Brake discs

[Ant94]

I’ve put a deposit down on a Z4 having test driven it yesterday. It has been through its used car check at Group 1 BMW and has got MOT and valet before I can collect.
Everything was in great condition but someone advised to check brake discs for lipping while I was there. I did feel a slight edge to the first disc I touched as I moved from the central part and rubbed my finger to the very edge. As I checked each wheel afterwards I felt exactly the same, which made me think this was quite normal as it would be unlikely each disc on the car would have the same ‘lip’ if it was a form of damage from brake pad issues.

Can anyone confirm whether this is something to worry about and perhaps mention to them before they send in to MOT so they can check?

 

[brillomaster]

They will check mininum thickness of discs as part of an mot, yes. But a small lip is likely just fine.

Id be more concerned to check the thickness of brake pads, likely go through 3-4 sets of brake pads before youd need new discs.

 

[Ant94]

They will check mininum thickness of discs as part of an mot, yes. But a small lip is likely just fine.

Id be more concerned to check the thickness of brake pads, likely go through 3-4 sets of brake pads before youd need new discs.

Brake pads looked pretty new, as well as the Pilot Sport 5 tyres looking like a fairly new set! Good to know about the slight lip as I was worried having remembered I forgot to mention this to them.

 

[Beerman]

They will check mininum thickness of discs as part of an mot, yes. But a small lip is likely just fine.

Id be more concerned to check the thickness of brake pads, likely go through 3-4 sets of brake pads before youd need new discs.

The manufacturer's minimum thickness guideline is not an MOT failure.

If you buy an AUC from BMW it should be part of their checks. However, I've seen them provide false measurements and change the minimum thickness dimension in order to pass discs that should be replaced as per AUC standards.

I think two sets of pads for a set of discs is more realistic.

A used car is always going to have wear and tear. There is nothing unusual about a small lip and the dealer won't change the discs unless they are knackered.

 

[deltasierra]

2 sets of pads is all you’re to get on discs on the front of a G29, thankfully replacement is not a main dealer task an experienced DIY or decent independant can do the work

 

[martin3]

Small lip on the disc edge is totally normal – it's just where pads don’t contact. As long as discs aren’t below BMW's wear limit and there’s no vibration or scoring, it’s fine. Since you’re buying from Group 1, they should have checked it, but worth asking for measurements.

On my G29, front discs needed replacing just after second set of pads – typical for these. If pads look fresh and discs aren’t grooved, I’d just enjoy the drive and keep an eye on them later.