paver

Car had 5000 miles on it when I bought it. OEM Pirelli Corsa were still on it but the rears were almost gone. At about 85 mph I could feel a moderate but noticeable shimmy in the steering wheel. More noticeable under firm braking.
I decide to go ahead with new tires. Had the local dealer mount RE-11's all way round. Told him of the problem. Picked the car up and they said it just needed a proper road force balance and all is good. It felt much better but not totally perfect. Now after about 150 miles on the new tires it's gotten worse. Not necessarily feeling in under braking like the first time. And I can speed up to get it to stop the shaking.
Any thoughts?

TRAKCAR

hmm, you do feel evrrything in the wheel. I rarely have 4 perfectly balanced tires for long..

LehmanZ06

Maybe a slightly bent wheel ??

997gt3north

Go to a different shop and have them re-check the balance of each wheel.

The following is a true story.
- local shop could source me reasonably price tires
- went to them for other car
- went to them for a set for the gt3 + to mount some winters
- got big wobble
- went back they redid them
- still had shimmy
- season ended - put on winters (last year for drive to keep car alive) - car had shimmy
- take back they redo
- just accept it move on
- get new set in spring PSS - got shimmy
- decide to go back to my race shop to tripple check
- tires go on their new machines
- they look at me and say - who they **** balanced these?
- they were so far off according to their machine
- in fact, just removing other shops weights made it better
- they re-balance
- same PSS tires are Perfect - absolutely Zero vibration

It is worth a try - I couldn't believe it but I saw both shops do it right in front of my eyes.

paver

Yep, just in the steering wheel. When you get out of balance do you have what I'm describing?

"Maybe a slightly bent wheel ??" I don't know. Pothole maybe? It's only got a couple of trackdays on it.

Thanks. Wish I had a race shop close. I think the nearest one is 250 miles away over in Atlanta. As far as I know, the only folks even remotely close to me who can deal with the CL's is the dealer. I do have the breaker bar and torque wrench. May be time for me to learn how to use it.

NJ-GT

I had horrible vibration on my RE-11 after two sessions at Daytona, I thought I killed them by running them at higher speeds than their speed rating: 168mph. Tires were balanced at my local GY shop, same as my super strong race wheels and MPSC. MPSC vibrated a little but not too bad.

I re-balanced the RE-11 at Daytona and placed tape on the wheel weights. I mounted my RE-11 this past weekend, and now the car drives better than all my daily drivers. My RE-11 are almost 2 years old, running on -4.2/-3.5 degrees camber, track days, autocrosses, drag races, and they feel smooth once again.

Now, I just have to find a shop with a good balancing equipment. All this time blaming my stiff springs for all the vibration, and it was just a messy tire balancing machine.

Florida is motorsports desolation and abandonment compared to all the quality race shops and tire shops in California.

ATL Fahrer

Try reaching out to the local PCA chapter in Huntsville. There are some pretty knowledgeable guys there that may be able to turn you on local Porsche wrenches.

Is the car CPO'd?

Forgeline

If you can speed up and make it go away, it is almost always a balance problem.

Ducati5150

Had a similar issue with an 07 CPO'd - both front and rear passenger rims were bent - balancing helped but the problem wasn't solved until new wheels were fitted.

drl

Anybody use race tape over wheel balance weights?

TRAKCAR

Always tripple tape.

paver

I think north Alabama has that beat... motorsports desolation here is probably lunar.

Not CPO'd, bought direct from PO

Thanks. BTW, saw a beautiful set of one piece forged CCW's on a ZR-1 at Barber last Saturday.

I guess the only thing that gives hope that it's not the wheels is that it just isn't nearly as bad as it was before I got the new tires. The fact that there was improvement would seem to rule out the wheels. Today, it felt really minor...just annoying that it isn't perfect.

Turn3 Autosport

Be there when your tech mount the wheel/tire on the balancer. Watch closely as the wheel spins. You are looking for a radial or axial movement. You can watch both the tire and the wheel. You likely will see something as nothing is perfectly true and the human eye can detect down to about 2 thou of movement. However, it should give you and idea of where the issue is, tire or wheel. A fairly large runout can still be hidden by a good balance....

Cheers

paver

Thanks for the info!

paver

David/Forgeline, my apologies. I guess if you read my response to your response, you probably think I'm an idiot...and rightfully so. I didn't see a set of CCW's on a ZR-1. What I think I saw was a beautiful set of GA-1R's...the senior moments are coming more often these days.