Based on some advise I got on the old Forum, I started with 1lb of pressure for each 100lbs of vehicle weight. Then I adjusted up and down until I found what worked best for me. We have 245/50R/16's and I've settled on 24psi in each tire.
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Ray has it: 1 psi for each 100 lb or 10 psi for each 1000 of car weight is a good starting point. I run 22 front 24 rear with Hoozier A6 tires on my Coupe got Auto-x and it has worked out for me so far. I know some guys who run as low as 18 psi for extra grip in Auto-x but for a street car I think 22-24 is a good place to start. You can go up or down from there but based on what I read keep the front and rears at no more then 2 psi difference.
I had never heard of 10 PSI/100 pounds before but if I had used that on my DRS it would require 8.5 PSI. That is about half of what I did run. But for standard size cars that seems about right. My wife’s 350Z weighs about 3500# and I do run about 35 PSI. That is a very good thing to remember, wait I had better right that down.
I think if I wanted to go to the effort to do a chalk test I would choose to make a spirited run through a nearby canyon and then check the tire temps which will give you a better picture of what the tire is doing dynamically. It would be interesting to do both tests back to back and compare the results. But for regular street driving the chalk test may be closer to what most people do most of the time. But both tests should be done when the tires are at normal operating temperature.
I know I will get some flak from this, but I have a few thousand miles running around 17 to 19 psi. Includes freeway and some sport driving. Great ride. 17" wheels. 245 front and 275 rear.
I'm running 245 18's front and 285 18's on the rear and keep the pressure at 18-18.5 lbs on all four corners. Heat across the tires are consistent. With a short sidewall you have to adjust the pressure until heat across the tire is even.
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