Have I cracked a brake disc?

[MarkCup]

Day to day I have no problem, car stops fine, no noise or vibration, nothing untoward.

When making progress though, after one or two heavy brake applications, I get a noise relative to road speed, a knocking that's only present when on the brakes and it gets louder the longer/harder I'm on them.

Have I cracked a disc?

Don't know much about this sort of thing but if I had a hairline fracture, might it only make itself known when I get some heat into them, hence the noise?

I get no judder or vibration though.

All academic really as I've a new set being fitted this coming Friday...I'm just curious as I've had a good look at them and I can't see anything visibly wrong.

 

[BrianR]

Sounds more like a wheel bearing, Mark.

 

[MarkCup]

If that's so wouldn't I hear something before leaning on and heating up the brakes?

I really would never know of/hear it unless I was pressing on...can/do wheel bearings partially fail so as not to rumble when taking things steady?

 

[BrianR]

Yes, probably. If it is in fact the bearing.

As you use the brakes and heat the whole assembly up, the hub grease will thin and the bearing will become noisy.
When its cold you wont hear it.

 

[msa197]

Brake pins????

Brake fluid??