E46 Steering Wheel Shimmy

My E46 (02 330xi) has a shimmy in the steering wheel. It is most noticable after I heat up the rotors. And if I heat them up a BUNCH, the shimmy is VERY noticable, almost to the point of wobble. After a
couple of 80 mph down to 20 mph braking sessions (and yes, I checked my mirrors), the rotors are almost smoking.
My guess is that I have warped rotors and they need to be replaced. I have drilled Zimmerman rotors on the car and they're a little over a year old so I didn't expect them to warp so soon (or at all, for that matter, but hey, stuff happens).
Any ideas of what could cause the shimmy problem besides warped rotors?
Does something else heat up after some serious braking that would cause the shimmy? Something besides rotors?
Hopefully it turns out to be some type of $5 bushing or something cheap, but I bet I'm buying new rotors.
Thanks for any advice.
Tom
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Tom wrote:

Definitely the rotors. Skip the fancy cross-drilling next time and you will be much more satisfied, plus they are less expensive. Zimmermans are OK, but the cross drilled ones do have a tendency to warp.
-- -Fred W
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Malt_Hound wrote:

I swapped out my front rotors yesterday.....problem gone. It was the rotors, nothing else.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hopefully you used a torque wrench when tightening the wheel bolts. Too tight bolts can also warp the rotors over time.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
joe_tide wrote:

Good advice, about the torque wrench. But I must admit that I have been pondering this oft quoted pice of advice. Why should the rotors warp if the wheel bolts are too tight?
I understand the theory of it being uneven cooling causing the warpage, but why would that occur just because the bolts are too tight? Unevenly tightened bolts could certainly have this effect, hence the need for the torque wrench. But suppose I evenly tightened all of my bolts to 120 ft.lbs instead of the specified ~85? Other than being a bitch to get them off by hand, or possibly harming the threads or seats in the alloy wheels, how would overtightening cause problems with the rotors?
I know I'm being picky here, just pointing out a possible urban brake legend that pops up all the time.
-- -Fred W
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Well...BMW recommends (I think, I would have to check) 87.5 lbs/ft of torque. I have to agree that tightening over that spec. is probably not going to do any real harm assuming they aren't too awful tight (like 120 lbs ;-) , but tightening them by hand with all five being equal is unlikely.
I agree that consistency is what you are after. To be consistent you need a torque wrench so you might as well do it to spec if you are going to go to that trouble.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.