Hi all. Anyone know what are the correct tyre pressures for a set of 17” compomotives (they’re on my 85 GTS)? Cheers, Ray.
There's no set pressure. It depends upon the size/aspect ratio, side wall stiffness, and even compound. I'm sure Mike will chime in soon with what he runs. On a race car, you use a pyrometer to measure temperature across the tread face, taking into account suspension settings. You can fudge it a little on the street - start with a guesstimate pressure, say 33psi, and then take it for a spirited drive on a well know piece of twisty road. Then pull up, and place you hand across the tyre. If the edges are hotter than the middle, go up a few pounds. If the middle is hotter, let a pound or two out. When they're up to temp, and you've got the pressures in the sweet spot, you can feel the difference. Let the car cool down - a lot, like overnight, and measure the cold pressures.
On my car with 225/45R17 and 255/45R17 tires on Compomotive 17x8 front and 17x9 rear, I have run 32psi front and 36psi rear for 16 years. The 328 factory tires load ratings for the original tires were: 205/55VR16 (1250@33 psi) 225/50VR16 (1406@36 psi) To achieve about the same load ratings on my current tires, I use this (coincidentally, almost the same pressures): 225/45R17 (1250@32psi) 255/45R17 (1428@36psi) The tires are bigger, but so are the wheels, so the volume of air has not changed much. Pressure AND volume affect load rating. Aim for the same load rating as from the factory to start, and adjust from there.
Oh, OK. I must have been confusing you with someone else - who has the Koenig style road scraper on the front?
It filled out the wheel well better, and actually made the speedometer more accurate. Image Unavailable, Please Login
Image Unavailable, Please Login No, I do have the Koenig front spoiler. It used to have the regular front valance that I kept in my attic in case I decided to go for the stock look.
