Vibration under braking (Cross post to SE1)

Stewart · Post by **Stewart** » Sat Jul 08, 2006 7:12 pm

I have recently developed a vibration whilst braking. Not that sure I can hear anything, but can definitely feel it through the pedal. Can't really say if it is from the front or the rear or the left or the right although at a push I would say front left. The vibration isn't there at any other time.

Any thoughts on what the cause may be?

The car is a 99 S1 with 46k miles. I just recently had the 2 rear tyres replaced and have only felt the vibration since then, although this is probably just coincidence.

I think the brake pads were changed about 6k miles ago and look okay, at least on the outside. I think the brake disks may also be on their last legs as they are quite grooved and glazed.

Cheers

Stewart

MacK · Post by **MacK** » Sat Jul 08, 2006 8:46 pm

Hi Stewart,

Sounds like it could be a 'warped' or a rusty disk.

Is it there all the time?

With a bit of a run and some heavy(ish) breaking, if it's rust then that should clear it. I had similar probs on my old disks.

With warped disks, it could be a build up of brake dust etc on the disk surface giving an inbalance on the disk, some enthusiastic/heavy breaking might clear this up, or else getting the disks skimmed should do it. Though if you think the disks are past their best then just getting new ones should sort it.

2p

John

Stewart · Post by **Stewart** » Sat Jul 08, 2006 9:25 pm

MacK wrote: Sounds like it could be a 'warped' or a rusty disk.

Is it there all the time?

John

Only there while braking. It is what I would imagine a warped disk to feel like, but not sure why that would appear all of a sudden after 46k miles? I have not over heated them or the like. Only been driven on the road at moderate speeds.

MacK · Post by **MacK** » Sat Jul 08, 2006 10:10 pm

bernie_eccle wrote:Only been driven on the road at moderate speeds.

Speed up a bit and hit the brakes harder, see if that clears them.

I understand that brake dust build up on the disk can cause the symptom of 'warped' disk. i.e the disk surface is not flat, so when the pads touch it there is a pulseing sensation felt through the pedal and steering wheel. Doing a few high speed stops might help clean up the disk.

I wait to be corrected by more technically competent posters

p.s. my disks lasted 28,000 miles (from new as far as I know) so maybe yours need changed due to wear anyway.

Uldis · Post by **Uldis** » Sun Jul 09, 2006 8:03 am

Did this happen at the same time they changed pads?
Because if they removed a disk and while re-seating it there was some rust in the inner face, it could have been mounted slightly slanted, putting it out of true.
If this was the case you would feel also a longer pedal travel.as the side to side motion pushes them apart.

If not, it must be a variation in thickness, possible if you ore the mechanic left the car unused for some time outside and the disk faces got rusty.
SOmetimes aggressive use will clean them, sometimes you need skimming. Since they're on their last legs you would replace them instead.

FWIW I don't rate the original isks very high, may be the time to upgrade.
But if the managed to last you 45K, another set of originals would do fine.

Stewart · Post by **Stewart** » Sun Jul 09, 2006 9:01 am

Uldis wrote:Did this happen at the same time they changed pads?

FWIW I don't rate the original isks very high, may be the time to upgrade.
But if the managed to last you 45K, another set of originals would do fine.

Uldis

Thanks for the response. The pads have not been changed recently, but seem to still be in good order.

I think I may just bite the bullet and get new disks. Is this a DIY job? Should I do all 4 at the same time? Can I still use the existing pads or best to get new ones (greenstuffs at the moment).

Is it possible a wheel bearing could be causing the symptoms or some other steering/suspension part?

Stewart

Uldis · Post by **Uldis** » Sun Jul 09, 2006 10:39 am

A wheel bearing could have some similar effect but not exactly the same.
Yu can reuse pads provided you sand them flat, other wise you'll pass the imperfections to the new disks.
But for what the EBC greens cost, I would change them anyway. Let's say, if after sanding them flat (against a piece of glass with sandpaper you still have more than 1/2 life out of them you caould use them.

And yes, you can change all 4 and it's a DIY task, but if I was you I would change only the ones that need changing.

MacK · Post by **MacK** » Sun Jul 09, 2006 6:46 pm

I recently changed my pads and disks myself, look down a page for the thread.

Not too difficult to do, and could easliy be done at a 'spanners and sponges' session, esp if just fronts.

John

Victor Meldrew · Post by **Victor Meldrew** » Sun Jul 09, 2006 8:27 pm

I recently had a problem with mine after the car was laid up for a bit... take the pads out and clean out the groove that runs down the middle of the pad, that is where the rust and grit can build up causing a similar problem.

It may not fix it, but check this out first before forking out for pads... but as Uldis says, for the price of the green stuff, just change them out unless your on a budget.

Stewart · Post by **Stewart** » Thu Jul 13, 2006 7:41 pm

Well the vibration is almost gone now. After advice from SEr's here and on SE1 I gave brakes a fairly hard thrash last night. That was further complimented by taking the car to work today and travelling back from Perth to Fife via Creiff, Gleneagles, Glendevon and Kinross

The bite is back and the vibration is as good as gone.
Must add that the first thing I did was check the wheel nuts as advised on SE1 - they were all FT.
I still think I will have to buy disks at some point with in the next few thousand miles, but I'll see how I get on for now.

Thaks for the help.

Stewart