Michael Witz

Hi all,

I have a new baby (its an 89 red C4).. I want to put on 17 inch wheels for looks and auto-cross.

I've read previous posts and know I'll need to install steering stops in the front, etc..

Based on what I've read so far I'm leaning toward 7 inch rims in the front and 8.5 in the rear (Boxter wheels).. http://wheelenhancement.com/98699617.htm

Questions:

Anyone have experience with these wheels on a pre-91 964

If I can get 55mm offsets front and rear will I have sufficient clearance with 205's in the front and 255's in the rear?

The tires I’m thinking about have section widths of 10.4 and 8.4 (Rear/front).. would these widths present any other clearance problems?
http://www.tirerack.com/tires/Spec.j...+Pole+Position

Thanks a bunch,

- Michael

MelissaM

Michael,

I just happen to have the 17" Boxster wheels on my '90 C2, with the Bridgestone SO-3's. 205/50/17 in the front, 255/40/17 in the back. They fit my C2 just fine.

Hope this helps!

-- Melissa

MelissaM

I just checked the wheels on my car, and wanted to clarify something:

rear's: width = 8.5", offset = 50
front's: width = 7", offset = 55

As I mentioned before, I've had these wheels on my car for the past year and a half, and I haven't had any problems with clearance.

-- Melissa

PS Michael, congratulations on your new car! Enjoy it! (Sounds like you will if you're already planning on autocrossing it.)

Adrian

Dear Michael,
Instead of using or installing steering stops you can also use 5mm spacers onthe front. You do not need longer studs.
The 1989 C4 has a different design front wheel arch asembly as compared to the 1990 models and wheel rub is an issue.
Personally I would stick to 16 inch wheels for autocross.
I use 911 (964) Turbo wheels. You also need to know about the 6% differential rule for the Traction Control. You must keep the rolling diameter all around and back to front within 6% of original. The original being 205/55ZR16 front and 225/50ZR16 rear.
You can check the specs at tire rack.
However you mst keep your offsets on the new wheels to 52.3mm, 52mm or 55mm front and rear. You 964 has an offset of 52.3mm and the original 16 inch wheels Design 90 were 52.3mm offset. These wheels are also very light and great for autocross,
Ciao,
Adrian
911C4

Michael Witz

Thanks a bunch for the info -- looks like this should be pretty straight forward..

no steering stops :-) yea!!

the rolling dia on the 16's is 837 rev/mile.. the 17's will be 830rev/mile (front and back).. So this should be perfect

Michael Witz

Adrian -- One clarification needed..

"However you must keep your offsets on the new wheels to 52.3mm, 52mm or 55mm front and rear."

with these wheels, if I put 5mm spacer on the front my offset will be 50mm.. and will have 50mm offset on rear w/o spacer..

Any issues with this??

thanks

Adrian

Dear Michael,
No issues at all. If you keep the "new" wheels to the original offsets the 5mm spacers will just move the wheel a little way further out. You could use 47mm offset wheels and achieve the same. Pity Porsche do not make one. RUF did in the old days I believe and so did Techart.
Ciao,
Adrian
911C4

Michael Witz

Once again -- thanks a bunch

Drew_K

Michael, here's an idea: keep your old wheels (16 inch I assume) and put some track tires on them for autocrossing. I bought some new 17 inch rims for everyday driving and put some R compound tires (Toyo RA1) on my old 16 inch rims. The R compound tires make a HUGE performance difference, and they're street legal so you can drive them to and from the autocross.

Only downsides are additional expense for the track tires and you have to tire swap for each autocross.

Just an idea
Drew 92 C2

Michael Witz

I was thinking about using DOT legal track tires on the 16" wheels given Adrian's comments on the stock design 90 wheels I already have..

thanks