I’m fairly certain it’s time for me to get my tires/wheels re-balanced on my '04 C4S as I’m getting a pretty good vibration at highway speeds, and I hear the howling noise coming from the rear tires that’s been described on other posts. I have Hankook tires with 11,000 miles on them, and they have plenty of tread left as I generally don’t drive the car hard (although I can see that the inside sections of both rear tires are wearing faster than the middle and outer sections as mentioned on many other posts, but even the inside sections still have ample tread left). There’s a local shop that I trust that has the Hunter GSP9700 “road force” balancing machine that’s highly recommended by Tire Rack, but one of the Porsche TSB’s regarding tires and wheels says “use only the Porsche center clamping set for balancing”. Does this mean I need to have this done at a Porsche dealer? Thanks in advance for your help.

 

Road force balancers work great. Porsche also sells water for your coolant tank, but I prefer to buy water from my supermarket.

If you are hearing howling you might be ready for a new set of tires, I would measure the thread depth.

Depending on the vibration, it could also be due for an alignment.

 

I use the dealer up in VT and they have that machine. I think it's about $100 for balancing, if they scratch or damage the rim I'm covered. Flemington or Princeton Porsche are good folks. I used them when I lived down in Jersey. You could save some mony if you take the wheels off and bring them there.