steering wheel shakes when braking after NEW OEM rotors are installed

[SEGUA I SOGNI]

Hi there,
I have an '05 ZHP coupe (6spd) with about 86,000 miles on it. In early Jan 2014, I went to a independent mechanic, that I trust, to replace the front pads and rotors on my ZHP.

For several months before bringing it to the shop, the steering wheel would shake pretty hard during braking from pretty much any speed. So I went to the BMW dealer and bought OEM front pads and rotors and took them to the shop of the independent mechanic to have the parts installed.

Once I arrived at my mechanic's shop, they took my front wheels off. The mechanic looked at the existing pads and told me both sides on the front had at least 60-70% percent of pad left and recommended to NOT replace the pads, since the ones that were on the car were still good. So I said, okay I will return the pads to the Dealer and for him to just replace the rotors. He did so and after he finished I left and the car felt fine. I made sure to be gentle on the brake for about 200 miles and didn't notice any vibration.

Over the last month the vibration has come back and gotten a little worse every day. Now, every time I brake at any speed the steering wheel shakes unless I press on the brake pedal hard. At first it was barely noticeable, but now its really bad.

Can anybody please tell me what is going on? I doubt the rotors I bought from BMW were warped when I bought them and my independent mechanic is saying he wont warranty any work when a customer brings in their own parts. Anybody with knowledge, please chime in.

Thank you.

[KevinC]

This one's easy - you need new FCABs.

[Lanister]

From that sounds of it, you did everything right. The fact that everything was fine initially shows that the rotors were not originally warped. It does seem as though they are both (or one of them) warped again. What could cause this is a mildly seized caliper(s), whereby it doesn't disengage the pads fully from the rotor(s). This causes constant friction and thus heat build-up in the rotor when brakes are not in use. Over time, the excessive sustained heat will cause warping.

About a year ago, I bought a Honda Element with this problem. While brakes worked fine, the driver-side caliper was seized up and it quite literally cooked the rotor. The cause was corrosion from salty roads found on the east coast, where this car lived for a while.

It's easy to check if this is the cause. Jack up the front and spin the wheel by hand. It should rotate freely and spin on its own for at least a few seconds. If it doesn't spin freely, that might be the issue.

To deal with it, you'll have to rebuild the calipers (cheaper route) or buy new ones. The rotors may be salvageable if you get them machined.

[KevinC]

It's FCABs, I'd bet on it. Had exact same symptoms when I bought my car, brakes were fine. New FCABs cured it completely.

[Hornung418]

You can see the FCAB failure physically if you have someone drive the car slowly and you watch the wheels as they apply the brake slowly. The wheel will change castor visibly. Easy fix. Good luck!

[BCS_ZHP]

Jack up either front side, grab your wheel at the 3 & 9 o'clock positions and shake it. If it's bad FCABs, there will be looseness when you shake the wheel, if they're totally spent you'll even hear metal to metal clunking. But if the FCABs are tight, then it's what Giya said, you've got a stuck caliper that heated up and warped a rotor already. Since you'll have the front end in the air, spin the tire as recommended earlier.

[SEGUA I SOGNI]

I appreciate the input guys. I did some google searching and found a video of an e46 parked, and then someone using a wheel lugnut wrench to test for any play in the wheel while its parked. Movement in the wheel was a symptom of a bad FCAB. Is there an easy way to tell if one caliper is not activating at the same time as the other side? Perhaps one caliper doesnt retract all the way? The dealer said on the phone (they havent seen the car) that it could be one caliper is partially seizing and thus not hitting at the same time as the other side and creating a shaking. At all cruising speeds including highway speeds there isnt any shaking unless I need to brake. If I apply the brake softly, I get a lot of steering wheel shake until I either press the brake harder or come to a stop or let off the brake pedal.

