gandalfthegray.

Would a set of 8.5 x 18 ET 47 and 11 x 18 ET 62 fit my 993 TT? I realize these are a 996 narrow body fitment, but as I understand all Ruf wheels are as well. It would just be a matter of proper spacers, correct?

I know you guys probably get sick of the noob questions all the time.

Nurburger

Fronts would be close if your car is low, but should work - 15-20mm spacer for the rear & they would fit. Tire width would be something to consider also.

gandalfthegray.

So if I understand correctly, the front would set in closer to the suspension? Perhaps a 5 mm spacer in the front would make it equivalent to the stock front wheel or does it not work that way?

Thanks much!

IamSMC

Use this Wheel Offset Calculator:
http://www.1010tires.com/WheelOffsetCalculator.asp

Results are given in "Inner Clearance" and "Outer Position"

V

Not to step on anyones foot here, but the rear wheels would actually fit even without a spacer. It would look weird though as the wheel would sit too far inward. I agree that a 20mm spacer would do the trick. A very good reference for wheel fitment is Bill Verburgs wheel offset page (in his signature). BOL.

gandalfthegray.

Thanks guys, I think I've got the ET thing figured out.

Is it a given then that if your offsets are correct that you will have proper brake clearance? I noticed in searching that the Boxsters have similar ET's as the 993 TT. Does this mean that I could fit Boxster wheels if I wanted to?

David in LA

No, you have it reversed....less ET for Porsche wheels means the center of the rim is closer to the fender, so a spacer would make it worse. For 993 TTs you can generally (note "generally") have an ET of 45-50 for the front and 40-45 for the rear with no clearance issues. Bill offset chart that was referenced above is a great summary of offsets that will work but also keep in mind there may be significant width variances amongst tire brands and camber settings will also affect clearance.

No, brake clearance is a function of the size of the brake calipers vs the size and design of the rim, which MAY then be affected by the offset depending on the rim design. So correct offsets is not a guarantee of brake clearance, especially if you are running Big Reds or Brembo HoGs. The offset determines fender clearance and clearance against suspension components on the inboard side. You can generally fit 18" Boxster wheels (although w/o spacers the rears will look funny) but the 17" wheels may not clear Big Reds.

dbf73

I know some 17's will clear Big Reds as I understand early 993tt owners used 17's because of limited 18 tire choices for track use at the time

gandalfthegray.

I really have no interest in 17's. I'm just trying to understand what wheels will work when I see a good deal on a used set.