Turning Brake Rotors

[Bazza79]

I'm getting brake judder on my e39 M5. I know there can be many potential causes of this and it is common on the e39 M5. I'm fairly convinced that it is uneven brake pad deposits on the surface of the brake rotor.

I've done a bit of research and I have found a few articles mentioning getting the surfcae of the brake rotor turned to remove any hi spots. The rotors were new only a few thousand miles ago and I'd like to try and save them if possible. Does anybody know if this is a common or safe practice? If so, any ideas where I can get this done? Somewhere in West London would be ideal!

Alternatively, somebody mentioned a while back that you could get a super abrasive brake pad that would clean the surface of the rotor, but they were not sure if they were still available, anybody know anything about these?

Thanks!

[The Black Flash]

It'd certainly be safe, as long as you don't take them below the minimum thickness. Can't help for places who do it though.

[thinfourth2]

Any decent machine shop should be able to do it with the discs off the car

You can even get a machine that does it with the discs on the car

[jagnet]

Brake disc skimming workshop map. One or two to choose from

[Bazza79]

Guys, thanks for your replies.

Jagnet, think you just beat me to it, found the same website..........http://www.skimmydiscs.co.uk/

Have been in contact with a couple of places got a quote of £120 from one place and waiting for a call back from AFN Porsche........sure they will probably be rediculously expensive but didn't recognise any of the other workshops listed, so though I'd ask.

They can leave the rotors on the car and just remove the caliper.

Going to book it in for next week, hopefully this will be an easy (cheapish) fix to a long standing issue.............however, I'm not sure I'm that lucky!

[E30M3SE]

Bazza79 said:

The rotors were new only a few thousand miles ago and I'd like to try and save them if possible.

Bazza79 said:

Going to book it in for next week, hopefully this will be an easy (cheapish) fix to a long standing issue.............however, I'm not sure I'm that lucky!

Reading into the above did you have the judder on the previous rotors? If so then I would be getting control arms and thrust arms checked over before any outlay on skimmimg 'new' rotors.

[Bazza79]

I didn't have the car for the previous set of rotors, so hopefully it wasn't an issue before.

I recently had new Meyle HD thurst arms fitted, complete with HD bushings. It made a small difference.

[thinfourth2]

Bazza79 said:

Have been in contact with a couple of places got a quote of £120 from one place

Bugger

I skimmed a set discs off a landcruiser for a bottle of red wine for the neighbour

[Bazza79]

ThinFourth..........really???? Where are you located?? I have a bottle going spare

[The Moose]

Serious question - obviously the American term is 'rotor' and here in the uk we have 'discs'.

Is there actually any technical difference, or just two words for the same thing?

[Bazza79]

Apologies - ahem 'discs'

Not too fond of 'american' english!

[zcacogp]

Beg/buy/borrow/steal a Dial Test Indicator (DTI) before getting the disks skimmed; that will tell you whether you will need them skimming or not.

If you are anywhere near me I'll lend you mine - or test the disks for you. For a couple of bottles of decent red, natch!


Oli.

ETA: Just looked at your profile and realised you are in London! I'm in E3 - Mile End. You anywhere near by? The offer stands.

[Bazza79]

Oli,

I'm in W4, couldn't get more opposite side of London if I tried. Had a look at those gauges on the internet and they are not cheap, plus I'm not usre how you would use it. May take you up on your offer at some point.

[zcacogp]

Bazza,

I bought one of these:

http://www.ebay.co.uk/itm/MAGNETIC-BASE-METRIC-DTI...

... when I was having similar problems with the brakes on my 944. £25 isn't that bad, and it's a useful tool (if you are into practical stuff.)

W4. Hmm. That's Kew isn't it? Very nice ... drop me a line if you are ever over this side of town - I'm happy to help.


Oli.

[thinfourth2]

zcacogp said:

Beg/buy/borrow/steal a Dial Test Indicator (DTI) before getting the disks skimmed.

A disc can run with zero runout and still suffer from brake judder as what is happening is the disc has different mu values due to pad material being picked up on the disc

[Bazza79]

Oli,

Not quite, but close, Chiswick. Thanks again for the offer. Frustratingly, I work on the Olympic Park at Stratford but I train to work. At work so can't check ebay links so will look later.

[Bazza79]

Thinfourth,

What's an MU value????

[J4CKO]

Bazza79 said:

Thinfourth,

What's an MU value????

Friction level.

[Bazza79]

Thanks Jacko, that makes sense now.

[zcacogp]

thinfourth2 said:

zcacogp said:

Beg/buy/borrow/steal a Dial Test Indicator (DTI) before getting the disks skimmed.

A disc can run with zero runout and still suffer from brake judder as what is happening is the disc has different mu values due to pad material being picked up on the disc

It can, but such high-friction patches can usually be seen pretty easily. And sometimes cleaned up with some careful use of wet-and-dry (I am told, although have never used it.)

Bazza - I presume that the disks are (visually) the same all over their surface; there aren't any darker bits any of the way 'round?


Oli.