[danewilson77]

Jack up either front side, grab your wheel at the 3 & 9 o'clock positions and shake it. If it's bad FCABs, there will be looseness when you shake the wheel, if they're totally spent you'll even hear metal to metal clunking. But if the FCABs are tight, then it's what Giya said, you've got a stuck caliper that heated up and warped a rotor already. Since you'll have the front end in the air, spin the tire as recommended earlier.

Pure, unselfish, wisdom.

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[JupiterBMW]

I would just like to add one thing... Personally, I would stop using any mechanic that tells you to reuse old brake pads on new rotors. If you're trying to save some nickels, then sure, I get it, but seriously... That's kind of like reusing an oil filter... Ok, maybe not THAT bad, but still...

Wear parts should always be replaced as a set...

But, get on those FCABs and you should be good!

[KevinC]

If those FCABs have never been replaced at your mileage, they're definitely going to be shot, even if a caliper is munged up too. Curious to see what the magic bullet turns out to be here. Good luck!

[billyjack]

I would just like to add one thing... Personally, I would stop using any mechanic that tells you to reuse old brake pads on new rotors. If you're trying to save some nickels, then sure, I get it, but seriously... That's kind of like reusing an oil filter... Ok, maybe not THAT bad, but still...

Wear parts should always be replaced as a set...

But, get on those FCABs and you should be good!

I was thinking the same thing. I guess it saves money but I'd rather save more money and not replace the rotors either until the pads are ready. Which could have been viable if the diagnosis is worn FCAB's. Either way I'd take the above advice to jack the wheel up.

[tkundhi]

Was mentioned by others, start by checking the FCAB. If they are fine, you might have one other possibility other than worn rotors. Pad deposit on the rotors. Do you know what kind of pads are on the car? If the PO put an aggressive pad that requires a high operating temp and the brakes don;t get up to that temp, it could result in to much pad compound building up on the rotors.

The fact the vibration is going away when you are braking really hard leads me to think its your pads. I don't recall FCAB vibrations stopping with increased pedal pressure.

t.

[danewilson77]

I know Bruce is in the area. He could easily diagnose and repair in about an hour.

Kids play for him.

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[jakksfor20]

One thing that you mentioned is you took it easy on the pads for 200 miles. That's a good recommendation for ceramic pads........My guess is deposits on the rotors. Do a bed-in procedure on them and see if it goes away. Get up to 45-50 mph, brake quickly down to 5mph not locking them up then accelerate back to 45-50 mph at a decent acceleration. Do that 6-8 times.

Pads and rotors, pads and rotors, pads and rotors........ say it with me.

[Lanister]

I appreciate the input guys. I did some google searching and found a video of an e46 parked, and then someone using a wheel lugnut wrench to test for any play in the wheel while its parked. Movement in the wheel was a symptom of a bad FCAB. Is there an easy way to tell if one caliper is not activating at the same time as the other side? Perhaps one caliper doesnt retract all the way? The dealer said on the phone (they havent seen the car) that it could be one caliper is partially seizing and thus not hitting at the same time as the other side and creating a shaking. At all cruising speeds including highway speeds there isnt any shaking unless I need to brake. If I apply the brake softly, I get a lot of steering wheel shake until I either press the brake harder or come to a stop or let off the brake pedal.

Usually, the issue with a seized calipers is that it doesn't let go of the rotor completely so the pads are constantly rubbing, which causes for the rotor to be constantly very hot and eventually warp. It's a common problem in parts of the country where they used salt on roads.

[3ZHP]

If you had a bad caliper, you would see uneven pad/rotor wear. Also the car would pull to the good side when braking. You haven't mentioned any of that and it's most likely the FCAB.

I have experienced that same vibration and replacing my FCAB and front control arms took care of the issue.


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[94jedi]

Glad I looked at this thread. I was going to replace my front rotors due to vibration when braking but considering that my FCAB's have never been replaced and my front rotors are less than 1 year old (and I drive it pretty easy), I'll replace my FCABs first.