rating system.

Speed vs load vs temp vs air pressure vs ply # and construction all come into play.

And E rated tire would be I believe a 10 ply tire, strong side wall for towing. and good handling. I ran Avon E rated AT's and liked em, A little stiff ride but droped the pressures to 32 psi and ran well, Towing or hauling 55 lbs,

A radial needs a certain psi, at X load at a given speed to disipate heat properly.

Or the seperate (Ford fiasco). An E rated tire can run Higher speeds at weigth for a longer period than a D rated tire or C rated.

If your not hauling often, nothing wrong with D rated tire, but if your hauling a trailer around 75% of capacity stick with the E rated and bring up the tire pressue as shown on the side walls while hauling or towing.

Check out the below site, but search around for the Truck Tires area (Highway tractor stuff), lots of information on loads speed and air pressure, you may have to look at some actual tire rating and the associated links.

www.michelin-us.com

SilveradoWV · January 17, 2004

LT tires are rated by letter. To find out what ply they are take the letter of the alphabet and multiply it by 2! For example E is the 5th letter times 2 which is a 10 ply. I know people who run Load Range C on 2500 Dodge Ext Cab Turbo Diesels but tow very little. I would definately go with a Load Range D.

Shotgun · January 18, 2004

I took the load range E's of the day after I bought my truck.I have always believed that the load range E tires are and over kill on any truck less than 10,000lb GVW or for trucks used in a commercial type scenario that will be loaded frequently,I.E. tool boxes loaded with tools,parts ,commecial carrier.I pull heavy loads ,including my travel trailer,a gooseneck with a JohnDeere 2650 tractor and implements pretty regularly and the load range D tires have been more than adequate. This includes loaded trips to Gatlinburg,Tn. & Gunnison,Co. from south Louisiana. Another benefit I enjoy from the Load range D tires is a much better ride.

Shaners · January 18, 2004

A set of 265/75/16 load range "D" will have about the same carrying capacity as your stock 245/75/16 "E" tires.... If you don't carry/tow alot, and if you want to +1 your tires, then a "D" rating is plenty!!!

MrQuadrasteer · January 18, 2004

Good info .

Thanks, gang.

Ben · January 18, 2004

P rated is passenger car tire.

LT rated is light truck tire.

When P rated tires used to haul/tow heavy, they need to be DE-RATED min 9% of it's max sidewall weight carrying capacity, while kept at it's max pressure. Why only 1/2 ton trucks come with OEM P rated tires, while 3/4 ton and larger trucks only come wtih LT rated tires.

Both P rated and LT rated have weight carrying capacity ratings. Just different methods. P rated uses number to designate a load carrying capacity. LT tires use an leter to designate a ply rating (today's are only 2-3 actual plys, but old days actually had those numbers of plys in the sidewall). You'll have to look at the manfacturer's tire charts to see the weight carrying capacity to letter and tire size.

Best tire info site found and easy to understand info Also has wheel info.

FourWheeler 9% de-rate of P rated tires used in LT app There are several other sites that note the DE-RATE requirement on P rated tires used in LT app.

auto_god · January 18, 2004

Maybe I can clear up a few questions about LT tires. C, D, & E are ply "ratings", you may not actually find the tire has 6, 8, or 10 plys in them, it simply means that, as an example a C tire can be inflated to 50 PSI. In the bias ply days you needed 6 plys to contain 50 PSI, 8 plys to contain 65 PSI & 10 plys to contain 80 PSI. The reason this is important is that a tires load capacity is directly related to the inflation pressure in it, it is actually the chamber of air in the tire that sustains the weight of the vehicle, not the tire....the tire is simply a means of containing the air.

So what does this mean in the real world? It means that the recommended inflation pressure & tire size on the sticker on your driver's side door is what is required to sustain the full rated load of your truck. During everyday empty driving around this is far higher than what is necessary. You will probably also note that the front & rear inflation pressures are different. When running empty, you could safely air down the rear tires to the pressure recommended for the fronts, they will wear more evenly, and improve wet grip noticeably, however you must air them back up if you plan to load the truck.

As far as putting larger tires on your truck goes, as I said above, the chamber of air is what sustains the weight of the vehicle.....so, bigger chamber of air, higher load capacity given the same inflation. So as someone else noted, a larger tire can provide the same load capacity at a lower inflation pressure. I don't have my conversion charts handy to look up how much less pressure a 265 would require to sustain the same load as a 245, but off the top of my head I think they would require about 10 PSI less.

Bottom line of all of this, if you are going to put 265's on check the recommended inflation for the rear of your truck with the 245's on (probably 80 if it came with E's on it). 80 PSI - 10 PSI for the larger size = 70 PSI, therefore a D rating is inadequate to sustain the full rated load of your truck (max pressure = 65 PSI with D rated tires) so you will still need E rated tires with 265's to maintainn you trucks load capacity. In real world driving, I would take the recommended pressure for the front 245's, subtract 10 PSI & use that inflation for all 4 tires in 265's. Again, the tires must be aired back up if you are going to load the truck - this includes towing.

Hope I made it all clear as mud.