steering vibration

[Torino]

I'm almost a 100% certain that all the problems you are relating to (vibration) is caused through the twomass-flywheel.
I had a Audi S3 (not sold in the US) with very similiar problems. Needless to say, it took Audi 3 times to solve the problem (after denying it first...). So that was a 3 time clutch out-clutch in job.
After the last replacement it finally felt like it should have been...

[ntmatter]

Another option, if you want a really perfect wheel and tire setup, is to get your tires shaved. Tires are not, as a general rule, perfectly round. When mounted on your wheel they'll be slightly out of true, so even on new and perfectly balanced tires you'll get a little vibration.

You can have your tires shaved, which is basically having them turned on a lathe after the tire is mounted to the wheel. This results in a perfectly round outer tire diameter, though it'll get messed up if you ever have the tire off the rim. I did this for a set of race tires once to get the tread depth right and it was like driving around on silk.

The other downside is that you're scraping off good tire until all everything is evened out, so this will significantly reduce tire life.

[socratic]

2001 Boxster here. The previous owner put on some new Kumhos before selling and I presumed they were balanced. But the car started vibrating at about 80mph.

I took it to a shop with a Hunter 9700 wheel balancer that does a "road-force balance"; that is, it applies a 1000 lb force to simulate the car on the road.

Let me describe the results this way: If the original state was 0% and a glass-smooth balance was 100%, then the job they did was like 80%. I still feel a bit of a vibration. I am now hearing through this thread and other places that Porsches are finicky. I will bring it back to them and ask them to check it again since it's only been a few days since I did the balance.

The place I went to also had a new machine (their Hunter 9700 was old they said). It is a machine called a "John Bean" and it looks "higher tech" using lasers to measure out of round wheels. But it did not have "road-force" and so I asked them to use the 9700. Maybe I'll ask them to use the John Bean as a '2nd opinion".

[socratic]

An update.

Went back to the tire shop. They double-checked both fronts with the Hunter 9700 and they both came out fine according to the Hunter.

One of the techs said that previously, the Hunter told him that one of the fronts was, and I can't remember the exact term, but it had a high spot. At that time, they did me a nice favor and popped off the tire and rotated it so that the high spot of the tire would match the lowest part of the rim. It still wasn't perfect but it was the best they could do.

Since the shop also had a new John Bean balancer, I asked them to use it to give me a "2nd opinion" wiith it. The John Bean did not have the "road-force" device. But it did have some sort of laser camera, 3 in fact, that helps determine if the wheel/tire is not "true" in any way. The John Bean confirmed that the balance was pretty much dead on, but with its cameras, it was able to tell the Tech that it was 0.25 off (I can't remember the unit, e.g. whether it was millimeters, inches, etc.)

The bottom line is that the tires are perfectly balanced but one of them is slightly not perfectly round. When asked if I should replace the tire, they said no, since there is some wear on the tires, a new one would have more tread and the steering would pull to one side. They recommended that since I don't do much high speed driving, that I suffer until the tires are worn and then get 2 new ones.

The next step, though I am not optimistic, is going to be a wheel alignment by a good shop. I've been told that alignments should be done every few years anyways. It's going to cost the equivalant of about $80 USD and I'm prepared to spend that to keep the car in good shape.

[Brucelee]

"It's going to cost the equivalant of about $80 USD and I'm prepared to spend that to keep the car in good shape."

Yes you should have an alignment and actually $80 is a very good price. Most shops charge well over $100 for exotics.

Make sure they have the right equipment and know how to do this job.

Good luck. :dance:

[limoncello]

Random thought - 77 mph. I feel slight but noticable transition when the spoiler comes up. The feel of the car changes a little, as does the sound pattern (very slightly but there). Shouldn't feel anything thru the steering wheel though.
Rear alignment at a local shop - $69.95. The local PCA folks use him and say he's very good. At that price (and given the rear tire cost) I think I'll put it on a as a regular interval item.