[deanmc]

I need some help diagnosing my brake juddering. Here what I know:

1) Steering wheel shakes only when braking from ~65 mph to 40 mph.
2) No pulsating of brake pedals, only in the steering wheel.
3) Only happens when braking at greater than 40% pedal pressure. When I step on the brakes lightly, the juddering is not as evident.
4) Front brakes are Stoptech pads and Stoptech slotted rotors, rear brakes are OEM (Textar) pads and OEM BMW rotors.
5) Front setup was installed approx. 1200 miles ago, Rear pads were installed 800 miles ago. Juddering started about 600 miles ago.
6) Last brake flush was last year, about 23K miles ago.
7) Pads were bedded in using Stoptech recommended method.
8) I tried to re-bed the pads, but it hasn't helped.
9) Car has never been tracked.
10) Wheels/tires are roadforce balanced, no vibratiionissues when accelerating or cruising.

I read that it might be blown lower control arm bushings, and I also read that it may be uneven deposits. Can someone provide some insight into this? I appreciate any help I can get, as this is pretty f'ing frustrating.

[Lagger1]

sounds like classic warped rotors dude. Did you turn them or replace them 1200 miles ago?

[The HACK]

Originally Posted by deanmc

7) Pads were bedded in using Stoptech recommended method.

Did you try to do this yourself, or did someone that actually knows how to bed in a set of pads do it for you?

I only ask, because NO ONE seems to know how to bed in pads right no matter how well the instructions are written. So typically for anyone who never tracks their cars, I just tell them not to bother bedding in their brakes, since if you don't do it right, what you described is what happens.

It's not an exact science. You have to know when the pads are hot enough to transfer, and once you do it (get one or two layers of transfer laid down) you can not use your brake again until the system completely cools off. The only place to do it properly is if you have access to a long road or a giant parking lot, or to do it at the track if you have access to a warm-up session. Otherwise, the smallest amount of imperfection on the bed-in process will leave enough deposit that results in a high spot.

And no, modern rotors don't warp. Unless they come from the factory unbalanced and out of round, if they didn't exhibit this "judder" when new, they're not warped.

[deanmc]

Originally Posted by Lagger1

sounds like classic warped rotors dude. Did you turn them or replace them 1200 miles ago?

Both pads and rotors were replaced 1200 miles ago. And my understanding is that modern rotors don't "warp," or at least it takes an immense amount of heat followed by a quick cooling period to do so. So I'm pretty sure they're not warped.

Originally Posted by The HACK

Did you try to do this yourself, or did someone that actually knows how to bed in a set of pads do it for you?

I only ask, because NO ONE seems to know how to bed in pads right no matter how well the instructions are written. So typically for anyone who never tracks their cars, I just tell them not to bother bedding in their brakes, since if you don't do it right, what you described is what happens.

It's not an exact science. You have to know when the pads are hot enough to transfer, and once you do it (get one or two layers of transfer laid down) you can not use your brake again until the system completely cools off. The only place to do it properly is if you have access to a long road or a giant parking lot, or to do it at the track if you have access to a warm-up session. Otherwise, the smallest amount of imperfection on the bed-in process will leave enough deposit that results in a high spot.

And no, modern rotors don't warp. Unless they come from the factory unbalanced and out of round, if they didn't exhibit this "judder" when new, they're not warped.

I bedded them in myself following instructions on Stoptech's website. Went down a nice long stretch of road with no lights at 2am in the morning. Followed that by driving on the highway with no braking to letthem cool. I thought that high spots would eventually get scrubbed off with normal driving and braking, but the juddering has gotten worse. Do you know if I can re-bed them?

[The HACK]

Originally Posted by deanmc

I bedded them in myself following instructions on Stoptech's website. Went down a nice long stretch of road with no lights at 2am in the morning. Followed that by driving on the highway with no braking to letthem cool. I thought that high spots would eventually get scrubbed off with normal driving and braking, but the juddering has gotten worse. Do you know if I can re-bed them?

If at any time you activated the ABS system, or come to a complete stop during the process, the it's possible that there's a slight high-spot on the rotor due to deposit that will eventually get larger as more pad material gets deposited unevenly in that same spot.

If after the bed-in process, you washed your car and allow rust to build up for an extended period of time without burning them off, same deal can happen, high spot on deposit except it'll be rust deposit.

Yes high spots can potentially be scrubbed off, but it can also lead to further deposit being left behind on one side of the high spot and therefore lead to more judder as well. There are a couple of ways to "cure" this problem.

