Thread: tire pressure?
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Old 10-06-2018, 01:45 PM
Howard Jones Howard Jones is offline
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Join Date: Jul 2004
Location: New Braunfels, Tx
Cobra Make & Engine: GTD40, sbf 302 400hp
Posts: 38

I have about 25000 miles on my GTD. About half are track miles. Here's my tire pressure data for front 243.40.17 and rear 315.35.17.

I have camber set at F -.75 degrees, R -.5 degrees, Toe at 1/8" total front and 1/16" total rear.

On hot days at track >90-95F air temp start fronts at 26psi and rears at 25psi. Tires can be expected to pump up 3-5 psi. I think the cars feels best at 28 both. The cars goes to oversteer or understeer if pressure goes over 30psi at either end.

Under 80F air temp start tires +1 psi front and +2 psi rear with same pumped up target of 28psi.

Check after each run and adjust back to 28psi both.

Street cruse: tires will still pump up somewhat on a hot summer day but more like 1-2 psi over a couple of hours. If you are only going out in the morning for a hour or two start at 28 and it will be OK. Very hot days maybe try F-27 R-28.

As you can see when a lot of power is being used then the rear will pump up quite a bit whereas the fronts will pump up just a bit more when straight line highway drives over a few hours are on the agenda.

I have put both Continentals and Sumitomo summer only tires on this car and both seamed to like the same pressure.

Good luck with your new car and check those tire pressure a lot until you find what you like. You will be safe down to 24-25 psi but edge wear will go up at low pressures.
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