Longdaddy

996TT, at speeds over 85-90mph there is a vibration in the steering wheel, that seems to get worse once I brake for the next corner. slower speed corners are fine. happened on 2 different tracks so I know it's not the surface

ruled out wheel/tire balance, checked the joints in the suspension best I could - everything felt tight. someone at the track suggested a warped rotor - does that make sense (why can't I feel it in lower speed braking zones?)

bobt993

check the wheel bearings and CV's

tsheehan

Pagid orange pads?

Regards
TSheehan

Sean F

a rotor problem is usually felt in the brake pedal not the steering wheel and you'll feel it each time you go to the brake.

To check the bearing, jack it up and see if there is any side to side play on the wheel

U4EEAH

http://www.stoptech.com/tech_info/wp_padremoval.shtml

Brake pad material transfer deposits on the rotor will cause a steering vibration more than a pedal pulsation, and can be felt without brake application, worsening when the brakes are applied, and much more apparent at high speeds. Most "warped rotor" diagnosis are actually pad deposit problems. The above Stop Tech link has much more info and solutions

kurt M

True but you will feel it at street speeds too.

weneversleep

I had this issue in my BMW E36 M3 track car. Running various Hawk brake compounds. Never noticed any kind of shimmy on the street, at any speed (well, within sane limits). But, once the brakes heated up on the track, the shimmy in the steering wheel started and just got worse as the brakes got hotter.

Cool everything down, and brakes were back to normal.

Turns out it was a combination of two things:

1. The caliper piston was slightly rusted and pitted. My theory was that as the brakes heated up, and the piston expanded slightly, it started binding up on the liner, because the surface of the piston was uneven. New calipers (cheaper than just new pistons and a rebuild kit, believe it or not) solved most of the issue.

2. Some vibration continued, however, After trying the various Hawk race compounds (HT-10, DTC), I switched to PFC 06 pads. From that point on, absolutely no shimmy or vibration. My theory was that my braking style just didn't suit the Hawks, and pad deposits were forming and then getting scrubbed away.

As has been said, a truly warped rotor is extremely rare. Much more common is pad deposits that then harden over time into high spots on the rotor.

Good luck.

996TT_STEVO

Possible Marbles picked up on Tires and inside wheels!!!

Jim Child

How did you rule out wheel/tire balance? If you throw another set of wheels and tires on the car does it change anything?

Land Jet

The same symptoms at high speed happened to me because of the tires creeping around the rims and going out of balance.

Longdaddy

no it does not. tried rebalancing track wheel and putting street wheels on - does not make any difference. this is most definitely not tires/wheels

BHP something or other.
I cannot see pad smear/hot spots, but I did not look on the inside surfaces yet.

Jim Child

I'm guessing its pad material transfer then. I'd try swapping in a set of new front rotors and a set of high quality, no compromise, race pads. I use Hawks, but you'll get lots of opinions on race pads. If it turns out not to be the rotors, then you can keep the old ones as spares.

I once cured a set of rotors that had major material transfer from Pagid Black pads, but I can't guarantee that my results would be repeatable. All it took was swapping in a set of Hawk Blues. After a few laps the vibration was gone, and the rotors were good as new. I never went back to Pagid after that, and have been running various Hawk compounds ever since with no problems.

Slippery slope

I just had the exact same problem for the first time last month: vibration in steering wheel that got progresively worse throughout the track day, and worst when 1) higher speeds, and 2) braking.

I had Pagid Oranges on, and there were smear marks around the cross drill holes of the rotors, and holes full of pad residue as well. I switched to street pads the next day, and the problem went away.

Next track day, I tried the Pagid Oranges again, but this time checked and cleared the rotor holesa couple of times during the day. Everything fine, vibration gone.

Hope your problem has an easy fix as well,

Rob

Z-man

+1 on the wheel bearings. Is the vibration more if turing one way or another?

To check if a wheel bearing is going in the front -- jackup the front of the car. place a finger on the spring (as long as it isn't a coil-over spring that's loose around the shock when the car is off the wheels), and rotate the tire. If you feel vibration on the spring, then you have an issue with the wheel bearing.

-Z