993Buyer

I developed vibration in the steering wheel while braking with my 1994 964 Turbo Look (C4), sometimes very pronounced.
I installed new front end (tie rods, shocks, etc) in the past and it drove fine...
But very recently I installed new rotors and pads and new tires were installed about 2 months ago.
Wheels were balanced and car was aligned at that time.

What could this be? Warped rotors, wrong brake pads?
Any pointers appreciated. Thx.

HenryPcar

Jack up your car until the wheel clears the ground. Spin the wheel, it will be tight due to the pads riding on the rotors, but if there is a spot that jams the rotors, then you know the rotor has a high spot due to warpage. Bear in mind if your rotors are not warped, there will still be some binding due to the pads touching the rotor. What you are looking for is a consistent binding, not a particular tight spot that jams your rotor. If you have that then the rotor is warped. Unfortunately you cannot turn a drilled rotor and the only option is to replace it. If it is new try to get n touch with the seller to see if they will stand behind it.

cjoenck

Other possibility is a failing wheel bearing. Any new noise, change in noise while turning? Any play in the wheel moving?

Bruni

Its time to replace your trailing arm bushings in front!

Frank 993 C4S

Did you bed your pads after you installed them? Also, you should avoid changing pads and rotors at the same time as it is really hard to bed the pads properly. I doubt your rotors are warped unless you took the car to the track or the German Autobahn.

Navaros911

I would check, in order:

1. Front tire wear pattern
2. Front wishbone bushings
3. Steering components (even as far as rack and steering column)
4. Brake rotors (check if they are true)

I've been where you are a few times. The issue has been, for me, point 2, point 3 and one time the tires themselves. The tires was simply a try to see if things got better, since everything else was checked and confirmed to be fine.

I had the rotors turned with the ProCut tool (I think that is the name) once and it made a little difference, but ultimately the tires fixed the problem. Went from Pirelli P Zero Rosso to Conti Extreme Contact DW in 2012 or so.

PAOLOP

Pads deposit on rotors

993Buyer

Those are some great pointers. Thanks. I will check this today and post what I find to be the culprit. Thanks!

Spyerx

Right, rotors really don't warp and I've had many times I come off the race track with brakes smoking, but they CAN get deposits.

Typical vibration check points:
rotor deposits
tire balance
tire issues
wheel bearings
control arm bushings
shock bushings
shocks

JasonAndreas

Are the rotors from Stoptech?

993Buyer

No, They're not Stop Tech rotors. Zimmerman, I believe.
Could the issue be caused by incorrect balanced wheels? It only happens under braking, so I guess not....

Navaros911

Sounds like control arm bushings to me.
Low tire pressure also contributes to this - a remarkable amount for me, with our wavy, tram lining tarmac at the lights.

Vandit

Yea. Check those front control arm bushings.

Illustration of what the control arm does with bad bushings.

http://www.jackals-forge.com/lotus/9...shbone_pry.wmv

Mark in Baltimore

+1 on pad deposits. Would get them from time to time with the race car. Pagid Oranges created the issue. Popping in a set of Hawk Blues (very abrasive) cleaned the rotors in a few miles.

Peteinjp

I’ve had the pad deposit issue as well. In my case I it occurred with new pads and rotors by holding the brakes while stopped while the were very hot. Causes a strong judder from then on when braking. Since then I always try to replace the pads on used rotors and make sure I don’t hold them while stopped without fully bedding them in. Some pads are more sensitive to this than others.

Pete