Vibration through steering wheel with new tyres..

Recently bought a 996 C4 with GT pack (1999). Above 80 mph I noticed quite a bit of vibration through the steering wheel. Dropped into the local garage and got the fronts balanced (should have checked rears!), they balanced them up - no difference. Did 1500 miles around France in 4-5days, but kept it under 100 mph as something was definately wrong. Got back to the UK and took it in for the rears to be checked - the inside walls of both tyres were screwed. Two new PZEROs later and all seemed to be ok. However, still noticing some (albeit small) vibration above 90 mph even with the new tyres on. Am I just being paranoid here - or is there anything else I should be checking????

First, I would have an alignment done so that you know everything is right with the car. It will drive, handle better, and prevent premature tire wear. Second, I would have the tires balanced with a force balancing machine like the Hunter I'm attaching a link to. Don't know if this specific brand is available in the UK. But I highly recommend using this methodology. I just put four new Michelin Pilot Sport Ribs on mu '00 C4 and they are smooth from 0 to 110 mph. I have no affiliation with Hunter... http://www.hunter.com/pub/product/ba...159T/index.htm

ok - thanks, will give that a shot

Your wear on the rear tires is normal and a result of the aggresive negative camber setting by Porsche. Vibration is most often a result of improperly balanced tires. If you have no problems before the new tires, chances are the new ones need rebalancing again and again until they get it done properly. If vibration is more when tires are cold, you may have an out of round condition or flat spot. Many places do not have the proper equipment and/or cones to properly balance many kinds of wheels, but get close. If you want to verify the equipment is good or not, after they get it balanced, have them remove the wheel, turn it 180 degrees and then put it right back on the same machine. Does it still balance? Personally, I would go back to where I purchased the tires from and make them get it right or hire out to get it right. I would not waste any money on an alignment until cause of vibration is corrected.

I had the same problem when I bought my car - I had brand new tires all around. After three trips to get the tires balances and an alignment (all paid for by the dealer, thank goodness), the condition was improved but not completely eliminated. And all of my problems also started around 80mph, and showed up on some road surfaces more than others. Long story short, I had a rim that was no longer true. How did I find this out? I made the dealer swap rims and then we drove the car - problem was gone. This is the moment I also truly fell in love with my car and realized why I purchased a Porsche. The driving experience improved 300%.

come to think of it - I don't remember him balancing this new tyres once on.. he probably fitted them, then assumed they could go straight back on the car. I will pay him a visit. Vibration doesn't seem to be on cold more than warm.. do assumed that may rule out round conditions or flat spotting.

I guess first port of call would be the tyre dealer, then it they prove the tyres are 100% - on to either wheel alignment, or checking the rims. What's the process for having the rims checked out? and assume if they're gone it's likely to be an expensive exercise.... thanks

Proper balancing methods will eliminate rims as your problem IF balancing is sucessful Tire and rim are balanced together. If rim was bent or otherwise damaged where it affected balance, it will show up while balancing.