Tire pressures

Apologies on this isnt tractor but still may apply..
I recently bought new tires 10 ply 285 75 16..E rating.. Max air is 88 when cold..
I had 265 75 16 ..D rating..8ply with a max air of 55..
I always I guess thought that the max air was what you kept tires at when cold.. right out of the garage to the air compressor..
Noticed that the new tires that I just got recently had 55 pounds in a 88 tire..
So whats the rule of thumb... and then it starts me wondering about my implement, and tractor tires.. that willhave not to exceed.. # lbs.. I usually will fill up to that number also..

Any thoughts on this..

Open the drivers door and read what it says, then go accordingly to that. If you put a heavy load on your truck use your best judgment if the tires are squatting more then they should.

That is my advise, take it or leave it!

You do not have to run max pressure. Your new tire are stronger than the old ones and if the old ones held up good under load I would not go more than what you had in them. The extra pressure means unless you are loading them extra they will ride harder.

I agree with Brown Swiss, 88 PSI would be for max load conditions. Check the door sticker as that trumps any tire rating. In my opinion 55 psi is ok for normal driving. 88 PSI in an unloaded truck would seem to ride like a lumber wagon.

When loaded I usually run max tire pressure. When unloaded I drop down to 30 in rears and 35 in front. Otherwise the centers always wear out faster for me

Funny about the door post sticker.. says original tires of 235 75 16 .. Front psi 50 rear psi 80.. and that seems high for a 235..

I don't run the maximum inflation pressure on my tires. In passenger cars, I tend to follow what the recommended pressures are as noted on the sticker just inside the door, and they might even be printed in the owner's manual. On my HD 2500 truck, I will run higher pressure when loaded and/or towing my trailer, and lesser when the truck is not loaded. I know when I run the pressure up to 55 psi, the truck rides rather rough. I think I have the tires running around 35 psi for typical driving without a load, and probably around 50 psi when pulling my trailer. On the tractors used in the field and going up and down the road for farm use, I have actual weights on the front and rear axle and the inflate to the appropriate pressure shown in the tire inflation charts based upon that actual weight. I run radial tires on the main tractors used for farming and I want to maximize the footprint for traction purposes and lessening compaction. On the other tractors that are not used much in the field, I pump the tires up to the point where they are not squatting. Implement tires are pumped up to the specifications in the owner's manual for the implement, which they do not squat or show any "cheekiness," for lack of better words.

The "Max load of ___ lbs at ___ psi" that is printed on the tire is exactly that - the maximum load the tire can handle when aired up to its maximum pressure. If the tire is mounted on a vehicle that is incapable of subjecting it to this maximum load then the pressure is adjusted down accordingly. This is why the vehicle manufacturer states what the tire pressure should be for a particular application and, especially with passenger vehicles, this is rarely as high as what the tire could handle. Any more pressure would just make the tire center wear faster and worsen the ride quality. A tire is designed to run at a certain amount of deflection or "squat" to get the best blend of life, stability, ride quality, and fuel economy and the vehicle manufacturer's recommendation for inflation pressure assures that it will run at this deflection for the weight it is carrying.

Who the heck ever made a tire officially sold as having and 8 ply rating with 55 PSI max fill? I am not sure that is even legal. There are DOT and Highway Safety Administration rules that pretty much go like this for truck tires. C-range is 6 ply rated and max of 44-50 PSI. D-range is 8 ply rated and 65 PSI. E-range is 10 ply rated and 80 PSI. F-range is 12 ply rated and 95 PSI. I want to see info on someone selling a truck tire as a "8 ply" with only a 55 PSI max rating. If so, I am surprised they have not been sued out of business.

Tire pressure that is correct has little to do with the max rating on the tire. To work as designed, tires are supposed to squat to the "loaded radius" and that is solely determined by weight versus pressure. Not by "max pressure." That being said, many pickup trucks have stickers showing max rating on the back because driver's are not trusted to fill when needed during heavy loads, and then let air out during light loads.

Yep your right ...MY BAD.. Nexen 265 75 16 load D 65 max psi cold.. Still.. the question remains..

They have to put a rating or limit on the tires. (Just like chemical companies put a limit on how much roundup to put in a gallon of water). That is not what pressure you run with in them though. If they're squatting from a heavy load you can put more air in them up to it's max PSI rating or it's like running them under inflated or almost flat and you'll ruin the tire. Yes the door post as others have mentioned will tell you what PSI to run in the tires. They have tested and determined if you do that the vehicle will perform its best. Then too just like the tire mfgs the car mfgs have to put a rating on them also.

The problem I have with all this is that I don't carry maximum tire rated loads ever. As a result and in wanting a softer ride, I air proportionally when I can.

My go to town and back 2011 Silverado has the tire monitors. Tires are spec'd to run at 35 psig and the load at that pressure is stated on the sidewall, and on the driver's door jamb of the P/U. Problem I have with my tires is that the tire monitor starts squealing when you hit 32 psig. On that particular vehicle, since I am running 20" wheels with a shorter sidewall than the normal 16s or 18s that come on the vehicle I don't mind the prompt. But if I were running standard 78 series tires I'd get real tired of the babysitter as I'd be running them quite a bit lower.

To my amazement, I just put on a new set of tires, Goodyear LS2s, same as I had, and the tire wear was even across the tire, not high in the middle as I expected would happen with the wide tire, high pressure and light load.

Some tire companies provide inflation charts based on the load that is on the tire. In my research, I have found that for a given size and load range, the inflation rates are the same from brand to brand. Here is one of Michelin's inflation charts:

http://www.michelintruck.com/reference-materials/manuals-bulletins-and-warranties/load-and-inflation-tables/#/

that is the ONLY proper advise hopefully folks take it.

cars and light trucks were designed to have a certain tire size/pressure for best ride, fuel economy and SAFE handling. THe pressures listed in the door post are the only pressures you are to use. IF the vehicle manufacture allows something different for different loads they will say on the door post or in the owners manual. anything else carries risk of injury or an accident or at least damaged tires/vehicle. I'm amazed how many mechanics don't even know or follow this.

even some modern trailers have tire pressure guides.

yup. if the centers are wearing fast they are over inflated.

if under inflated they outsides will wear too fast.