Slight "Wobble" on brake application

I'm getting a bit of a "wobble" when I initially apply the brakes. I feel it mostly in the steering wheel and it goes away once I'm on the brakes hard. It feels about like one "wobble" per wheel revolution. I've pulled the wheels and double checked the brakes and everything is tight. I guess it might be a warped rotor (I noticed this soon after a weekend DE at Road Atlanta), but I couldn't see anything wrong when I had the wheels off, but I'm not sure I'd be able to see a warp anyway...
Any other thoughs / suggestions.
Thanks

whens the last time you had your control arm bushings replaced?

Originally Posted by GrayGhost

I'm getting a bit of a "wobble" when I initially apply the brakes. I feel it mostly in the steering wheel and it goes away once I'm on the brakes hard. It feels about like one "wobble" per wheel revolution. I've pulled the wheels and double checked the brakes and everything is tight. I guess it might be a warped rotor (I noticed this soon after a weekend DE at Road Atlanta), but I couldn't see anything wrong when I had the wheels off, but I'm not sure I'd be able to see a warp anyway...
Any other thoughs / suggestions.
Thanks

Warped rotor is most likely, especially if you had been playing at Road Atlanta (I gotta get down there one of these days). By any chance, did you apply the hand brake after you tracked it? I've read that you should just leave it in gear and keep the parking brake off after you've heated the rotors up like that to prevent warping.

u got warped rotors or it can be ur Front control arm bushings...

Tie Rods. I had the exact problem and it went away after new tie rods.

Mine went away with new control arms and bushings

OK, sounds like most likely is either warped rotor, or control arm bushings...
I'm very careful about not applying the parking brake after track sessions, and am careful not to use the brakes to hold in one place, but I guess a warped rotor is possible anyway.
I didn't think of control arm bushings... Normally I would think that unlikely since I only have 36K miles on the car, but that includes about 8 or 9 DE weekends, so I guess it's possible..
Art... You're thinking of AMS (Atlanta Motor Speedway)... Road Atlanta is "up" from Atlanta, not "down"... RA is in Flowery Branch, not far from Gainesville and almost next door to Chateau Elan winery.

I have the same issue. The lower control arm bushing were dealer replaced last year and the front brakes were recently replaced. The only thing I can think to try would be cutting the rotors and see if it goes away.

If it were the rotors, would the wobble stay there through all braking and not just light braking?

Let us know what you figure out.

Originally Posted by bmpurdy

If it were the rotors, would the wobble stay there through all braking and not just light braking?

Probably depends on the severity of the warp. A slight warping on one of the rotors could be detected with light braking, but could be "smoothed out" as the pads apply more pressure. A severe warp (or multiple warped rotors) will be noticeable at any braking pressure.

Originally Posted by GrayGhost

Art... You're thinking of AMS (Atlanta Motor Speedway)... Road Atlanta is "up" from Atlanta, not "down"...

Heh...yeah, I realized my mistake right after I submitted the post, but decided that I could get away with saying "down there" as a generic catch-all. You're too observant.

If I were you, I'd bet on the suspension components as opposed to "warped" rotors. While it is possible that the rotors may be deformed by excessive, uneven torquing of the lugs, it's highly unlikely that it was caused by heat. I know that many are absolutely convinced that they've had warped rotors caused by excessive braking, and this will doubtless elicit many arguments, but I recommend reading the following written by the knowledgeable folks over at StopTech: The "Warped" Brake Disc and Other Myths of the Braking System it's pretty convincing and penned by brake guys.

Sounds like control arm bushings - tap the brakes repeatedly while leaning out of the window and looking at the front wheels (like your inching forward), you should see them going outward slightly when you hit the brakes. I had the same problem and resolved it with new control arm bushings. Word of advice ... upgrade to some better control arm bushings than factory and make sure the sleeve is included (that was a ***** to do). I have to do mine again (330xi) and it's only been about 6 months. I don't even drive hard!

my car used to wobble without touching the brakes, at highway speeds. turns out it was the front control arm bushings. why would his wheels wobble only when braking, and not while just cruising at highway speeds, if it's the bushings?

Actually, he said he feels it when initially hitting the brakes - but it goes away when hitting the brakes hard. Warped rotors would be felt throughout; light or hard. If the bushings are severely worn then they would be felt while at almost any speed. Mine are slighltly worn and can only really be felt upon light braking - 5 mph or less - or playing with the steering wheel back and forth. I don't feel it at high speeds (NYC streets) up to 80 mph - how fast are you going?

Resolved....

I took the car to my local indy shop today (Harrision Mororsports) and turns out we were "all" right.
There is a very slight warp to the right front rotor (which is the one I suspected). But the main problem is the CA Bushings are worn, although not real bad. If it were not for the slight rotor warp, I probably would not have noticed the bushing for some time. If it were not for the bushing allowing the wheel to more more than usual, I'd never have felt the effect of the rotor.
They replaced the bushings (I'll replace the rotors this weekend) and I can barely feel any effect form the rotor now... certainly not a problem any more.