Looks like a crack in rear brake disc

[windym]

Hi, was going to change the rear discs and pads after Christmas but on closer inspection it looks like there may be a crack or casting fault in the rear right.

Not going to take any chances but what do you guys think, should I be concerned? Also what are the best replacement discs for this z, 2000 1.8i and where to buy.

Thanks Andy

 

[TaffZee]

Yes that looks like a crack, and I would change immediately, Try Euro Parts.

 

[Brian H]

Hi, was going to change the rear discs and pads after Christmas but on closer inspection it looks like there may be a crack or casting fault in the rear right.View attachment 22776 Not going to take any chances but what do you guys think, should I be concerned? Also what are the best replacement discs for this z, 2000 1.8i and where to buy.

Thanks Andy

Are you sure is not a line of brake dust where the pad came to rest, looks very straight for a crack!

 

[windym]

Hi, really not sure, I ran an owl over it and the point snagged in a couple of places but the bottom does look like the shape of the brake pad. I think for peace of mind I will change them, don't want to be out driving worrying wether it is a crack or not.

Andy

 

[jonco]

You could try a dye penetrant check - kits are a bit expensive for a one off test but maybe a local welding/fab shop could help you out.

 

[t-tony]

That's not a crack it's simply a "grab" mark. If you go out on a quiet road and give your brakes a good breasting they will disappear. It's a sign of lightly used brakes! on a car that doesn't do a lot of miles.

Tony.

 

[Redline]

First impression is that it is too ill defined to be a crack. As said earlier, some light braking (forward and reverse) may shift what looks like dust. Just mark the edge of the disk and see if it cleans up or moves.

If it is a crack however it needs changing immediately. You don't need the disk exploding under heavy braking...

 

[t-tony]

I'll just say this in all my working life I have NEVER seen a disc crack like that !!

Tony.

 

[hard top]

You could try a dye penetrant check - kits are a bit expensive for a one off test but maybe a local welding/fab shop could help you out.

MPI now that is a good idea, you should be able to get that done at most machine shops.

​

 

[hard top]

@jonco seen it done out in the field on drill pipe with portable kit, magnetize the object, spray some flux on it, stick a tarpaulin over your head and use a UV light, Bobs your uncle.....

 

[Brian4]

When disc crack there are usually lots of smaller cracks around the disc. As the mark is curved at the bottom it looks like the outline of the brake pad left when it has been parked up.

If you have any worry and for the price of them just change them rather than spend money on NDT test. Have you changed the pads recently? as the mottled area each side of the shiny brake area looks like rusty disc just being polished by the pads, if so you need new discs and pads.

 

[windym]

Hi, cheers guys thanks for the advice going to change them, on closer inspection they look a tad knackered as Brian4 said the pads seem to be polishing rather than stopping. Not surprised really as the car has done on average under 1700 miles a year for the last 5 years. Any suggestions on brake discs is it worth upgrading or do I just keep as standard?

Andy

 

[t-tony]

The only likely chance of a vented disc cracking is when the bridge pieces between the two sides of a vented disc breaks down through corrosion. I did have this happen on my Touareg which resulted in juddering through the brake pedal as the two sides of the disc were compressed during braking. An unpleasant experience, but even so the disc still did not crack. Disc manufacturers state a minimum thickness for their discs to wear down to, but even so corrosion between a vented disc can only be assessed by the eye. I once saw a disc worn so thin on a Talbot Horizon that it sheared of from the hub part of the disc and guess what ? even that one did not crack.

Tony.

 

[t-tony]

Hi, cheers guys thanks for the advice going to change them, on closer inspection they look a tad knackered as Brian4 said the pads seem to be polishing rather than stopping. Not surprised really as the car has done on average under 1700 miles a year for the last 5 years. Any suggestions on brake discs is it worth upgrading or do I just keep as standard?

Andy

If you have a branch of Euro Car Parts near to you they do Pagid discs which have a very good coating which don't rust and keeps a nice look. Also Andrew Page now do Mintex discs in coated form too. Re the mileage, see my first post .

Tony.

 

[t-tony]

Just to add to this, unless you intend using your car more and using the brakes hard enough to keep the discs clean you would be wasting money on upgrading from standard in my humble opinion.

Tony.

 

[zedonist]

That's not a crack it's simply a "grab" mark. If you go out on a quiet road and give your brakes a good breasting they will disappear. It's a sign of lightly used brakes! on a car that doesn't do a lot of miles.

Tony.

Can you explain the Breasting process please Tony

 

[windym]

Just to add to this, unless you intend using your car more and using the brakes hard enough to keep the discs clean you would be wasting money on upgrading from standard in my humble opinion.

Tony.

Hi thanks, I do intend to use this all year round, the former owner used this car in the summer it seems, by the milage on the MOT log. I have only had it a short while now and have loved every minute of owning/driving it. So at the mo just going over the car and sorting out what needs to be done, in order to keep it in good shape. Also sorting out and changing or adding what does not need to be done but puts a big inane grin on my face.

Andy

 

[t-tony]

OOPS! sorry mate, bloody iPad........................... please delete the "r" when reading that post.
I feel a right tit now.

Tony.

 

[t-tony]

Hi thanks, I do intend to use this all year round, the former owner used this car in the summer it seems, by the milage on the MOT log. I have only had it a short while now and have loved every minute of owning/driving it. So at the mo just going over the car and sorting out what needs to be done, in order to keep it in good shape. Also sorting out and changing or adding what does not need to be done but puts a big inane grin on my face.

Andy

Absolutely Andy, wasn't meaning to preach or anything. The discs I mentioned are very good I have Pagid ones on my Z3. Excellent items. They also take a coat of paint really well too if you intend applying some paint to the brakes at the same time. Re the grin factor - just been out with a mate to show him how quick my Z4 is, I think he likes it. Good luck with all the things you want to do.

Tony.

 

[hard top]

Haha Tony......"Breasting process"

rather than spend money on NDT test.

If you know where to go, it will not cost you anything......