JeremyW964

Ok, I asked this question a few months ago - tonight I crawled into my attic to see the OZ Racing Wheel boxes that I have and to see if they tell me what the offsets are. The print on the side of the box is - Silver SV40 CM711S
Type 2305410911A Front 8.5J x 17H2 - ET56 I30 x5 Centerbore 71,56

Rear 9.5J x 17 H2 - ET56

I have a 1990 C2 Targa

Is the 56 the offset?

It's time for new tires - I have Yokos AVS i-40s and i-45's FR 17x215x45 RR 17x255x40

Can I put 225x40x17 and 275x35x17's?
Help!

Adrian

Dear Jeremy,
ET is the offset.
These wheels are a tad too wide for a 1990 C2 I think you will find. Seeing as the 1990 C2 came with 6Jx16 up front and 8Jx16 on the rear. I would say it would be guaranteed on a standard set C2 from 1990 that you will have major wheel rub problems that will require rectification.
However theonly way to sort this out is to install them and measure it all up. Some people have installed 225s on narrower wheels on the front. 5mm spacers are often used. 275s on the rear on 9.5Jx17 wheels, methinks not,
Ciao,
Adrian
911C4

Christer

Adrian

I have the standard Design 90 wheels on my car. The next time I need rears I want to go to 245/45/16's - will this be a problem?

Thanks in advance.

Adrian

Dear Christer,
Nope perfect fit.
What are you going to put on the front. You need to watch the 6% differential if you have a C4. By installing the 45s on the rear you are reducing the rolling diameter (increasing wheel speed). You would need to check that you do no exceed 6% from original (851 rotations per mile) and not be 6% different front to rear. Example, front 805 and rear 856. This will fail the pdas in a C4. Easy way to understand this is everything has to be within 50. 50 from original and 50 front to rear. I say 35 to allow for tread wear but that is just my way. Ignore if you have a C2,
Ciao,
Adrian
911C4

JeremyW964

Thanks Adrian!

Christer

C2 so will go with it - thanks Adrian.

MikeF

Tried some 8.5" wide wheels on the front of my 94 964 last year and the wheel itself rubbed slighty at full turn. Promptly removed them. So, 8.5 will likely be too wide on the front of your 90.

Question for Adrian, did Porsche change wheel well capacity in later 964's? I recently saw a late 964 with 10" wheels in the back with no rubbing! What gives?

Adrian

Dear Mike,
The only 964s delivered with 10 wide inch wheels on the rear, were the Turbo 3.6 and the Turbo S the RS 3.8 which was built on a Turbo chassis had 11 inch wide wheels.
There was a rear wheel arch capacity difference between the ROW Turbo 3.6 and the USA Turbo 3.6.
There is a rear wheel arch capacity difference between pre and post 1991 964 narrowbodies.
There is a front wheel arch capacity difference between a 1989 C4 and 1990 onwards C2s and C4s. There is a front wheel arch capacity difference between 964s with power steering and those without.
Ciao,
Adrian
911C4

Michael Witz

Since we're on this topic again..

I'm still shopping for my 17" wheels for my 89 C4 - probably my xmas present.

I'm not as worried about the front as I am the rear. Since it looks like 9" rears are more available (better deals).

I have done a fair amount of measuring and the rear wheel arch on my C4 seems very low. Like only 1/2 inch between the top of my 225/50 R16 tire and the bottom of the lip on the wheel well arch (and it's only inset about an inch)

How much travel is there? any opinions on how wide a tire can fit safely on the rear of the 89 and/or 90 C4's?

thanks

Adrian

Dear Michael,
On a correct offset (52, 52.3 or 55mm) 9JX17 wheel you can install fairly safely a 255/40ZR17. I am considering trying a 265 next summer. I am also seriously considering 225s onthe front but I will need to use a 5mm spacer either side for sure,
Ciao,
Adrian.
911C4

Michael Witz

Thanks Adrian -- or should I say the 964 Oracle

GP964

Hi there folks!!!

90 C2 Narrow body:
RUF wheels
fronts: 17x8.5 215/45/17

rears: 17x11 255/40/17

Thanks

JeremyW964

GP964 - You have 11" wheels on the rear that don't rub? What sort of offset? Do you have spacers?

I have 9.5 on the rear and it looks like I have about 1/2 an inch clearance on the inside rear... I do have the same tires, 215/45/17 fronts and 255/40/17 rears...

Michael Witz

Still measuring....

Based on previous posts I suppose I can be confident in purchasing the 9 inch rear wheels (right?) (assuming 50 or 52mm offest).

Looks like the 255 tires vary quite a bit in section width and tread width.

Is anyone running 255 Bridgestone S-03 Pole Position's on an 89 or 90 C4? Seems like they are the widest and tallest 255/40 R17's. And they also seem to have the best reviews on Tirerack.

thanks

JeremyW964

See the reviews in Tirerack.com

They rate the Kuhmo's well too.