Thread: tire PSI

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Just put four new tires on my roadster. Mickey Thompson ET Street SS P295/65R15 on 15x8.5 rims rear and Coker 56047 Firestone F560 Radial Tire-155R15 front on 15x4.5 rims. What do you think a good starting point for psi is?

I'm running ~24psig rear, 26psig front on mine with P285/70R15's & the same fronts you're running. I did the chalk check for the rears, using kid's driveway chalk to put a heavy mark across the tread, drive 50' on asphalt and stop to see how much is worn away. Started at 30psig, dropping a pound at a time before it wiped the whole width pretty even at 24psig. Fronts are pretty narrow, so I just bumped them to 26. Getting an even wipe shows you an ideal contact patch - best for grip, for longest wear, and more comfort, too. It's an old Jeep trick, running big meat with light weight, and trying not to wear the big, expensive tires out in the middle by running "recommended" pressures for trucks.

Thanks Roger. Used to do the same thing with liquid white sneaker paint for bracket cars at the drag strip to find optimum pressure. Paint 'em, let it dry and do a burnout. Also allows you to tell if you have equal weight on the rears, left to right, or whether you need to make some chassis adjustments.

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Yeah, I'll end up doing the chalk test. Every time I put custom tires an a car/truck I do. I just wanted a good starting point. I'm at plus two pounds front and rear of where you are at Roger, so I guess I already had my good starting point.

Now I just need some decent weather. It snowed the last two days in Colorado Springs. Jeez I'm sick of winter!

Thanks for the replies...


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You're in the springs?

Small world. I was stationed there 09-12

Originally Posted by firebird77clone

You're in the springs? Small world. I was stationed there 09-12

Yep. Lived here since '64 except '82-'85 when I was stationed in Germany.


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