Is 51 PSI too much for an 18" tire?
 

I have a set of Goodyear Wrangler 275-65R18 tires on my truck and it says on each tire that the max PSI is 51 which seems high. They were all in the 30-32 range so I put 40 pounds in each of them. What do you guys recommend?

Those are the same tires ours came with, and they were inflated to 40 IIRC when we bought the truck. The door sticker says 34 PSI. However, when we replaced the Goodyears with Michelins, America's Tire put 40 in them. They said the 40 would roll easier, and wear better.

I think (in general) that you don't want the cold pressure to be at max, because once the tires warm up, you will be over pressure.

It came with Michelins on a plain set of 17" steel wheels so I bought these wheels and tires from a guy that were on his 2016 XLT so the door sticker wouldn't apply. I'll just go with the 40 PSI and see what happens. By the way, I've had the truck for 15 months now and have only put 2400 miles on it so far.... :-huh

That is a maximum amount not the amount that should be in there. I'd say you're good with the 40 PSI you went with.

I've always run my tires with the max on the tire and not what's on the door. and some times up to 55 psi. That's for a smooth ride for the wife car (not mine). 10,000 people will say I'm wrong but I don't care; I go for rolling resistance and fuel mileage. That old Ford Explorer problem came from soccer moms not knowing the vehicle was built on a truck chassis and the 4wd's were going to ride stiff. Ford was trying to appease them along with the tire manufacture, Firestone. It was all BS and should not have happened. My wife's 2 Honda Civics had had 45 psi in her tires for over 20 years and she has never complained.

If the tires are the stock size g with what's on the door. That is most likely to give you the correct ride and wear. If you're changing sizes, carrying extra cargo, etc., you might want an adjustment.

And I'd bet that the center tread wears a lot faster than the outer treads.

In addition to the maximum inflation pressure you'll also find the maximum load capacity in pounds on the tire sidewall. What they're saying is that that particular tire can support that much weight at the rated max speed for that tire at the maximum inflation pressure. It does not mean that you should run them at that pressure all the time. The tire pressure on the door sticker is a good place to start but if you really want to see what running at max pressure will do to the tire, try this - take a piece of chalk and draw a line about 2 inches wide across the tread from shoulder to shoulder. Now drive a couple of hundred yards straight ahead. If all of the chalk is evenly worn off you're good to go. But if the chalk in the center of the tread is worn more than at the edges of the tread you can expect the tire tread to soon follow not to mention greatly reducing wet traction since only the center of the tread is in any meaningful contact with the road.

Speaking of MAX tire pressures that you find on the sidewall, I found this:

A tire's maximum inflation pressure is the highest "cold" inflation pressure that the tire is designed to contain. However the tire's maximum inflation pressure should only be used when called for on the vehicle's tire placard or in the vehicle's owners manual. It is also important to remember that the vehicle's recommended tire inflation pressure is always to be measured and set when the tire is "cold." Cold conditions are defined as early in the morning before the day's ambient temperature, sun's radiant heat or the heat generated while driving have caused the tire pressure to temporarily increase.

For the reasons indicated above, It is also normal to experience "hot" tire pressures that are up to 5 to 6 psi above the tire's recommended "cold" pressure during the day if the vehicle is parked in the sun or has been extensively driven. Therefore, if the vehicle's recommended "cold" inflation pressures correspond with the tire's maximum inflation pressure, it will often appear that too much tire pressure is present. However, this extra "hot" tire pressure is temporary and should NOT be bled off to return the tire pressure to within the maximum inflation pressure value branded on the tire. If the "cold" tire pressure was correctly set initially, the temporary "hot" tire pressure will have returned to the tire's maximum inflation pressure when next measured in "cold" conditions.

A tire's "maximum inflation pressure" may be different than the assigned tire pressure used to rate the tire's "maximum load." For example, while a P-metric sized standard load tire's maximum load is rated at 35 psi, many P-metric sized standard load performance and touring tires are designed to contain up to 44 psi (and are branded on their sidewalls accordingly). This additional range of inflation pressure (in this case, between 36 and 44 psi) has been provided to accommodate any unique handling, high speed and/or rolling resistance requirements determined by the tire and vehicle manufacturers. These unique tire pressures will be identified on the vehicle placard or the vehicle's owner's manual.

Link to cite source: https://www.tirerack.com/tires/tiret...jsp?techid=196

My Goodyear Wrangler AT load range C say 50 psi. I think the Goodyear Wrangler SR-a p metric tire is only 44 psi

That's fine, we all can do as we please, but I must point out for the benefit of other readers the flaw in your logic. While overfilling the tires does lead to reduced roll it also puts less rubber on the road and reduces traction while increasing stopping distance in a panic stop which places all occupants at risk. At maximum pressure there is a greater risk of tire failure as the tire heats up because the PSI will rise right along with it. Lastly, the pennies saved in gas mileage is lost because the tires have to be replaced more often, so there is no financial benefit to over-inflated tires.

Agree and add: If the manufacturers could gain anything significant from specifying tires be run at maximum pressure without sacrificing something else important then they would do that to get ahead in the EPA fuel economy wars.