1) Hose down your rotors. Wait for about 30 minutes, there should be a nice layer of rust developing on it. Go find a big empty lot and do a couple of hard stops, but not so much that the rotor gets glowing hot like in a bed-in process. While "cold" the pads should scrape away the rust and take that layer of uneven deposit with it.

2) If the above method does not work, get a set of REALLY aggressive pads, like Hawk HT-10 or DTC-60 or better, put them on the rotors, and go for a couple of really hard "stops" while the rotors are cold. The high metallic content of these pads should literally remove a very thin layer of rotor material and take all the excess deposit with it.

After that, if you're not taking the car to the track, do not bed-in. If you ARE taking the car to the track, then follow StopTECH's bed-in process to a tee, do NOT activate ABS and do NOT come to a complete stop.

[deanmc]

Thanks Hack, #1 is exactly what I'm looking for, a way to to scrub off deposits without buying another set of pads. But do you know why I'm only experiencing juddering while braking at certain speeds or pedal pressure?

[Atomicteal_M3]

Suscribed! I'm kinda in the same boat!

[fdriller9]

Did you installed the anti-rattle clip correctly?

What about your guide pins? How did they look when you replaced your brakes? Did you clean and lube them?

[deanmc]

Originally Posted by *********

Did you installed the anti-rattle clip correctly?

What about your guide pins? How did they look when you replaced your brakes? Did you clean and lube them?

A local shop did the install, but I've since taken the pads off to put anti-squeal on the back.

I made sure the clips were installed back correctly. And I took off the pads by removing the guide pins and sliding out the caliper housing. Pins looked good, but could they be the source if I didn't torque to spec? I did notice that the lube was pretty sticky.

[Babydragon]

Originally Posted by deanmc

A local shop did the install, but I've since taken the pads off to put anti-squeal on the back.

I made sure the clips were installed back correctly. And I took off the pads by removing the guide pins and sliding out the caliper housing. Pins looked good, but could they be the source if I didn't torque to spec? I did notice that the lube was pretty sticky.

More than likely it's not a warped rotor because the brake pedal would pulsate.

[qtrlifecrisis]

Originally Posted by hajduk

More than likely it's not a warped rotor because the brake pedal would pulsate.

correction, warped rotors do not make the pedal pulsate. you're thinking about warped drum brakes.

guys, brake calipers are floating on rotors, that means if the rotor moves side to side, the caliper does also. but that wont make the pedal pulsate in most cases. because it's not actually forcing any brake fluid back up the line.

you'd probably heard that before from a mechanic or "through the grape vine" after a mechanic said that it will happen with warped drum brakes. think about it, a drum brake is a cylinder wraped around brake shoes that press outwardly against the drum. if that drum is warped it will force brake fluid back to the reservoir, and all the way back to the pedal.

with that said, i'm not claiming i know what the problem is, as i haven't seen/driven the car. could be LCA bushings, it could be a non-wearing part in the steering that has become worn out.

and another recommendation, don't put cold water on hot brakes. and avoid large puddles. thats an easy way to get warped rotors.

you should be able to take the rotors off, take them to a shop and ask them to put them on the lathe WITHOUT cutting them, just to check if they are true. if you need a shop to do it at, i know some guys here in burbank that will take care of you.

cheers.

[TurboBimmer]

Sounds like uneven brake pad deposit on the rotors. I have the same problem after trying to bed-in Cool Carbon pads on used OEM rotors.

"Luckily" the rotors on my car need to get replaced soon anyway, so I'll switch to EBC slotted rotors while keeping the pads.

So +1 on what the The Hack wrote.

[raceyBMW]

I know on my E34 that a 65mph shimmy was most of the time a result of worn thrust arm bushings, but probably not the case here since its still a pretty new car.

[deanmc]

Turns out it was uneven deposits from improper bed-in the first time around. I re-bedded the pads by doing 3 sets of 10 stops from 60-10mph, then drove around for 10 minutes to let the brakes cool down. No more vibrations when braking, and my rotors have a nice blue-gray sheen now!

[Anthony@BimmerBrakes]

Originally Posted by deanmc

Turns out it was uneven deposits from improper bed-in the first time around. I re-bedded the pads by doing 3 sets of 10 stops from 60-10mph, then drove around for 10 minutes to let the brakes cool down. No more vibrations when braking, and my rotors have a nice blue-gray sheen now!

Glad you go this all figured out. I was about to say warped rotor due to improper bedding.

-Anthony@BimmerBrakes