I've been doing a little poking around on the internet and some of the magazines' websites. Tire pressure is a huge thing. When I mean it's a huge thing, it's a huge thing. Look at the F1 drivers. .5 of a PSi is a win or lose situation.
After putting on the new wheels with the new Continental ContiExtremeContact tires (245/45/ZR17), I got to wondering what the tire pressure should be set at for a good ride and good handling all around. As with most cars that we drive, there's always a compromise between great handling and a great ride. Obviously a great ride would need the taller sidewalls and slightly wider tires. But at the opposite end, a great handling vehicle should have wider tires and a shorter sidewall.
This being said, I couldn't find anything that would tell me exactly what I needed for these tires. And, as an obvious information blurb, the tire pressure, if you're running stock wheels (or at least the stock size) and the same height of tires for your aftermarket wheels, they should be set at stock settings for normal daily driving. The manufacturer takes into account comfort, reliability, and gas mileage for this.
On the other hand, aftermarket wheels and different, smaller sidewall tires can have quite a difference in tire pressure from stock. From memory, my tire pressure should be at 28 PSi front and 26 PSi rear. This setting takes into account the stock 16" wheels, 215/55 R16 tire size. I, however, am running the 17" '99 Ford Mustang wheels an 245/45 ZR17 tires so tire pressure will be assumed to be different. After going through the calculations on the website I came up with the following tire pressures for front and rear: 32.5 front, 34.5 rear. This is not taking into account the smaller sidewalls, which is a major contributing factor. Too much give in the sidewalls of the tires can result in bent rims. This is yet another reason to have the proper amount of tire pressure all around.
I used my car's weight for the equation:
3070 (not including air conditioning, rear interior behind the seats, add my weight (whopping 135 pounds), extra carrying weight (tools, subwoofer, amp), and other miscellaneous things removed).
Divide the weight of the car by 100, this will give you the base pressure for the rear tires of about 30.7 PSi.
Add 2 PSi to the heavy end; 32.7 PSi.
For anyone running modified suspension add 2 PSi all around.
Therefore my tire pressure comes to 32.5 PSi front, and 34.5 PSi rear.
I can add more as necessary to insure that the wheels do not get bent out of shape.
Also note that tire pressure should never excede the recommended setting for the tires, the maximum pressure for your tires is posted on the sidewall of the tires. For many of us, the factory recommended settings are just perfect. Of course, increasing tire pressure with a performance oriented tire can increase the grip and the handling, vice versa for regular road tires.
Here's the link:
http://www.modified.com/tech/0208scc_ti ... index.html

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