Cracked B7RS4 disks (on RS6 calipers)

[viperbl]

Guys,

I got the RS6 callipers and decided to go for the B7 RS4 drilled disks (instead of RS6 disks). I have been using the OEM black pagid pads and on my 3rd set now (probably disks have covered 6k ish now)

As you can see there are some big cracks appearing... now, I have been very happy with these disks, they have done the job, never had any fade or warping etc, but obviously the cracks at 6k is annoying...

I wonder if these have appeared because of one of the following.

I did not clean out the holes and they filled up with brake dust, it was packed in tightly, I had to drill it out.

So,
1) Brake dust expands quicker than the disks, so can create undue stress and cracks?
2) In drilling them out I have caused stress/stripped the side of the holes and caused premature cracking?
3) The heat build up with my usage was just too much and over 6k it has cracked?

Main reason for asking this, if it’s because of 1 or 2 I will go ahead and buy the B7 disks again, if its because of 3, I will probably try the RS6 disks this time around...

More Pics here

[CliveH]

Looks pretty severe to me after 6k!

Mine are still looking good after 12k, but then I dont drive it like you...

[Doug_S2]

how much of a lip is on the discs

[MarkB]

I got the RS6 callipers and decided to go for the B7 RS4 drilled disks (instead of RS6 disks). I have been using the OEM black pagid pads and on my 3rd set now (probably disks have covered 6k ish now)

Mate, you are an ANIMAL!

[ChipHazzard]

how much of a lip is on the discs

I'd say those disc's have more lip than Mick Jagger .............

[MCB]

Have to agree with Mark, Rich you are an animal.

When you drilled them out did you countersink the holes - a small chamfer to remove the sharp edge?

Could be down to maintenance, obviously as you know doubt realise keeping the holes clear would of definitely helped and as Doug mentioned have these now reached the wear limit are you looking for new discs?

[DavidT]

3 sets of pads and 6k miles - I would say you have done very well out of them mate. I judge this mostly on the vids you've posted.

They look OK for now to me, I'd guess you'd get another couple of thousand out of them.

After each extreme use, you should clean out the holes and pressure wash the vanes too. It will help them last longer.

[viperbl]

how much of a lip is on the discs

Just checked, they dont seem that bad, maybe 2mm, but it a lot more tapper into the disk as opposed to the rears, which has quick an sharp lip.

unfortuantly, I did not countersink the holes after drilling ...

As I said, I did not look after them when I first got the disks (due to never having drillied and not realising I had to clean!) and then drilling, it seemed pretty hard on them ... now, as David says I just pressure wash them, and as long as I keep on it, the dust does not get a chance to compact.

I mean, I recon I will use these disks until the pads are finished (or they get really bad), but what does everyone recon, same B7 disks or go for RS6 disks, with the slight modification to fit them?

[MCB]

Rich the discs will have a wear limit and would be good to check this. And I reckon the floating disc is the better option for the Schumacher's among us!

[viperbl]

ahhh, is the RS6 disk not floating then Paul???? I think I will stick with RS4 B7 disk in the case, and see how I get on with taking proper care of them from day one ...

I think I will invest in some of those pincer things to measure the disks, thats what I need is it not?

[ChipHazzard]

Viper with a lip like that your better off getting a micrometer rather the trying to use pincers or calipers

[viperbl]

Micrometer,

Like This or This

am I better with a digital one?? there are some cheaper analog ones around as well ...

[ChipHazzard]

I'd say the choice is your's at the end of the day, but a digital one is probably easier to read

[MarkB]

With the way you use the brakes might be worth looking at fitted the ceramic setup off the B7?

[viperbl]

Really? I did not know about this??!! (I can feel a massive price tag here!!! )

Can I use those disks the RS6 Calipers??