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-   -   Vibration under braking (http://www.maxbimmer.com/forums/showthread.php?t=158575)

sergiomordo 07-04-2013 12:43 AM

Vibration under braking
 
Hi,

2-3 months after I bought my 323ci, my steering wheel started to shake under braking at high speeds. Therefore, I got the rotors resurfaced. Problem was solved for another 2-3 months and it came back. This time, I replaced the rotors and also pads. Again, couple months later, vibration started to come back. I thought one of my calipers had a problem, which causes one pad to always touch the rotor, therefore heat only one side of rotor while other side is cool, which warps it. So I replaced both calipers and rotors, kept the same pads. Problem went away for couple of months again. I recently drove from Toronto to New York, and the problem started again. It looks like when I drive long periods of time on highway, the problem comes back. After spending so much time and effort on this, I do not know what causes the warping and how I can fix it.

Does anyone here have any idea what my problem might be? I use Zimmerman coated rotors btw.

Thanks a lot,
Sergio

jabela 07-04-2013 01:20 AM

How would you describe how you apply the brakes? Early and light, or late and hard? Ever engage ABS?

Do you get the vibration on light and very hard braking?

Are there any groves in your rotors? What pads/rotors are you using? OEM?

Have your control arm bushings been replaced recently?

Have you had a good alignment performed recently?

How violent is the shimmy? Slight vibration? Or strong oscillation in the steering wheel?

sergiomordo 07-04-2013 01:49 AM

I would describe the braking as early and light. When I apply very heavy braking, very late, the vibration effects are not too much. But when I am going 120, and I apply light braking, I get very strong oscillation in the steering wheel, which also makes noise probably from the steering system. But this vibration started as very minimal, and kept increasing as I drive more and more on highways.

There are no groves on the rotors. They are currently Zimmermann Coated rotors. When I had the problem before, I had a different brand of rotors that I do not remember, it was what my mechanic put on. And before that, it was whatever I bought the car with.

I have pads that my mechanic ordered for me. He told me that they are very good quality pads, which also have ceramic compound. But I remind you that this problem occured before I replaced the pads and rotors also, with the set up that came with the car when I bought it.

ABS does not get engaged during this vibrations. But I did have very hard braking couple times since I got the car, which engaged ABS. Maybe like 2 or 3 times.

I recently replaced my tires and one tie rod. Therefore, I had all 4 wheels balanced, and had an alignment. When I am not applying the brakes, the car just slides on the road, with absolutely no vibration, and goes straight.

No my control arm bushings were not replaced since I owned the car for the past year and a half. But I do check those things occasionally and never saw any play on them so far. Swaybar bushings were replaced long time ago.

As I said, the vibration started as a very slight vibration under braking, but now it is a very strong oscillation of the steering wheel.

I can feel the bent rotors when I am slowing down at low speeds for a red light. For example going from 20km/h to 0, I can feel the car push me forward and back, as the brakes hold more and less, more and less, kinda like what happens when you have a bent rim on a bicycle, rim touches the pads and goes away, touches the pads and goes away.

jabela 07-04-2013 03:20 AM

Pretty much all E46 should have had their fcabs replace by now, so it could be that they are failing and wobbling under light braking.

However, since it goes away when you change the brakes it's probably not the fcabs.

It most likely is uneven pad deposits in your rotors. Did too properly bed the new brakes in? Make sure you do that. You may need to do it a few times to wear off the deposits. Swapping pads out to a more aggressive pad can help clean them off too. You should also try braking harder more often, like coming to a stop or getting off the highway. Just make sure no one is behind you. Basically brake later and harder instead of early and light. it will also extend the life of your brakes.

My understanding is that warped rotors on modern vented disc brakes is a myth. It's really just uneven deposits.

sergiomordo 07-04-2013 11:53 AM

To be honest I never heard of bedding the brakes in. I think I will get some new pads, and resurface the current rotors and start fresh. After I get those installed, I will make sure I properly bed them in.

When I am driving I usually brake hard and late, only when there are people in the car I try to brake softer and earlier. I will try to change my habits based on your comments.

Thanks a lot for the help, much appreciated.

jabela 07-04-2013 12:04 PM

Seriously, just try bedding them in a few times to clean them up. Worst case scenario is that it doesn't work and you start fresh. I don't think resurfacing is worth the cost, and many places won't do it properly. May as well just get new rotors. You could even clean them up yourself with some brake cleaner and steel wool. Don't use sand paper though. The silica will ruin the rotor.

I think I have some old pads you could use if the 323 has the same pads as the 325, but I'm in etobicoke.
Would probably be a good idea to clean and lubricate your calipers too.

Here's zeckhausen's instructions.
http://zeckhausen.com/bedding_in_brakes.htm

Bforte 07-05-2013 01:07 PM

Hey man I just started experiencing the same thing a few weeks ago... mine is a seized calliper.

jabela 07-05-2013 01:25 PM

Yep... ideally should service your calipers at least once a year, cleaning everything and greasing contact points. Also cleaning the guide pins and lubricating them with silicone.
If you haven't replaced the rubber bushings for the guide pins by now, you should do that, as they are most certainly worn and gummed up.

sergiomordo 07-05-2013 03:58 PM

Thanks a lot for the help and comments, I will try to bed them in today, and will post more information later.

sergiomordo 07-05-2013 03:59 PM

Bushings should be fine because both front calipers are just 2-3 months old.

BmW1819 07-05-2013 08:00 PM

I hope u cleaned the hubs where the disc mounts too?

Trekz 07-05-2013 09:36 PM

and make sure wheels are torqued properly in a star pattern. In theory improperly torqued wheels can warp rotors.

sergiomordo 07-07-2013 09:47 PM

Yes I did clean the hubs where the discs mount.

However I do not torque my wheels. I just tighten them in a star pattern. I will keep that in mind, thanks.

jabela 07-07-2013 09:51 PM

Quote:

Originally Posted by sergiomordo (Post 1616590)
Bushings should be fine because both front calipers are just 2-3 months old.

Who replaced the calipers for you? The old ones could have been reused. Also, how sure are you that you got new calipers? There are some shady shops around.

sergiomordo 07-07-2013 09:58 PM

I buy all my parts from online suppliers, either germanparts.ca, bimmerspecialist.ca or autopartsway.ca.

Calipers were actually rebuilt ones bought from autopartsway.ca. I can not afford brand new calipers.

I get all work on my car done at a shop in Finch and Keele. It is not a BMW specialist shop but he is a good mechanic and I have been going to him for more than 2 years now. I can watch him as he works on my car to make sure everything goes well.

I also did send my old calipers to autopartsway.ca to get back the core deposit. They pay you 50 bucks for each caliper. Not bad.


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