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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > Rotor temps?



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      01-07-2013, 02:02 PM   #1
asus389
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Rotor temps?

In trying to figure out why I have developed brake judder 3 times in one year over two sets of different pads/rotors I got an infrared thermometer gun. I drive around for a bit and then I point it at my rotors in attempt to see if any of them are overheated. But it occurred to me, I don't know what the temps are supposed to be to begin with. Does anyone know? Thanks.
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      01-07-2013, 02:11 PM   #2
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i dont think that's going to tell you anything.
Are you breaking hard?
Try not to hold the brakes immedietely after hard braking
Check your rotors for brake pad material deposits
Don't spray your wheels at the car wash if your brakes are hot.

You said 3 times with 2 sets of brakes. Did the judder go away once? What did you do to solve the problem then ?
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      01-07-2013, 02:20 PM   #3
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I don't really brake hard or drive on the track. Its a manual car so I'm not riding the brakes. I got the car as a CPO car in 2009 and for 2 years I didn't have any problems like this. Then about 1 year ago the factory brakes developed judder when lightly braking above 60mph with about 4mm left on the pads. I also get a vibration when driving between about 65-80. The brakes were replaced and the judder when braking went away, but came back on the new brakes in a few months. The rotors were then resurfaced, but the same thing happened again within a couple months.

The vibration when driving never really went away when changing the brakes or resurfacing the rotors and has been there over more than one set of tires and multiple balancing attempts.

So I'm trying to decide what to do. I suspect there is something underlying this problem, but am unsure how to figure it out. I guess I was trying to see if maybe a caliper was sticking by using the temp gun.

Last edited by asus389; 01-07-2013 at 02:25 PM.
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      01-07-2013, 02:29 PM   #4
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Quote:
Originally Posted by asus389 View Post
The vibration when driving never really went away when changing the brakes or resurfacing the rotors and has been there over more than one set of tires and multiple balancing attempts.
In that case its most likely NOT the brakes but something else loose in the suspension. My 2 e39s suffered from this when the front control arm bushings started to fail. If you can get the car on a hoist, pull hard on the wheel left and right and look for movement in the bushings. If the wheel shakes like crazy while braking its in the front. Otherwise its the back
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      01-07-2013, 02:37 PM   #5
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Yeah thanks good point about the bushings.

There seems to be two things going on here, both vibration in the steering/pulsation in the pedal when lightly braking above 60 mph and also vibration when not braking in the 70-80 mph range.

I guess the thrust arms could be bad but if that was the problem then why would the vibration when braking go away temporarily for a few months when I replaced the brakes and/or resurfaced the rotors? Do bad control arms cause rotors to wear unevenly?

The front thrust arm bushings were already replaced once around the same time I replaced the brakes the first time, but I suppose they could be bad again.
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      01-07-2013, 02:45 PM   #6
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Getting vibration NOT braking is a sure sign its suspension. You did not say if the steering wheel shakes or not.

I don't know why the vibration would go away if it were the thrust arm. If asked to imagine some scenario where this would happen i would say maybe if it was winter, the bushings could be stiffer and cause less play but i'm grasping at straws there.
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      01-07-2013, 03:24 PM   #7
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Beside suspension bushings, or other suspension alignment problem, it could aslo be an out-of-round wheel, or even simply a missing balance weight.

Bad suspension geometry (or unbalanced wheel) can cause pad material to depose unevenly on the rotor, and does cause brake shudder eventually.
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      02-13-2013, 10:19 PM   #8
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Just to close the loop on this thread, I broke down and bought a dial gauge, pulled the front wheels and measured the front rotors. Both front rotors had runout, the left worse than the right. (LF 0.005", RF 0.003") I got 2 new BMW OE rotors and pads/sensors installed and the shimmy is gone. I guess I'll have to wait to see if it comes back, but at least I now I guess I have a 2 year warranty on my new brake parts. I forgot how good the initial bite on OE BMW brakes are, its kind of nice.

Last edited by asus389; 02-15-2013 at 01:53 AM.
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      02-14-2013, 06:52 AM   #9
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Do this too: pull off your rotors and get a wire brush and some brake cleaner and scrub as much dirt and rust off your hub, back and front mating rotor faces, and wheel mounting face as possible. Once you've done this, put a very thin layer of antiseize on those same surfaces.

Rust chunks can cause precisely what you are describing by forcing the rotor out of parallel with respect to the calipers, which would be felt as vibration even with brand new rotors and pads.

I have a feeling based on the symptoms you described that this is what happened to you. I always clean the mounting surfaces when I do my brakes for this very reason, even if they don't look bad.
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      02-15-2013, 12:16 AM   #10
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I would be concerned with brake temps over 600F with stock parts.

You dont have aftermarket wheels that require hubcentric rings do you?
I believe the polymer ECS rings were the cause of my premature stock rotor failure (6 months of highway driving)
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      02-15-2013, 02:06 AM   #11
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Nope no hub rings. Current wheels are rial salerno's which I'm told don't need them. Summer wheels are OE BMW wheels. New rotors were installed by BMW and I'm told they cleaned the hubs as part of their install. Given how many problems I had with my last set of brakes, when I get a chance I might break out my dial gauge again and check them for my own sanity. At least then I can see with my own eyes that I'm starting out with rotors running true.
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