UMP

I've got a 1989 C4 with 25,000 miles which I bought new. I put on Kineses 18" wheels, 8.5" in the front and 10" in the back, Eibach springs, cup sway bars and bilstein shocks. The thing tramlines like crazy, no fun to drive. I put the original shocks back on and it still darts back and forth. I figure the 18" wheel size is the problem. I know it's not the alignment because a good friend of mine who played crew chief for Audi at Daytona lined it up for me twice. So, any suggestions? If I go back to 16" wheels, any suggestions on a wheel type, size and tire size big enough to fill the wheel well?
Thanks.

adsc4s

It is the width and possibly the tread pattern of the tires. What type of tire are you running? On my previous 964 C2 Cab, I had 265/35/18 Pzero Assymetricos on a 18" wheel and tramlining was minimal.

UMP

adscab911... The tires are the Michelin Pilots they used put on the 97 model BMW M3's. I'll write down the tire size and get back with you tomorrow. So you think a simple swap of tires will still alow me to run the 18" wheels?
The fronts do look a little small for the rim size. They are stretched in a bunch. Remember, mine is a C4, maybe the 4 wheel drive system has something to do with the problem??

adsc4s

I have a 993 C4S with the same Pzeros on 18x8 and 18x11's with minimal tramlining. As long as you are staying pretty close to factory rolling diameters, the 4 wheel drive system shouldn't be the issue.

Let us know what the tire sizes are. They should be fairly close to a 225/40 in the front and 265/35 in the rear.

Also to clarify, by tramlining, I assume you mean the tires/car will want to follow patterns on the road. Darting back and forth could be a different issue ranging from bad alignment to wheel balance, worn bushings, etc. Your car is 4 wheel drive and even though your buddy is probably very qualified, I might still get it done by someone that knows 4 wheel drive Porsches.

UMP

I will get back with tire sizes soon, maybe I can run to the garage in a few minutes. I am very confident the car is aligned properly. Yes, it follows imperfections in the road and is very darty at highway speed turns on bumpy roads. At race track speeds, this all goes away with a massive push. I'm talking about street driving at normal cruise type speeds. If I were to push beyond apex at full throttle, powering out of a turn at 100%, no bump steer or darting occurs.

UMP

OK. Just got back from the garage. They are the Michelin Pilot tires. The fronts are 225-40-18 and they look STRETCHED on the wheel. I figure the wheels are probably 8" wide...maybe 8.5.
The rear is a 265-35-18 on a 10" wide wheel and fits square. I've been having to run 28psi in the front and 32 in back because it's so darty. The lower air pressure seems to help, but it's kinda low in the front.
THANKS !!

UMP

adscab911...I've also had people tell me that running 18" wheels on a 964 is not a good idea. Porsche does not approve this. The dealership would not even look at my car when they saw the wheels on it. The car has Carrera cup sway bars, racing dynamics front strut tower brace, stock struts, Eibach lowering springs (first stage progressive) and the 18" wheels. THIS IS DRIVING ME CRAZY

adsc4s

You are right, Porsche never approved 18's for the 964, except the Turbo. A 225/40 on a 8.5" would be stretched but fits nicely on an 8".

It could be a tire issue. If you are in SoCal, you can come by and try on my 18" wheel with Pzero Asymmetricos. At least that way, we could see if it is a tire issue or something else.

UMP

I'm in Cincinnati, Ohio. This could be a problem.
Since the 225 is stretched, my front wheel MUST be at least a 8.5". ****, I don't know what to do.

adsc4s

I am sure there are other Rennlisters in your area that would be accommodating. You could also ask on the Pelican Parts BB or at your local PCA.

That would be cheaper than just buying a new set of tires.

Good luck.

dove

Ive got a 90 964 cab thats been given the turbo body treatment,It has 17 inch turbo cup alloys, no tramlining the car drives a treat,it may be an idea to go for this size, the cars also been lowered so those alloys fit so well into the arch.
Paul

UMP

I'd rather not have to buy new wheels and tires if I don't have to. I'll try and post pictures tomorrow.

jchaley

I bet it is the tires (michelin pilots). I had these same tires in 17" on my 944 turbo. The tramming was so bad I was convinced something was broken or worn in the suspension (changed a bunch of parts and it made no difference). I changed the tires to dunlops and it drove fine.

john

Russ359

UMP,

Just to add a bit of info. I have 17" CUP wheels with the michelin pilots and the car handles great. Suspension is stock however. Car is a 1992 C2

Christer

I think in order to help UMP (?) I think it would be useful to get feedback from any 964 C4 owners only with 18" wheels. The owner with the 993 C4S, please check your offsets to ensure compatibility with the 964 otherwise that may be a waste of time (and cause damage potentially). The 964 C2 is also totally different so recommendations should not be given freely(or at least taken with a pinch of salt).

UMP, you need to be precise with your data. Is the front an 8.5inch or an 8? This could make a huge difference. What are your offsets? Did you have to use spacers, if so what size?

As the Jerry Maguire film says: 'Help us to help you'.