Hi,

 

I've just had a service done (90k miles) and had reported a very slight shudder from the brakes above 60mph. The front discs and pads were replaced at the last service (80k miles) and as I new the rear brakes were getting low I figured that was the reason.

 

My wife picked the car up yesterday and was told the issue was the front brakes, which needed to be skimmed.

 

How could this happen? Given the original front brakes lasted the first 80k miles without issue. Note it was the same mechanic who replaced the brakes last time.

 

thanks

Matt

Did they check that the calipers weren't sticking? A sticking caliper could certainly cause warping but it'd be bad luck for both sides to show a problem like that.

Did they check that the calipers weren't sticking? A sticking caliper could certainly cause warping but it'd be bad luck for both sides to show a problem like that.

Thanks, good question. They note they "inspected brakes (pads, rotors, hoses and hydraulics). I will ask them if they checked the calipers!

Edited 13 December, 20169 yr by williamshatnerspants

how much to skim? new Mintex discs would be cheaper

 

or has the garage just bought a machine to skim with?

how much to skim? new Mintex discs would be cheaper

 

or has the garage just bought a machine to skim with?

 

37 GBP to skim. I'm waiting to hear back from them on what discs they put on at the last service..... but I'm guessing they are cheap and nasty. 

Is this from a Skoda main dealer?

 

10,000 miles on a set of discs would suggest that either the discs or pads are faulty (and therefore need to be replaced free of charge under warranty) or that there is an underlying issue causing their premature failure (given that the garage hasn't offered a diagnosis it is fair to assume there isn't one).

 

So either way there should be no cost to you. Return the car and ask that they either replace the faulty components or quote for the work needed to fix the issue that has caused their premature failure.

 

No one skims discs these days.

Is this from a Skoda main dealer?

 

10,000 miles on a set of discs would suggest that either the discs or pads are faulty (and therefore need to be replaced free of charge under warranty) or that there is an underlying issue causing their premature failure (given that the garage hasn't offered a diagnosis it is fair to assume there isn't one).

 

So either way there should be no cost to you. Return the car and ask that they either replace the faulty components or quote for the work needed to fix the issue that has caused their premature failure.

 

No one skims discs these days.

Thanks for that, its really appreciated.

 

No not a main dealer, just a local mechanic who 'specialises' in European cars. They have been pretty good up until now.

 

I will chase them up today, as they have yet to reply.

 

Cheers

Matt

Over tightening of road wheel bolts can also cause brake disc warp :nerd:

People do actually still skim discs these days, even just to clean off 'cosmetic corrosion or light scoring'. 

 

http://skimmydiscs.co.uk

A Used Car or even an Approved Used car from Skoda , VW, Audi or Seat near you might have had the discs skimmed.

(Or maybe just taken out for an Italian Tune up every now and again.)

Edited 14 December, 20169 yr by Offski

Not sure what they are trying to cure with the skim. I think a warped rotor would need replacing but warped rotors can be caused (or at least used to be caused) by and of the following. A poor break in procedure (garag procedure or the driver hammering the brakes from new once back from the garage) could also mean the contact between the pad and disc wasn't right. I guess that could warrant a skim too.

 

New discs and pads have a break in procedure the last time I did it in when replacing the discs on my partners yaris it was a a couple of moderate braking efforts from 30 to stopped then a few more drop anchor ABS stops from 40 then the same from a higher speed. Needless to say this is usually done by the garage (for one they won't panic when they see a column of smoke coming off your disc!) for safety reasons and it can be quite difficult to find somewhere safe to do it. The instructions for the eight or so full on stops from full speed do specifically say something like 50 or 60 to 10, not stationary. The reason here is the pads and discs will get very hot and holding the brakes on while this hot can warp them.

 

Secondly when driving the car after getting the discs and pads fitted you are supposed to take care to avoid situations where you'll be braking heavily. In other words bigger gaps and taking it easy if you are someone who sits on the speed limits or worse. You have a second opportunity here to knacker the discs if you give them no mechanical sympathy while they bed in. If not warped rotors your pads and discs may not perform as well as they should once bedded in fully.

 

Final opportunity to warp discs is if you regularly slow down from motorway speed or fast traffic to stationary and hold the had still on the foot brake. This again holds the hot pads on the hot discs leaving one bit of the disc to cool differently to the rest and so risk warping due to internal stresses. The hand brake only operates on the rears which has to dissipate significantly less energy (back can't brake as hard as fronts due to weight transfer) and so are generally cooler. Some manufacturers have a completely different braking system for the parking brake (think toyota is one) but I think on the VAG fleet when you have discs at the back it just acts on the pads still.

 

All that said I do wonder about the hill hold brake, and how those systems functions as the last car I had with it on it worked by pressing down hard on the foot brake and releasing when stationary. If this does work on the fronts as well as the rears then I guess they either don't care about the risk of warping or they've designed it out. Modern discs are much much thicker than the original Jag versions and so you would have thought this would reduce the risk of warping. Perhaps it's not as much of an issue as it used to be.

This post discusses the warped disc as a myth, but discusses something that is often referred to as a warped disc which is uneven brake efficency between the pad and the disc through out a revolution.

 

http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

 

In other words if you lightly applied the brakes to slow down you would feel a slight oscillation in the braking effort as the pads grip some bits of the disc better than others.

 

Broadly speaking I think each one of the situations I have described above also describe a situation where this problem can be created. I conceed that I may indeed not be talking about warped rotors at all!

Same thing on this page:

 

http://www.mossmotors.com/SiteGraphics/Pages/brake_discs.html

 

But essentially the advice that I originally advocates still applies.

 

1) Ensure propper initial bed in.

2) Take it easy while the pads go through there extended bed in. I think when all of the discs original machining marks are gone on the wear surface is a good indicator of this.

3) Don't hold the car still on the foot brakes for more than a brief pause.

 

I'll add another:

 

4) Avoid only ever lightly dragging your brakes to slow to a stop.

Edited 16 December, 20169 yr by WesBrooks

This sounds like cheap discs

 

Back in the day if you fitted new discs to a MKIV/V Cortina they seemed to experience judder after a few thousand miles

 

If you skimmed the discs all was well thereafter (until you needed new discs!)

 

probably something to do with heat treatment

Edited 17 December, 20169 yr by bigjohn

Same thing on this page:

 

http://www.mossmotors.com/SiteGraphics/Pages/brake_discs.html

 

But essentially the advice that I originally advocates still applies.

 

1) Ensure propper initial bed in.

2) Take it easy while the pads go through there extended bed in. I think when all of the discs original machining marks are gone on the wear surface is a good indicator of this.

3) Don't hold the car still on the foot brakes for more than a brief pause.

 

I'll add another:

 

4) Avoid only ever lightly dragging your brakes to slow to a stop.

 

 

dont use em....sorted!

Discs still get skimmed where suitable at some establishments because even good quality branded or even OEM which might not be good quality can get scored within just a few hundred miles of being fitted.

Even brand new Demonstrators sitting around for 3 months / 3,000 miles can be red with rust and get a ridge from daily washes and weekly Italian Tune ups.

Taken out on winter roads for 'Road Tests', or a run to the sandwich shop.