Thread: tire pressure??????

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I got some yokohoma es100's for my truck. It has 225/45 r17's in front and 235/45 r17's in back.

My problem is summit can't tell me what the optimum pressure would be, they said "call Yokohoma."
Yokohoma won't tell me for liability reasons because my truck is modified. They wouldn't even let me make suggestions and tell me if I was in the ballpark.

The tires read 50 psi max on the side, but I have NO IDEA what I should run them at. For all I know it could be 32 or it could be 44.

Does anyone have suggestions. . . . .I swear I won't sue you if you are wrong.

oh yeah, it's got an iron bb in the front. The gas tank is in the rear.

The max rating - as you apparently know - is for max load.
A lot of people see 35# on the tire and pressurize it to that point.
Making in some instances a rough riding car.

When I bought my 88 Mustang GT with 5.0 liter etc. new, it rode like a friggin tank.
I figured it was the semi race-o type suspension, but all it was, was too much pressure.
The dealer popped 35# into the tire and a couple of days after I picked up the car I found the 30# recommended sticker on the passenger side door frame.
After running the pressures down to 30#, the car rode a lot better and handling was fine.

I run 30# front and 20# rear tire pressures in my fairly lightweight 32 roadster.
Handling is fine, the tires run cool on the highway on hot summer days and the ride is ok considering the old style suspension.
(The rear tire is a 285/70R-15 designed for a 4000# + car.)

Here's an easy way to get your pressures set up initially.
Air up the tires until they look right.
Water down a cement driveway.
Roll the car into the water - either end one end at a time - roll it out onto the dry pavement and take note of the pattern the tires leave behind.
Best seen after the initial roll-out where the pattern is too wet and before it dries out too much.

Dark in the middle, light on the sides, too much pressure.
Light in the middle, dark on the sides, not enough pressure.

Check tire temps by running ten miles or more at highway speeds.
You should be able to hold your hand - palm down - against the tire sidewall without having to remove it.
Or at the least, if it's a really hot day, you can touch the tire for a reasonable period of time.
It the tire is hot - and some experience will have to be gained - you won't be able to hold your hand on it very long.

I'm guessing that with the low profiles you're running, you're going to be fairly close to the max pressures for the correct wet pattern.

This same technique works for an initial drag racing setup.
Do a short burnout, check the pattern.
You may find that with equal pressures the patterns will not match.
That has to do with the dynamics of chassis loading on launch.

The burnout bit, works especially well on cars with an open diff.
Sometimes you can do a little weight jacking to get more load on the right rear and other times a minimal pressure adjustement will do it.

YMMV, but this works for me.

thanks, I'll test it with some water.
I think I have them at 35 now, maybe I should go a little higher.

Saw this tip recently, set the pressure, make a mark with chalk across the tread, go drive it. Once you reach optimum pressure, no chalk left after the drive. Made sense to me. joe

I was thinking of doing that with paint. I wouldn't imagine chalk would last more than a few hundred yards at most.

I would think you would warm up tire, mark it, drive it, and inspect it. Won't need to go far will you?

good point.
I guess I may as well wait to get it aligned before doing it anyhow.