The "N" on the side of our football helmets stand for knowledge.

 

Bought the truck used with Michelin 235 load range D's already on it and I couldn't keep them from sucking up every thorn, nail, screw, staple and anything else sharp from off the road.
They had 50-55psi max pressure rating and the fronts always wore on the edges quite a bit from cornering in town. From the wear pattern they were just calling for more air and I couldn't give it to them. Like Phox, I didn't like the flex in the sidewall of the "D's".. When it came time, I splurged and replaced them with "E's"....
The load range E's aired up to 80psi can be harder riding in town when unloaded. I sometimes air down the rears to 55 or so and my backside is much happier.
I've been keeping almost max pressure(75-80psi) in the fronts because of that extra heavy chunk of Indiana cast iron that I carry around up there...
The Load Range E's, aired up to max wear nice and evenly too! I didn't realize 2 extra plies made so much difference in a tire. I'm sold on keeping E's on my baby...

 

Plies are not what determines Load Range E vs Load Range D. That is determined by testing parameters of a given tire.
A lot of the tire stores will tell you this is a 10 ply tire.....it's just a bunch of hype. Have you ever looked at a tire section cut from a tire? Most tires are 1 ply or 2 ply or sometimes 3 ply. The plies are referring to the number of polyester cords in the carcass of the tire. It does not include steel belts or nylon or rayon ply caps.

 

Yeah I know.. The key word is 10 ply "RATED"... rolleyes
LIke "lifetime lubricated" bearings... WHOSE lifetime? Mine or the bearings?

 

Ok... I'll add my 2 cents here about tire pressure....

I've got Big O XT 265/75 R16 tires Load Range D (Picture is in my gallery)

Yes I keep a tire guage in the truck!

I've been inflating the tires to these pressures...

EMPTY or LIGHT LOAD

50 PSI Front
40 PSI Rear

LOADED to MAX WEIGHT

60 PSI FRONT
60 PSI REAR

SAND / SNOW / MUD - This combo works great for these conditions...

40 PSI FRONT
35 PSI REAR

I've got constant fuel mileage of about 19.5 - 22.0 MPG for the last 3 years. My last set of tires lasted 45,000 miles! There was less than 1/16 difference from the edge of the tire to the center!

 

IMO Internal air volume inside a tire is what determines load carrying capacity. Thats why a larger tire can carry more weight at a lower pressure. They have much more internal volume to make up for the difference in pressure. It is the amount of air in the tire that determines how much heat the tire can dissipate. Heat is a tires #1 enemy. If you overheat a tire one time it can cause a tire failure right away or maybe not for 3-4 years down the road.
That being said, I feel that most people that don't tow heavy, run too high of an air pressure. The sole function of air pressure is heat resistance. If your not going to be heavily loaded you don't need to run 2500lb extra air pressure in the tires. If it's not overheating at the lower pressure, than the higher pressure won't gain anything except less ride comfort. Also if the tire can't flex then it can't do it's job correctly, which is to carry the load and absorb shock. Most people disregard the later part in fear of losing safety margins.

If your just driving around town unloaded most of the time you'll never overheat your tires at 50-55psi. Sure there something to be said about fuel economy but I think in around town driving any gain would be minimal.

My stock tire size was E load LT265/70/R17

Max rating 3195 lbs at 80 PSI

My current size is D load LT295/70/17

Max rating 3415lbs at 65PSI

From what I've read here the rear axle of a typical truck may weigh around 3750 lbs , empty. Why would I need to run my tires at 65 psi and have over 3000lbs extra capacity and much rougher ride.

I run my tires at 46fr and 40rr empty and 65 on the highyway towing my trailer. I run 70 psi in my d load trailer tires (65psi max) because ride isn't a factor.

I feel my truck rides much smoother at the lower pressures. Why drive around on a bunch of bricks if you don't have to? I think if people did an infared pyrometer test of tire tempatures while towing at high speeds at max PSI on the highway, then tried to get the tires to the same tempature just driving around with the truck empty at lower pressure, you'd have to go really low on pressures to get to the same tempature.

Sorry for the ramble and again these are just my opinions, not everyone can run as low a pressure as I do.

 

Remember,
PSI is 'Pounds Per square Inch', keep this in mind.

If you have a 3" cylinder and put 80 psi of air/fluid in it, you will have

3" * 80psi = 240 lbs of lift

Now take a 3 1/2" cylinder and place 70 psi of air/fluid in it, you will have

3.5" * 70psi = 245 lbs of lift

Now, if you can equate that to tires, the smaller tire has less surface area and will require more pressure to lift (or support) the same load as a larger tire with more surface area.

Hope its all clear as mud now.... LOL

DuaneW.

 

Load range is different from maximum load/load index; if it wasn't BFG ATs could be called load range E, but they aren't so they don't. From what I understand load range takes into consideration side loads, for hauling heavy payloads and towing.

 

uh.....
I think you meant

[(1.5")^2 * pi] * 80psi = 565.5 lbs of lift



I too run my BFG's at "low" pressures when the truck is unloaded. the tires wear more even, I've got more traction, and the truck rides better.....
run the proper pressure for the conditions.....

--Berne

 

Maximum load and load index are determined by the size of the tire and that is determined by The Tire and Rim Assoc. Load Range is kinda determined by the industry, meaning what consumers expect. Then the tire is designed to meet consumer expectation and reality testing in order for it to pass testing for a given load range.

As for BFG ATs could be called load range E, not true if they can not pass the required testing. Why would a tire company downgrade their tire and charge less money for it? Doesn't make sense. Have you noticed how much more money a Load Range E tire cost vs Load Range D?

There is no doubt that a Load Range E *IS* a better designed tire than a Load Range D regardless of the load carrying capacity. Most Load Range E will have a Nylon Ply Cap or Full Nylon belt cover or even and additional ply in the sidewalls. This allows it to meet or exceed the testing parameters.

 

Im running 60 psi in all my factory tires.. although, one slowly leaks down over the course of a week, about 10 lbs.. because I have a nail in it, and have yet to get it plugged.
Scott

 

There IS no factory pressure for 285s!! Once you change size, you're flying blind.

Actually, tires will wear more whether they are too high or too low. Running your 285s at 65 psi will run the centers out of them-- too much pressure, at least when empty.

Factory recommends 45f/40r for 265s. 285s need less than that. I'd run a 285/65r16 @ a maximum of 50F/45R when empty. Obviously you have to air up for towing heavier loads.

Think about the units of pressure: POUNDS PER SQUARE INCH. When you go to a larger tire, you have more square inches. That means for a given POUNDS (weight on tire) that pressure needs to be less. For example, say you have 2100# on a front tire. To support that same 2100# with more AREA (more square inches) requires fewer POUNDS PER SQUARE INCH inside the tire..

Capeche?

jlh