Tire Pressure?

[345CID]

What is everyone running for tire pressure? everyday driving? track?

[phillips2024]

runnin 40psi in my toyos.

[Northern Rider]

The factory settings of 30 psi are just too low for the 300C. The braking and cornering forces of this car will just roll the tire on to the sidewall at such a low pressure, causing very fast wear and reducing handling.

For me, 35-36 psi seems to be a good comprimise for everyday street and highway driving. If I go to a road course, I bump pressure up to 40 - 42 psi.

I have no idea where the drag racers like the pressure. Some of them should chime in.

[Mrnemo]

every day driving street mostly 36-39 seems fine. track ? no idea

[MM-JAPAN]

I was told by the dealer it's -10psi from the recommended tire company PSI MAX level, I have the NITTO NT 420 S at 40psi... Trying to switch my air tires to NITROGEN gas tires - same psi level (40).

[CaveMan]

I changed out tires from the stock size to 245/55/18. I had no idea what tire pressure to run after that. So I did some reading. What I came up with and made sense was tire temperature. The correct tire pressure, cold, gives us the best contact patch hot.


A few statements:

The temp of the tire inside edge, outside edge and center help determine tire pressure.

If the outside and the inside are hotter than the center the tire is under inflated.

If the tire is hotter in the center then the tire is over inflated.

If the tire is within a couple degrees on inside outside and center the tire pressure is correct.

The BEST way to measure the temps is to use a pyrometer with a prob.

A good IR pyrometer is fine for what most of us are doing, including me.

Rear tires will be hotter than the fronts, in most cases, because they are the drive wheels.

With that out of the way the test is simple. Take a SWAG (Scientific Wild Ass Guess) as to what you think the tire pressure should be. Check it and set it with cold tires, they've sat overnight. Go run the vehicle down the freeway for a good 20 minutes. No heavy breaking and don't throw it around. Just drive it like there is a cop on your ass.

Exit the freeway, get out and measure the temp on the tires. The outside edge, inside edge and center. If they're not within a couple of degrees note whether the edges are hotter or the center is hotter. The next morning drop or add pressure accordingly. Use 2lbs. increments and then repeat the process.

IF you take your cold temps when it’s say 65 outside and the next day it’s 75 then you’re tire will be roughly one pound heavier. But this is a different story.


Or…

Do short burns outs. The same rules apply for pressure based off of the pattern. If the outsides are darker than the inside your pressure is too low. If the center is darker than the outside then you’re running too high.

Taking the temp is more accurate and costs less rubber. A DECENT pyrometer will run around a $100. With a GOOD one running around $200. But it’s a tool and has other uses.

[stevesrt8]

Great post... Who sez a caveman can't do it?

We use the IR type for all kinds of tricks. Brought in a truck the other day that was missing on one cylinder, simply pointed the gun at it and told them which one it was. Diagnosis in 5 seconds!

A great dissertation on tire pressure.

Also note that SRT8 is factory recommended for 32 all around. I have experimented extensively and I recommend 34 for aggressive driving styles.