Cracks in brake disc

[Loom]

How does a brake disc crack like this? It's the rear disc.

Front of disc:





Back of disc:



Handbrake shoe:

 

[Philip Foglar]

Heat! Also it looks like the disk is really thin now! Solid non-ventilated disk?

 

[calypso]

Well if it's under minimum thickness, then the reason is pretty obvious.

 

[netercol]

heat.. over-use of brakes i think bmw calls it.. :=):

 

[abmi0000]

Continuous use of brakes when there is shudder can also cause that. But as the other guys have stated, heat is a big culprit

 

[moranor@axis]

they look very thin... pushing them hard when they thin will do the job...

 

[Mr Occo]

Eish!

 

[Raybimmer]

IMHO if you go for a fast drive and use the brakes a lot the discs heat up , now you brake to a stop and stand with the pads against the disc . This creats a hot spot as it is not being cooled by the air . These also tend to get hard and later cause shudder as the disc wears more where it is soft .

If your brakes are hot and you hit water they can crack as well , ask any guy who has welded steel and quickly cooled it off in water , in can crack at the weld where it was hot .

Thinner discs will crack easier due also to enequal frequencies ( vibrations ) in the material .( That is where matel fatigue in aeroplanes plays a critical role ).