I just got my new tires and rims, and I am unsure of what psi to run. I have 325/60/18's. The guy that mounted them said he filled them to 50 psi. Am I crazy for thinking that is a little high? I have heard that 40 psi is a good number. Any advice on this issue? Thanks in advance!

 

It depends upon the load range. If the tire has a max psi of 50 and is a load range C use 40. LR D with a max of 65, use 45. LR E with a max of 80 use 50. Those are what I have used in the past with no wear or tire problems on an F150.

 

My tires are LR E, and the max psi on the sidewall is 65. Should I go with 45?

 

It's a matter of trial and error. 45 is a good start. If it feels rough on the street and it does'nt wear the edges or wafer the tread you can go down. I usually run a little higher in the front when nothings in the bed. And adjust when I know I'm going to put weight in.
But bottom line the tread will tell all. Alignment, pressure, ETC.
plus it does not hurt to have your thrust checked every year. That is the alignment of the rear in relation to the front. Ever see those trucks that looked like they were going sideways down the road? that's it.

 

45 should be fine. If you decide to go lower, I wouldn't go any lower than 40. However, I doubt that you will need to go lower. Also don't assume that if it rides a bit rough, it is due to too high a pressure. Those are LR E tires. The side wall is a good bit heavier than a LR C and does not flex as much.

 

Thanks for the replies. I think I am going to run them @ 45 for a week or two and observe what happens.

 

I have the Pirelli Scorpion 275/55R20 that came on the truck. The tire is labeled standard laod and has a max PSI of 44. what should I be running them at. Brought it home from the dealership with them at 44, took them down to 35 like the sticker in the door says. I am think 40, please advise.

Thanks.

 

I have 255/70R16 on my 97 and they are standard load with a max the same as you at 44psi. When I had the tires put on they were set at 35psi, I then bumped them up to 40psi and haven't noticed any weird tire wera in the 10k miles I put on them.

 

Thanks that is what I will run and monitor the tire wear.

 

Not a problem that's what this site is for, helping others.

 

What would be best is if you can search here and I think some have mentioned what Ford recommended for the 20" Pirellis. Each tire is different depending upon load range. Mine came with 18" LR C tires and the max is 50, recommended is 40. A p series tire with a max of 35 would probably have 35 as recommended.