Captdigi

I have a 07 Boxster S and at highway speeds above 80, I get a subtle intermittent vibration. It comes and goes every two seconds or so. I don't feel it in the steering, and I had the rear tires balanced again. The tires are Hancook V12 Evos, and they are new.... Any ideas????

Byprodriver

Oh boy, here we go again! Let me guess, the original Michelins were great but they wore out & too expensive to replace so someone talked you into Hankooks!
No I'm not a mindreader or a jerk, just a tire enthusiast who feels like he has wasted alot of time trying to share his tire knowledge with others with little results. If you are interested in reviewing these past posts search this forum & 986forum.com . You have stated a somewhat unique issue since it starts above 80mph, so I will add that most OFFcar wheel & tire balancers spin at about 65mph so the tire is not really balanced much above 65mph. The problem is caused by the tire or the balancing so give the store you paid the chance to fix it.

Captdigi

Thanks for the "advice"...... BUT.... I bought the car from a dealer, with 24,000 miles on it, and the dealer put the new Hankooks on the car prior to listing it for sale.

Captdigi

BTW... I telephoned the tech. Department at The Tire Rack, as well as at Discount Tire here in AZ, and they both said that balance would not cause an intermittent vibration. This is why I entered this post.

Byprodriver

Wheel/tire vibrations vary with speed & road surfaces, is this a variable that can explain the intermittent nature? Sorry to reply as I did in my initial post, if you search this & other forums you will see how often Hankooks come up in conjuction with vibration issues.

Tinbit

My over 80 MPH vibration was caused by rear tires (Michelin) that were worn and cupped on the inside edge from the negative camber.

New tires and a roadforce balance cured the problem.

Macster

That the dealer put the Hankooks on the car means only the dealer didn't want to spend the extra money to put on N-rated tires. He pocketed the difference as profit. It does not mean the tires are worthy of being mounted on the car. Porsche does not recognize non N-rated tires for use on these cars.

Some possible causes of what you are reporting can be tire imbalance, wheel run out, alignment, and tire pressure.

(I hate to rain on your car purchase any more than I already have, but the dealer probably never bothered to align the car. I bought a used car with brand new N-rated tire and knew the alignment was out and took it to another dealer to have the car aligned. In fact, I bought a brand new Cayman S and within a few days of driving the car I knew the alignment was out and took it back to dealer and the service department aligned the car at no charge to me.)

Yet another cause can be a defective tire or tires in which the belts shift/move about. And another related to the tires is they being non N-rated have insufficient side wall strength.

Less common problems can be a motor mount or transmission mount failure.

You will have to engage in a process of elimination working with I guess the dealer (or your favorite indy) to determine which of the above are the cause of the symptom you report.

But before you do any of the above, buy yourself a good tire pressure gage and check the tire pressures cold and make sure the tires are not over are under inflated.

Sincerely,

Macster.