Can someone tell me how I can tell whether my discs need replacing.

Got a 2001 TDi estate with 85000 on the clock. The brakes still work fine but there a slight ridges (circumfrential) and a bit of a shelf on the outer edge where the disc is starting to wear down.

Is there a minimum thickness that the discs need to be? If so how do i measure this?

The pads still have about 6mm of pad left on them, I assume these won't need replacing?

The front and rear brakes are all in a similar condition.

Thanks for any help

andrew

6mm of pads is fine.

You would expect to get a bit of a lip on the edge of the disks. I have been known to take an angle grinder to mine in the past. There is a min thickness, not sure what it is. I tend to find the standard disks warp rather than wear out.

Min thickness as follows:

Petrol 19mm except 1.8 litre which is 23mm (AGN is exception 19mm)

Diesel 19mm (ASZ is exception 23mm)

Measure disc thickness on the polished swept area, not on the rust on the very edge.

For anyone interested - very recently Aldi was selling a digital caliper for about £7 - does internal /external + depth . Has xero facility ,so could be used with spacers to check disk .Might be uefull as lots of tyre places (and MOT men ) seem to associate the lip with wear .Never in any of my cars had disc wear probs ,unless the Furby diesel is an exception .

thanks for the replies so far.

The lip at the outside is about 1mm, so to save me finding some callipers, what is the starting thickness of the discs?

Looks like the brakes can wait - think I'll have to put my time and effort into getting the rear beam bushes sorted

Min 19mm, New 22mm

Min 23mm, New 25mm

lots of tyre places (and MOT men ) seem to associate the lip with wear .

Which is just nonsense; discs that are a couple of months old can often have a visible rust (not wear) lip on them.

What would be the min for a MK1 vRS. Hope there's a bit of life left on them as then just need some good pads, need and want better brakes. Just aint got the money

I have just been told that my 04 octy 52000 miles has "Very worn Discs" and my wifes Ford Ka with 21.000 miles has had a similar report from different garages.

I know discs will wear eventually but I thought it was the disc that wore the pads out and not vice versa! I rather suspect that virtually every car on the road over three years old has a degree of "Lipping" as the MOT tester calls it but it stands to sense that the disc is going to get some wear on its swept surface and non where the pads dont contact the disc.

Is this phenomenon connected with asbestos free sintered pads or is it just a new trendy potential failure point that the testers have been updated about?? Im all for safe brakes believe me but at times I just get a bit synical.

Never replace discs without replacing pads aswell

I have just been told that my 04 octy 52000 miles has "Very worn Discs" and my wifes Ford Ka with 21.000 miles has had a similar report from different garages.

I know discs will wear eventually but I thought it was the disc that wore the pads out and not vice versa! I rather suspect that virtually every car on the road over three years old has a degree of "Lipping" as the MOT tester calls it but it stands to sense that the disc is going to get some wear on its swept surface and non where the pads dont contact the disc.

Is this phenomenon connected with asbestos free sintered pads or is it just a new trendy potential failure point that the testers have been updated about?? Im all for safe brakes believe me but at times I just get a bit synical.

Firstly, disc thickness is not part of the MOT, but should be part of a service.

Secondly, asbestos-free pads do wear brakes much more heavily than old asbestos pads did. You should probably reckon on needing new discs about every other set of pads.

Never replace discs without replacing pads aswell

Absol-fragging-lutely!!

For anyone interested - very recently Aldi was selling a digital caliper for about �7 - does internal /external + depth . Has xero facility ,so could be used with spacers to check disk .Might be uefull as lots of tyre places (and MOT men ) seem to associate the lip with wear .Never in any of my cars had disc wear probs ,unless the Furby diesel is an exception .

i bought one- cant fault it, fantastic bit of kit

I suspect this problem is in part down to metallurgical control, or lack of it, when these discs are cast. This explains why some people can get decent mileages and other far less less so. I will now sit back and see who wants the argue this point

I'm just changing the brake pads on my 1.9 TDI (asz) Octy and have between 21,5 and 22mm on the brake discs. They were new about 20,000km ago and the brake pads are almost not worn at all.

You might be asking why are you changing brake pads, because im sick of having dirty rims the whole time and have bought ATE carbon brake pads to combat the problem and to not wear down the discs as fast.

Can I still use the discs even though they are below the minimum of 23mm? I'm assuming the carbon brake pads will not wear the disc down at all. 

What would be the potential problems if I do?

 

Cheers

Fraser

I suspect this problem is in part down to metallurgical control, or lack of it, when these discs are cast. This explains why some people can get decent mileages and other far less less so. I will now sit back and see who wants the argue this point

Well discs are made by many different company's and will use different grades of steel. 

The biggest factor for brake disc and pad wear is the user.

I'm just changing the brake pads on my 1.9 TDI (asz) Octy and have between 21,5 and 22mm on the brake discs. They were new about 20,000km ago and the brake pads are almost not worn at all.

You might be asking why are you changing brake pads, because im sick of having dirty rims the whole time and have bought ATE carbon brake pads to combat the problem and to not wear down the discs as fast.

Can I still use the discs even though they are below the minimum of 23mm? I'm assuming the carbon brake pads will not wear the disc down at all. 

What would be the potential problems if I do?

 

Cheers

Fraser

With the price of carbon pads, I'd change the discs now rather than needing to throw away hardly worn pads when the discs start coming apart. If you look inside one of the ventilation slots in the edge of the disc, you'll can see how thick the remaining swept area isn't, and the less of that you have the hotter the discs will get doing stuff like descending passes. Discs don't just wear away, but wear so far and then suddenly fail.

Never replace discs without replacing pads as well

 

What about vise versa? 

 

I installed a few month ago new brake pads in all 4 corner and I think I going to replace the rotor disc now.

 

Any advise?

 

THX,

 

Isaac