silvester_2000

Just bought a 964 and it came with a spare set of Cup 1 wheels from a Cup Car! I need suggestions for:
1) F/R tire dimension (F: 255/40/17?; R: 275/35/17?)
2) Tires (hard to find max perf summer tires for 17's).
3) Spacer width for rear (Cup Car 68mm v. standard 52mm)

I have combed through past post and can't find recos for this unique set of wheels (9.5" rear with 68mm ET) for my narrow body C2.

Cup Car Cup1 wheel dimensions:
F: 17 X 8 (ET 52mm)
R: 17 X 9.5 (ET 68mm)

my first post here ever, so would really appreciate the help.

HalV

I'm sure there are others on that can give you more accurate info but I'll do my best. You'll probably want to go with 225/45 in the front. In some tires you might be able to push it to 235s but you might hit the inner fender wall. You could try to space out the fronts 5-7 mm. On the rears you'll probably want ~20mm spacers. You could try 275/35s as I've seen a number of people run them. I run the spec 255/40s. Good luck and let us know what you end up with.

u7t2p7

The OP has 7.5" fronts and 9.5" rears. I think you are referencing standard Cup 1's 7" front and 8" rears with respect to your suggestions. Also where did you come up with 18's in your reply? 235/275 should be fine with those wheels.

Super90

As I read it, the OP has 8" fronts and 9.5" rears. I'm running that setup on my Cup 1's.

I bought a set of Michelin Pilot Sports about a year ago. 225/45/17 and 255/40/17. I was told at the time that Michelin was discontinuing one of those sizes in that tire and, consequently, the fellow did me a huge favor and gave me a substantial discount. This was at a very specific Discount Tire shop that does lots of work for the local SCCA crowd.

Evidently, the tires available in that sizing combination are limited.

Bill Verburg

The 964 Cup cars originally came w/ 8ET52 & 9.5ET68 x17 w/ 235/45 & 255/40 x17 Tires(Toyo F1-SR) The rear used a 21mm spacer(the spacer came on several different models w/ varying pricing & part #s for the same parts, cheapest used to be 477.501.701 x2 from 944 & some Audis), longer studs are needed w/ these spacers 911.331.671.00 x10

The lips and oil lines need to be massaged for clearance

later versions of this car came w/ 8ET52 & 9.5ET68 x18 same spacers and studs, tires 235/40 & 26535 x18

tires as large as 245/40 and 275/35 x17 have been fitted w/ some additional work involved, usually running quite a bit of camber as well.

silvester_2000

Great info Bill and Super90. very helpful. questions for both of you...

Bill, given the optional Cup 1 rears are ET52, shouldn't I be able to use a 17mm spacer to get an effective offset of 52 instead of running a 21mm on the ET68?

Super90, can you share photos of how those tires (225/255) look on your 8/9.5" Cup 1's?

BTW, here's a shot of the car now with 18s. some changes underway...

HalV

Good catch on the "18s". I meant to say "fronts". The rest of my suggestions stand!

Bill Verburg

street Cup1 rears are 9x17ET55
front space is 72mm
back space is 182mm

Cup rears w/ 21mm spacer 9.5x17 ET47(68-21)
front space is 86.5
back space is 180.35

Cup rears w/17mm spacer 9.5x17 ET51(68-17)
front space is 82.35
back space is 184.35

The difference between using a 17 or 21mm spacer is where the extra room is, want room at the lip, use 17mm, want room inboard at the oil line, use 21mm

hockenheimr

About to buy some tires for my rep Cup1s (7.5 fronts, and 9 rears).

This will be a street car, what do you guys think will be the max sizes I could run without too much camber?