E92 Complicated steering wheel/braking vibration/shimmy

[stevie99s]

Hi, I have a thread also in the bmw section however hope it's OK to put it in here too as it might get more footfall! Many thanks in advance. I've copied it from E90post as you helpful lot may be able to help too hopefully.


Drives: E92 325I m sport (n52k)
Join Date: Jun 2016
Location: Alnwick, Northumberland


Hi, please bare with me as this post/problem is a little complicated, many thanks in advance!

Basically a couple of months ago I bought a 325I m sport ( http://www.pistonheads.com/gassing/t...f=47&t=... As far as I can remember, infact I'm sure there was no vibration or problem.

With this being my first auto I did stamp on the brakes a few times thinking it was a clutch....dohhhh ?? so have done some fairly heavy braking at times.

Now the problem as I remember was when I had my alloys "refurbed and painted" the company borrowed me some se 17" alloys for a couple of days (100 miles) that had a horrible vibration present,especially bad under braking. Now I wasn't too worried as I'd assumed they were buckled etc. And I would have my fresh alloys back soon so fast forward when I got my refurbed alloys back there was still a vibration there although not as bad with the "loan" wheels.

Since then a few weeks back I have had the Mot done which it passed with no advisories, they also rebalanced the front 2 alloys as the painter had just painted over the wheel weights.

I also had a full alignment done which was out slightly.

This still didn't fix it however so my mechanic friend and myself have cleaned the mating surfaces from the wheel/ hub and the wheel bolt holes which were full of flaking paint etc. This I think has improved it slightly but the annoying vibration is still there. ??

It seems to be worse at 40/50 mph and light braking where it can be quite violent, although it's always there to a degree and I could be wrong.

My mechanic friend did say there was some "runout" on the brake discs, could it be this causing it even when not braking?

Could it be bushes or control arms? The cars got 93k on now.

Any help would be greatly appreciated as I want to get it sorted before a few long trips. Thanks for bearing with me!

[Garybee]

What do you feel the vibration through? Do you feel it through the steering wheel or just through the pedal?

[HustleRussell]

Since you're new to automatic you may have gotten the brakes hot with your heavy braking antics and then held the car on the brakes in traffic or at a set of lights. This can bake the brake friction material onto a patch on the disc which will then cause the brake to drag and release every rotation which will feel similar to an out of balance wheel.

Of course this problem can be exacerbated on a BMW with 90k miles by tired bushes etc.

Are your own wheels standard fit for the car?

[The Wookie]

It's entirely possible to have runout so bad that it takes up all the clearance in the caliper and cause slight judder when off-brake. It could have been the dirt/corrosion on the mounting face that originally caused it if it was excessive or it's also possible that the wheels you were lent had mating faces which weren't flat and have induced the runout for the time you had them on.

Worn bushes (particularly castor control bushes) will make a car more sensitive to brake judder too so that may not be helping

[stevie99s]

Thanks chaps for the responses, to answer a few questions. Yes it's felt through the steering wheel at all speeds above 30ish, it always seems present but perhaps slightly worse from 40-50ish. You can see the wheel shaking slightly on a straight line.

Under some braking it can be quite violent and the steering wheel shakes a lot however I think it slightly improves after a long fastish drive but is still present.

The front discs are relatively new so the mechanic has advised against replacing them but I may just bite the bullet and try it?

Cheers

[The Wookie]

stevie99s said:

Thanks chaps for the responses, to answer a few questions. Yes it's felt through the steering wheel at all speeds above 30ish, it always seems present but perhaps slightly worse from 40-50ish. You can see the wheel shaking slightly on a straight line.

Under some braking it can be quite violent and the steering wheel shakes a lot however I think it slightly improves after a long fastish drive but is still present.

The front discs are relatively new so the mechanic has advised against replacing them but I may just bite the bullet and try it?

Cheers

There's plenty of places that have on car disc skimming setups which are perfect for a lightly worn set of discs that have changed shape for whatever reason.

Worth getting the hubs and such checked for flatness if you can find a garage that knows how to use a DTI, also worth making sure that your pin sliders are working as they should with little or no lateral play and that the caliper pistons aren't sticking, as it could just be a coincidence that the judder has appeared with the wheel changes.

[Dave Brand]

[quote=stevie99s]The front discs are relatively new so the mechanic has advised against replacing them but I may just bite the bullet and try it?

[/quote

Slightly silly advice - if they are the cause of the problem, they need to be replaced irrespective of age.

A quick check for runout if you haven't got a DTI is to use feeler gauges. With the wheels off, check clearance between disc & pad every 30 degrees or so of hub rotation. As the Wookie says, you really need to check the hub faces as well.

It could, as has also been suggested, be friction material build-up on the discs, in which case giving them a really good workout will probably cure the problem . . . if it doesn't, it will still be fun!