correct tire pressure??

[kwsmithphoto]

There's a bunch of ways to determine your ideal tire pressure, but unfortunately that's gonna change depending on what you're doing.

The way I do it whenever I change tire types or sizes is use 34/34 cold as a base line. 2 over door plaque in the rear to offset my rear stiffer rear sway bar a bit.

Then I run them fast on the freeway for at least 5 or 10 miles, like 75mph or more if traffic lets me.

Pull off the road and quickly check the now hot air pressure with a gauge and run a pyrometer across the tread. The pyrometer is more valuable for alignment but ultimately we're trying to get a sense of the contact patch while driving so it helps, but you can tell a lot just by hot pressure and looking at the tire over time to see how it's wearing.

Anyway, I just make sure that the pyrometer shows that heat is pretty consistent across the tread. If not, I adjust it as needed - up a pound or two if the center is significantly cooler than the corners of the tread, down a bit if the inverse is true.

Next check, after break in, is to run them in them quickly in the canyons and simply use pressure tests and the little triangle side markers that tell you exactly where the tread ends and the sidewalls begin. With experience I've found that a good tire, driven sensibly, will be in the low 40's in the front and high 30's on a warm (but not blazing hot) day is about right, as long as I'm getting close to the tire marks without going over. Add air if I am, remove it if I'm not.

For track setup, I use both tools and basically just try to get pretty much the same hot pressure from all 4 tires and using all of the tread but no more, and this is different for every track and changes throughout the day quite a bit. Being a FWD car it's normal for the fronts to run a lot hotter in all out driving conditions but the rear tires should be loaded well too, which usually means decreasing more air from the fronts than the rears before hitting the course.

Anyway, regardless of what you're doing, it's generally best just to get the contact patches pretty much equal and watch for wear patterns over time. Rotate every 5K and keep up on wheel alignment. Personally, since I often carry high loads around I expect the rears to be a bit warmer in the middle with just me in the car.

And of course this is largely subjective, especially for a daily driver. Most people want a nice combo setup to get decent ride quality, performance, and life out of the tires. Some people just want higher pressures on the road for sharper steering response, or less from the rear to help the car turn in at low speeds better, etc. And that's fine, but pressure gauges, pyrometers, and lap times don't lie.

BTW, that cold 34/34 baseline I start with? It's been just about always right for me with several different tires and sizes and load ratings. I just tweak it for track use or particular conditions.