Replacing brake rotors: Fact or Fiction?

[Montreal525]

the proper way to do it is replace all 4 pads as sets and either replace the rotors if they are below spec thickness or have them turned at a machine shop but never install new pads without new rotors or at least turning you old ones

Ha... Done it couple time, on almost all my cars, with no problems... I have Brembo x-drilled rotors in front and just changed the front pads this summer. The rotors were well within specs and looked good. I didn't even take them off....

I believe it's all in the breaking period...

Jeff

[MTV]

Thrust arm shimmy is usually felt between 45-55 mph, or thereabouts, and is usually worse under braking.

Thanks for the info. I will keep an eye on it on my way home from work tonight.

[tdgard]

I change the rotors as a matter of course every time I do the brakes. When I bought my first BMW, I had the "well I've never done this on any other car" mentality. First time I took the rotors to a machine shop, they told me they could not turn them (which I DID do with every other car). This is because if you measure the new rotors with a caliper, they are built to spec. No extra metal to take off. Being stingy, I tested it. I found that I could never make it to the next brake change without developing a shimmy of some sort while stopping.

So based on lazyness, I now change the rotors every time on the front so I do not have to take the wheels off a third of the way through the second set of pads. It's amazing what spending a nominal amount of money will do to keep this from happening.

That being said, I let my rears go twice since I can not feel the effect.

[boardburton]

Where can I purchase these $20 BMA rotors?

[Blitzkrieg Bob]

http://www.bmaparts.com/

[rob101]

From looking at my rotors after nearly one set of pads and 40,000kms I'd say that they are already undersize. At least a 2mm lip each side... so machining is out.

2 mm?
thats HUGE!

[bmwalfa]

im looking at doing this to my car also, im thinking of putting drilled and slotted brembos on the front, and drilled in the rear, ive helped with a few brakejobs, and trust me, if your budget can allow, and you like to get into that gas, do at least drilled, also i believe a cooler pad lasts longer.
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also check your rear rotors, it could be those that are warped, ive seen this happen on some larger trucks and suv's but i wouldnt rule it out for a bmw.

[632 Regal]

from what I understand which isnt much is the surface it heat treated and once cut the treating is gone. thats all I understand and dont know if its fiction or truth, the rotors are thin and excessive wear in a cut rotor makes sense, the hardness is gone.

[bsell]

My brakes are getting low, I have been told that if I replace my pads and sensors that I should replace my rotors. I have never had to do this on any other car I have owned, but is this something particular to BMW's?

Do they just want more money out of me or is it a good idea.

The money is somewhat of an issue but long-term customer satisfaction and ease of repair play a role also. Using brand new rotors removes any hidden issues with the old rotors popping up later plus the mechanic doesn't have to wait for the machine shop to finish turning your old rotors. I've had machine shops rush the turn job and leave grooves like an old LP record. Ever heard brake pads go 'clack, clack, clack' down the street? The grooves grab the pads and slap them around in their mounts, not good!

Change out your brake fluid while you are at it. You will be amazed at how much more abuse the brakes will take before they start fading. Remember, brake fluid absorbs water and water boils at 212 degrees which is way short of DOT 3 and 4 brake fluid. Plus the fresh fluid can help keep the rubber parts protected longer.

Brian

[Airborne001]

Thrust arm shimmy is usually felt between 45-55 mph, or thereabouts, and is usually worse under braking.

Sounds like my car, can the thrust arms be replaced without rebuilding the whole front suspension? Do you need any special tools (presses/pullers) to do the job?