brake disc skimming

brake disc skimming

Author
Discussion

jdearden

Original Poster:

1,746 posts

177 months

Wednesday 28th October 2015
quotequote all
hi guys want to get my discs skimmed on the r8 to remove the lip. got new pads that i want to fit so thought id get them skimmed at same time.

any recomendations in the hampshire area

ecain63

10,588 posts

175 months

Wednesday 28th October 2015
quotequote all
You are aware of the limited tolerance on the discs on the R8? If you skim them you're only going to reduce the life further, no matter how little they take off. If the lip is that bad i'd suggest new discs.

barryrs

4,389 posts

223 months

Wednesday 28th October 2015
quotequote all
As above if they are still within tolerance once skimmed I would recommend using www.skimmydiscs.co.uk

You will need a premier garage though as IIRC the standard equipment only goes to circa 340mm discs.

jdearden

Original Poster:

1,746 posts

177 months

Thursday 29th October 2015
quotequote all
What do you mean regards the tolerances.

barryrs

4,389 posts

223 months

Thursday 29th October 2015
quotequote all
If you look up the manufacturers specifications the disc will have a minimum thickness and if you are close to this limit the process of skimming may create a safety issue.

ecain63

10,588 posts

175 months

Thursday 29th October 2015
quotequote all
The minimum thickness is normally stamped on the bell of the disc for easy reference.

Steve_D

13,746 posts

258 months

Monday 2nd November 2015
quotequote all
A quick google found thickness new 34mm. Minimum thickness 32mm.

So not much to play with.

Steve

jdearden

Original Poster:

1,746 posts

177 months

Tuesday 3rd November 2015
quotequote all
It just seems like such a small tolerance considering how big and thick the discs are. Makes me think they are just getting people to change disks more often.
The dealers seem to suggest replacing the disks with the pads each time.

ecain63

10,588 posts

175 months

Tuesday 3rd November 2015
quotequote all
It's no scam, the tolerance is just very fine. As soon as my M5 discs went beyond minimum thickness they began to distort with heat as they expanded unevenly. You've bought a junior supercar at a % of its original cost. The maintenance costs have not depreciated in the same way unfortunately. Just replace the discs and enjoy.

Lofty999

288 posts

127 months

Wednesday 4th November 2015
quotequote all
Had the same issue on a previous 350z,once skimmed the discs only lasted another1000 miles before I had to replace them!Dont think I will bother to skim again.

julian64

14,317 posts

254 months

Wednesday 4th November 2015
quotequote all
Handwringing much?

I have done this to my own discs many times. It isn't a given that you have you make the disc thinner to skim them.

If the disc is flat but has a lip then you can simply remove the lip either on a lathe or a mill, and to be honest its quite a sensible thing to do on a lipped disc if you are putting in new pads.

If the disc is uneven then the idea that leaving it uneven is somehow safer than removing the uneveness is daft.

If someone suggests they have to remove a big chunk to get a flat disc then I would simply go elsewhere.

I suspect its simply a case of having a close look at your discs, if they don't run true, or the undulations break the minimum level then you're better off replacing.

One last point, 2mm is not any sort of fine tolerance. 2mm is a very very large distance for a lathe or mill. If you had any marks on the disc which were 2mm or even close to that you have far bigger problems than a skim.

Jon_Bmw

619 posts

202 months

Wednesday 4th November 2015
quotequote all
How do you think the lip got there then?

If it is that noticeable that the OP thought about removing it, then safe to say it is probably close to 1mm each side....

To normal people this would give the indication the discs are at their wear limit?

Why doesn't the OP mic up the disc and check its width?

ecain63

10,588 posts

175 months

Wednesday 4th November 2015
quotequote all
It's 2mm over 2 sides, not just one. And a lip on the edge of the disc will be way into that 1mm tolerance. As suggested above, get the micrometer out and tell us the current state of play!

jdearden

Original Poster:

1,746 posts

177 months

Thursday 5th November 2015
quotequote all
Well it looks like I've gotta stop being tight and replace my disks.
Winter jobs are now clutch and disks and pads.
Only issue is I wrote off my other car on Friday so only have the r8 until end of Jan when new car will be delivered.

alyR32

764 posts

177 months

Thursday 5th November 2015
quotequote all
I was in the same position with the front discs on the RS4, considered getting them skimmed, but after advise from on here decided to bite the bullet and fit new discs, in the end glad it was the route I took.

julian64

14,317 posts

254 months

Friday 6th November 2015
quotequote all
Jon_Bmw said:
How do you think the lip got there then?

If it is that noticeable that the OP thought about removing it, then safe to say it is probably close to 1mm each side....

To normal people this would give the indication the discs are at their wear limit?

Why doesn't the OP mic up the disc and check its width?

The lip obviously gets there because its an area of the disc the pad isn't pressing on either evenly, or at all. Not sure what other answer you were expecting there?

Not sure where the op mentions the thickness of the disc or how close it was to tolerance. You seem to be saying if a lip can be felt at all then you have lost 2mm of thickness. If thats the case then your argument is somewhat bizzare and I would have to disagree.

Perhaps if the op were to measure the disc we could all have a better opinion. However if the op wants to leave it at asking the question as is, and the general advice from here is that if any lip is palpable then the discs should be replaced. Then I'm not sure why you are even suggesting he 'mic it up'.

IMHO changing the disc with every set of pads because you can palpate a lip is nonsense IMHO.

Jon_Bmw

619 posts

202 months

Friday 6th November 2015
quotequote all
The lip got there because the pads have worn the disc! Whether the wear is beyond the manufacturer tolerances it can only accurately be measured with a micrometer.

Now most people don't have a micrometer in their back pocket, so we have to go with a bit of common sense and logic. If you are concerned enough to want to remove a lip because you think it will negatively affect the new pads (like the OP), then safe to say that lip is probably quite deep. This disc can only have 1mm wear on each side before it is out of spec, hence all the normal people suggesting to replace the disc...


Alucidnation

16,810 posts

170 months

Friday 6th November 2015
quotequote all
Skimming brake discs?

Do people still do that???


Anyway, as pointed out already, even a cheap supercar still has supercar expenses.

Just get the new discs and pads fitted and enjoy it.

It's stil a great car, regardless.

jdearden

Original Poster:

1,746 posts

177 months

Saturday 7th November 2015
quotequote all
Well that little innocent question exculated quickly. Lol
The lip is behond the tolerances so will replace. I was just trying not to spend money that wasn't needed. Turns out it is needed.
I skimmed discs on noble when I had it and worked a treat. Place I had it done at has gone out biz, hence original question.

Thanks for all advice. And help guys.

Anyone know a good place to buy discs from.

Bart 124

527 posts

189 months

Saturday 7th November 2015
quotequote all
jdearden said:
Anyone know a good place to buy discs from.
eBay matey - some gems on there, full discs & pad set for £69.95 delivered.

Can also get a Dog guard, wheel trims, LED washer jets and a Plug & play chip for 20+bhp for like £17.

I jest. I'm sure Eddie on here will have some good suggestions for sourcing discs and pads, or a few other locals