IRguy

The background: New forgeline GA-1R wheels, fits perfectly with new BFGoodrich G-force R1 tires 335/30 R18 rear and 265/35 R18 front. No rubbing at the front but upon initial install I had some steering vibration / shimmy like unbalancede wheel. rebalanced with road-force balancer, no change.
Took the car to a new track (Hastings, NE) - nice facility by the way - and I had a major tire/ wheel issue right away.
The car developed a noise coming from the left rear - especially during hard right hand cornering - which sound like something flapping in the wind, like a flat tire or like the wheel is coming loose. Of course no flat, tire holds preasure very well, wheel did not come loose, redid the whole wheel install torqued to 450pft, no sign of wear on hub or wheel, everything looks perfect. Next session, two laps, and the noise is back. kept coming out at mid sessions just to check and reassure myself that the wheel is on tight. Kept putting my head through the window to hear / locate it better.
Besides a very poor driving from me the whole day was ruined by this unexplained noise.
Any idea??

IRguy

Forgot to add, tire pressures (hot) 30psi front, 39psi rear
(Huge amount of marbles on every wheel and tires)
I went of track ones, not high speed no spin, the whole noise phenomena did not change.

tford

I had a similar issue a few months back at Thunderhill. I had switched to Brembo III brakes and was running Michelin Pilot Super Sports, that I had used in One Lap of America. I think my issue was related to the new brake pads that weren't bedded properly, but to be safe, I switched the tires back with new stock cup tires as well as fixing the brake pads. The issue went away. It was unnerving to say the least, felt like the tire was going to fall off. What was interesting in my case, was that if you turned the car off and on, the issue went away for a few laps and then the vibration would return. I think when the car senses the vibration, it goes into some sort of limp mode. I have HRE CL40 rims on the car. Not sure this helps, but good luck.

NJ-GT

Put stock tires and wheels, see if you have the issue. If negative, you have a problem with tire deformation or wheel defect. So, switch the rear wheels from sides, and check if the noise/vibration just went to the other side. If affirmative, then dismount rear tires and switch them from rear wheels, this is going to give you the answer of tire defect or wheel defect.

BBMGT3

I had a similar "flapping" sound, but from my front tires. My front wheel housing clip had come off and my tire was rubbing on the plastic covering in the corners. Not sure how it could happen to the rears, although at speed maybe the wind is blowing the housing onto the tires?

IRguy

No issue with stock tires on street driving, but have not "pusched" them since this issue came up. I wanted to revert to stock tires on the track but we have to leave and did not have enough time to experiment. I do not have the steering vibration that's for sure with the stock tires. The BFG-R1 experience this time was a let down. I liked them when I switched from regular PS2 to these on my M3. They provided much more grip, but the difference in grip compared to MPSC is not that much.
I will have the wheels checked out for flat spot. Even my steering vibration could be due to some flat spot on the tires.

About the brakes, I did not change pads at the rear recently. Just fluid a week ago to Endless 650. My front PCCB disck now has a faint line??!!! (one time I measured over 900F in the padock!!)

RollingArt

Perhaps you were driving off the racing line and in the heavy marbles where no one else goes. The noise could be all the debris hitting the bottom of your car. If you were going to wide in a right hand corner it would be your right side tires mostly in the marbles.

Driving out in the marbles can cause plenty of problems.





Phil

s4awd

Funny, I had the same thing happen to me on my mpsc's on my old GT3 (narrower tires) on the same tire as yours, the rear left. It started happening shortly after I had an instructor sit with me. Haven't tracked the RS yet so don't know if it will happen again. It was the same exact sound you described, kind of like a flapping or driving on a flat tire. The instructor heard it as well and told me to pit in but the tire pressures were fine and the tire looked ok. No issues driving normally either. Not sure it the sidewall had a problem and bends under load.

IRguy

I was very preoccupied with this noise throughout the whole day. I somehow doubt that the marbles are the culprit, mostly because it was just the rear left (other tires/wheels have just as much marbles) the sound is very regular, rhytmic, marbles would be more random I guess, and it came after two, maybe three laps. When cold, no sounds.
Other people in the car could hear it as well.

The Greek

I did a track event this weekend at Sebring, and have 18 GA3R Forgelines. Dont have any sound, but did notice there were wear marks on the inside wheel from the PCCB Caliper rubbing the inside barrel. Did you notice anything like that?

Nick

IRguy

No, I've got good (well at least OK) caliper clearence with the GA-1R. I think the wheels are OK, I really don't think my problem is due to the wheels. My guess right now is that my tires were stored for long, have some bad flat spots which is somehow accentuated by higher pressure. So during the first two lap no issue, then heat and preassure goes up and the flat spot declares itself. Just a theory...

kyrocks

If the noise is not there with your stock wheels and tires, then it is definitely your new wheels/tires. I wouldn't throw away the possibility that it is the wheels though. That must be some serious flat spotting to cause that...but possible

BTW, I miss you Iowa/Nebraska track guys now that I have moved. However, the track season in Texas is just a tad longer!!

Love your car.

IRguy

We missed you KY as well last weekend. This was my first track day since the flooding at MAM.
The only way to test the stock tire/wheel setup is to run them on the track. However last time when I had them on I did not have this issue at all. (different track and day)
I will try to take the wheels to a decent tire shop and see what they can figure out.