# Brake rotor balance



## geomax (Dec 22, 2001)

Has anyone ever had to replace their brake rotors because they were "out of balance"? I did some searching in the archives over on the .org, and it seems BMW's are known for having brake rotor problems to some extent.

What are the symptoms of the rotors being out of balance?


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## JPinTO (Dec 20, 2001)

If the rotors are warped then you will get shutter in the front wheels under braking. The shutter may come and go at different speeds.


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## geomax (Dec 22, 2001)

JP - 

The jist I got from reading the archives is that warped rotors and out of balance rotors are actually seperate problems. Or are they in fact the same? It's puzzling how a brake rotor can be out of balance, but it appears a number of posts indicate that people had to change their rotors because of a shudder they experience while highway driving (ie, not during braking).

Any insights? Anyone?


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## Emission (Dec 19, 2001)

Considering they are cast iron, they could (in theory) be out of balance. I have noticed that some rotors have material cut out of them (I always assumed for balance).

It is well known in the "Honda-universe" that the best way to balance the tires is on the car. They spin the wheel, tire, and rotor to speed and balance them as a unit. Interesting, but not done much on BMW's.


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## geomax (Dec 22, 2001)

Emission said:


> *It is well known in the "Honda-universe" that the best way to balance the tires is on the car. *


Yeah, I've heard of this method, but I've never come across any mechanic or shop that does this. Do most honda dealers do this then?


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## Emission (Dec 19, 2001)

Good question.

I'd call a few dealers (Acura too) and see if they do it this way.


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## Kaz (Dec 21, 2001)

There is a chain of brake/alignment shops in SoCal called Bear Frame and Axle or something like that that does all their wheel balancing on the car.

If the car has hub/bearing/rotor balance issues, thic could help, but it may go out of balance as the tire wears, and also if the wheel is removed and put on another location on the car, or even with a different orientation back on the same axle (ie. comes off with valve stem up, goes on with valve stem down).

I think 3-way dynamic off-car balancing is better (I think most modern balancers are this way; they can check for out-of-round and sideways wobble), and treat unbalance on the car itself (bearing/hub/rotor/wheel centering, etc.) as a separate issue.


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