Discussion in 'The Garage' started by bigbadchev84, Jul 4, 2006.
what PSI should i run in my 39.5x18x15 that see mostly the street? i am currently running 20
Is there a max recommended pressure listed on the side of your tire?
I have asked similar questions as the last time I rotated my tires I aired them up right under what it says on the sidewall of the tire. I have since learned that the psi located on the sidewall is max inflation and in fact you should probably run what the stock tires ran because the gvw is similar. I was told to check the door panel (or glove box) and find the pressure that the stock tires ran at and to inflate to that same psi. Even though the tires are larger you can still air up to the same psi it will just take a greater volume of air to do so.
Correct me if I'm wrong guys.
my bro has 38.5x14.5x15 TSL SXs and runs 25-28, it says max 30, they flat spot bad if he doesnt keep them high, just be careful not to keep them high for a long time and go on a lot highway trips, u can end up ripping the little bands in the tires, which will make them bulb up in the middle of the tread and that just wouldnt be too friendly for ur tire....plus ull have much less traction.
Forget the sticker in the door jamb, you threw that out the window when you took the stock tires off. The rating on the sidewall is for MAX load applied. You don't have that much weight on them. What I've always done, which is a tad easier if the tires are new cause you can watch the nipples, is just make sure you're getting a flat contact patch. Every truck is going to be different because we all weigh in different. The actual tire is going to make a difference too. 20psi is probably pretty close. Just watch how the tires are wearing. If the are wearing a more in the middle, take a little out. If they are wearing more on the sides of the tread, put a little in.
In my old Toy, '95 ext. cab, sas, 35's, I ran 20psi because the truck didn't weigh enough to push the tire down for a good contact patch at anything higher. I ran this everywhere, city, highway, whatever. If I had a real heavy load that I was taking for a decent distance, I would air them up accordingly.
In the Blazer, with 350/465/205 on 36's, it weighs a little more to help "sqaush" them down and I think I have them at 22psi, but I haven't done a lot of driving to determine where they need to be. It may go up or down a couple psi.
edit: flat spotting isn't going to hurt anything, they'll smooth out in a few minutes of driving.
I agree with this, but take is a step futher. The tires temperature will tell you if it is running evenly across the tread. Go drive down a straight stretch of road for a while. When you stop, use a temp gun across the tread. Note the temps-outside/middle/inside. If it's hotter in the middle, for example-(125/140/125), take out some air. If it's is hotter on the edges,(140/125/140) add some air. Adjust them until they are as close as possible. One thing to watch for, if one edge is hotter than the other, (145/135/125) air pressure won't fix it. Possible your toe in is off, and the tires are scrubbing the outer edge, (or inner edge if they are toed out) or the camber is causing it and unless you're running IFS there's not much you can do.
Hope this makes sense.
do exaclty what the cold psi rating is on the tire, the tire manufacturers are expecting for you to use them like 39's are intended. the cold psi rating also compensates for the heating of the tire when used. use whats on teh tire even if you have no weight on them.
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