revolution993

Cup wheels 8 and 9.5 with 21mm 😍

RSA964993

I have the original Cup wheels from my RS America so I can move the rears to the front and I’m interested in the 9.5 x 17 for the rear that’s being discussed here. I looked at Sun Coast parts and they offer the 9.5 x 17 and also a 9 x 17 Cup wheel. I haven’t seen anything mentioned about the 9” fit for the rear instead of the 9.5” for the rear. Will that rim achieve the same look? If I understand correctly the 9.5 will require changing out the stock studs for longer ones and have to use spacers. I’m curious if the 9” can be used without spacers and longer studs but achieve the same look in the back. By look I’m referencing the great pictures above, they fill out the wheel well nicely. Thanks.

Jbarnes RS

I run them on this car.

Vandit

The 9" Cup wheel is probably a +55 offset versus the effective offset of +47 on the 9.5 with the specified 21mm spacer (+68 less 21 = +47). Plus, the 9.5 wheel will be wider by .25 on each side which is approx 6.4mm per side. So knowing all that, running the 9" wheel (which bolts up and fits without any further spacers or modifications) will mean your rear wheel will be 14.4mm further inward, which is slightly more than half an inch (.57in), than the 9.5" setup.

tjb616

Correct. And if you want to use a spacer to move the 9" wheel out, you're going to need to replace the studs anyway, so you might as well go with the 9.5" Cup wheel and Porsche Motorsports Spacer designed for the car. The studs can be replaced without removing the hub, not too difficult.

GeorgeRSA

Thank you for the responses and guidance guys - appreciated.
Having the 9.5 wheel sounds great, with all the associated spacer and stud requirements - and next question is tire size...
I plan to run 255/40's, but don't like the 'stretched' tire look in general - any pictures of this tire size on the 9.5 rim for visual reference?

tjb616

Post number 15 in this thread shows 255's on the 9.5 Cup wheel. You might prefer a 265, the Cup car OEM size, or even a 275. But it also depends on the tire profile. Different tires have different shoulder shapes which contribute to this look.

GeorgeRSA

265 with a 40 profile?

Bill Verburg

The original 964 Cup tire sizes w/ the 8 & 9.5 x17 wheels was 235/45 & 255/40, by '92 there was also an 18" option also 8 & 9.5 which would have used 235/40 & 265/35

Bill Verburg

Here's a comparison of the 8/9 vs 8/9.5 w/ the same tires

2000m2

Slightly off topic, but I've been wondering why the RS America came with 7" & 8" front/rear from the factory?

GeorgeRSA

Good question. Would have been nice to follow the 8 & 9, or 8 & 9.5 set up.

RSA964993

Thanks everyone, very helpful!

Cupcar

Just to add in here what the factory suggested for fitment on the Cup cars and 964 Turbo for 9.5" Cup wheels.

For 964 Cup A 21 mm spacer part number 477 501 701 was used in the rear along with longer studs pressed in to hub part number 911 331 671 00.
https://www.sunsetporscheparts.com/o...acer-477501701
https://www.sunsetporscheparts.com/o...c=YT1wb3JzY2hl

For 964 Turbo a spacer part number 951 331 611 02 along with 45 mm wheel studs 904 341 671 00 pressed into the spacer was bolted to the existing studs on the hub.
https://www.sunsetporscheparts.com/o...er-95133161102
https://www.sunsetporscheparts.com/o...93-90434167100

H&R makes similar spacers to the Turbo for much le$$

RSA964993

So tire sizes.... I’m up to 4 post it notes doing research on this and figure I’ll just ask the experts here on the ideal set up. The car is a RS America and I’m moving the rear Cup One wheels (965 362 126 01) (8” x 17” ET 52) to the front. It should be noted that I’m running 993 Big Red Turbo brakes up front. I’m going to get some 9.5” x 17” ET 68 Cup Ones (965 362 128 05) for the rear.

The car is being restored and is retired from racing so it’ll be a driver and not tracked but I’m positive it’ll be driven hard at times. The fenders are either cut or rolled so the fender lip isn’t an issue, Camber has been set to negative 1.6/1.7.

I’m a fan of Michelin tires and am thinking a summer max performance tire would be ideal. I say this because I’ve looked up tire sizes and some of the ones I looked up there were very few selections.

So what is the best tire size? I’m looking for that great Cup One look that fills out the wheel wells and works for what I mentioned above. Very much appreciate the best set up suggestions because I’m on the hunt for the rear rims and will need to get tires. Thanks!