Brainz

Anyone in Houston have an extra set of rear wheels (with tires) I could borrow for a day or so?

Here's my situation: 2007 997TT with 52k miles on original suspension. I am not running spacers. I got new tires (MP4S) over Christmas and have since had them rebalanced three times. There's less than 500 miles on the tires at this point and they were road force balanced again just last week.

Unfortunately, I've got a "hula flutter" vibration in the rear of the car that starts around 90mph and appears strongest around 95mph. It seems to rhythmically cycle in position and intensity and it's really annoying/distracting. It is unchanged by acceleration/deceleration or changing gears/engine speeds. I have DSC and can dampen the feel of the vibration by running the firmer Sport setting, but it's still there. The vibration seems to lessen above 100, but the car doesn't feel as confidence inspiring as it should. Car feels great below 80mph.

It would be hugely useful to try a different set of known wheels/tires as that's still my main suspect, hence my request. Please send me a PM if you can assist.

Hopefully, if the vibration disappears with other wheels, then I've found the problem and can either try one more time to get them balanced right or can ask Michelin to send a replacement set of tires.

But if the vibration remains then I guess I've got to look elsewhere - - Other possible suspects include:

- axles/CVs
- rotors
- suspension joints/bushings?
- alignment? [not sure if/why an alignment would cause a vibration though]
- wheel bearings? [car runs quiet, seems unlikely]
- wheel studs? [seems unlikely, but maybe?]

Let me know if you have other suggestions for balance/vibration sources.

Thanks for the help.

ShatterPoints

Vibration could be control arm / bushing related, loose wheel, bad alignment, or a bad balance. I had a funny/ weird issue happen. When I bought the new tires and rims on my car now the shop which balanced my wheels did an AWFUL job. It was almost comical how bad it was. I went back and they admitted it was awful, so much in fact they suggested it might be a wheel is out of rounds from the manufacturer. While I was on the phone trying to sort out what they needed for me to RMA the wheel(s) the shop came back and told me OOPS... the cone on the wheel balance machine was warped or broken so it spun the wheel in a non circular motion which meant it would never balance. They repaired their balance machine and all was well after a 4 wheel re-balance.... Fun times...

Brainz

The last two balances have felt the same, which has me thinking my issue might not be the wheels/tires.

I have not had this car aligned and suspect it could benefit from one. In particular, I measured more rear toe in than is spec'd using cheap toe plates and tape measures. I forget the actual amount, but it was more than it should have been.

Could too much toe in and deep/fresh rubber treads setup a harmonic vibration?

bogey1

could just be a bad tire. It happens.

o7silverturbo

Find a shop that has a road force balance which can check the tire it self

Brainz

Based on my description, Tire Rack has offered to RMA the rear tires. I'll be getting new ones with RF balance on Friday. I'm very impressed with the Tire Rack customer service. Fingers crossed that all is bliss thereafter.

Dodaleca

Last spring when I took my car out of winter storage (in my own garage so I know nothing happened plus the car was sitting on flat spotter tire foam ramps) I got a terrible vibration as the vehicle speed went above "legal". In the previous driving season I had gone to similar or higher speeds without any noticeable vibration.

I took the car into the dealer and all four tire-wheel combos were found to be out of balance (one by up to a couple of ounces) - not sure why. However, after rebalancing all is good again.

Brainz

I've had the flat spotting issue on other cars in the past that sat for any length of time (usually months). It usually resolved after a good hard drive to warm up the tires. My current issue has persisted since new with multiple rebalancings and some longer drives to get things to settle. Hoping it was just a bad tire.

The new tires arrive today and get installed tomorrow. Tire Rack said they'd check the new tires for balance before they shipped them to me -- not 100% I believe them (only because the tires are delivered ~24 hours after ordering and that seems really fast) -- but maybe, and I truly appreciate the customer service. The new install shop is a well known BMW-affiliated race shop here in Houston, so I'm hoping there will be no doubt on the quality of the install/balance when done.

Dodaleca

My vibration was noted weeks after I had taken it out of winter storage and had done a lot of driving so I'm pretty sure it wasn't flat spots.

I don't know why the balance went so far off on all four wheels though - I'll see if it repeats within the next month when I get my car out of hibernation and back on the road (more than warm enough here but there's still a ton of winter gravel on the roads!).

Brainz

Got the tires mounted and road force balanced on Friday. The guy at the [high end BMW] shop assured me that all four wheels were spot on - - and I believe him as the shop has a very good reputation.

But in the process, he discovered that both outer front CV joints are slinging grease. I have yet to fully investigate, but I am hoping it's punctures and not torn boots, the difference being the amount of dirt that can get in to destroy the joint. The shop suggested that if I still had an imbalance to swap (not just reboot) the front axles. I can't help but wonder if one of the prior tire places stabbed the boots as retribution for having them reblance the wheels repeatedly as I'd almost certainly have seen or been told about the grease all over the insides of the front wheels. Lesson learned.

I got up early to do some runs in Mexico today. It was not a cool morning - - probably ~70 degrees, and the car had been sitting for almost 2 days. At first I was disappointed - - there was still a slight vibration ~95 - - nowhere as bad as it was, but it was there. It was cyclical and felt like it was in the rear as the sensation was through the car seat and not the wheel. But as the tires warmed up, it went away! I can only assume that MPS4s may be sensitive to flat spotting, especially when the tread is fresh?

Interesting datapoint for others, the rear tires got installed with 41psi on the dash, which usually reads a couple psi lower than my gauges at the tire valve. Once warm, they were up to 44psi per the dash - - much higher than I would normally run them (I typically target 39-40 hot, which is closer to 41/42 per my gauges). I do wonder if running them over inflated might help with flat spotting issues when fresh. Just a theory...

Anyway, I finished my test drive with a beautifully smooth ride. Much better. Now on to replacing the front boots (which looks to be a real PITA), or maybe both front axles, and then off to get the car aligned.

And for the Houstonians needing an alignment on any of your vegicles, go see Lee at Southwest Alignment on Richmond. He was recommend by the [good] shop that did my tires. I had Lee do my Cayenne yesterday - - he's good, really good. Tell him how you drive and how you want it setup and he'll do you right (or you can just tell him exactly what specs you want and he'll set that within the limits of your suspension). And the price is very reasonable.

jeebus31

Thanks for the recommendation - I went to Lee at southwest alignment today and he did an awesome job getting my turbo dialed in after all the work that’s been done. I am very happy with how it drives, he really did a great job.

Brainz

Yeah -- Lee is the man -- he really cares about getting it right. I had him do my 997TT last weekend. I ran into another guy that had a 997TT but was getting his SUV aligned while I was there. Good shop.

A418t81

There are threads with issues balancing PS4S on the RS3 forums. Quite a bit of them actually. Some have even had to RMA them. Glad you got it sorted.