johnwelch

I'm looking for either rims or rims and tires for autocrossing. 17x7.5 or 17x8 with at offset of at least 55 for the fronts and 17x9et55 for the rears. Blemishes are fine, but must be straight and true.

Tires should be 225/45 front and 255/40 rear.

arenared

When you say "at least" 55, do you mean numerically, for example 65, or do you need "at least" in terms of out from the body, for example, 45mm? Most people don't want to go inwards from stock. In my other post, I have 17x7.5ET52 and 17x9ET47 which is equivalent to using 3mm and 7mm spacers if that's what you want.

johnwelch

Good question. I am concerned about clearance to the front fender now that I have lowered my car. As I understand it, and I certainly could be wrong, going from a 7" rim to a 7.5 " rim would push the rim 0.25 " closer to the fender, IF I kept the same offset (55). Going to a larger offset would keep the outside edge of the rim in place, as it were. To compensate for the 0.25" shift I would need at least an offset of 60. Do I have this right? Or, is clearance to the fender on a lowered 993 not much of an issue?

arenared

You have the concept right. I can't speak for 993s, but just about every manufacturer is pretty conservative in keeping the tires from hitting the fenders. Also, the wheels camber in at the top during suspension compression or if your car is lowered. In addition to asking 993 owners, you could try jacking the car up stragetically under the control arm or driving one side up on a ramp, and then twist the wheel left/right. You might be able to make a guesstimate.

For Boxsters, the limit is actually the outside tire edge rubbing the plastic wheel well liner at full lock which is not a big deal. Also, keep in mind that a 225 tire will vary quite a lot across brands/models of tires. Check the specs on TireRack. You sort of have to look at both the tread width and section width to compare tires. The tread width won't change from increased wheel widths, but the section width will. A good rule of thumb is that the section width changes 40% of the difference from the measured rim width. For example. if a tire has an 8" section width measured on an 8" wheel, then the section width on a 9" wheel will be roughly 8.4". I've also find there is tire manufacturing tolerances of like +/- 1/8" between 2 identical tires.

With all that said, I can't see that your fitment is that close, however. There should be room to play, but check with some 993 owners or see what alternate wheels Porsche made for your car. For the 986/996 cars, Porsche makes a lot of different wheels with all slightly different widths and offsets although there are certainly a few more common sizes.

flash968

i have a set of immaculate C2 Turbo replicas that are that size with S0-3s on them, and painted center caps - give john at wheel enhancement a call to make sure they fit on your car though - ET on mine is 52 front and 47 rear - they are replicas fo ra C2, so i would think they would work - better check though