Got the dreaded cracks appearing

[JDS]

Not sure to be honest, but their concern was the difference of temperature across the disc thickness, solid or vented, causing different rates of expansion. The way he explained it, you get a wave of heat, and therefore differing expansion, going through the material thickness each time you apply the brakes.

Heating and cooling the disc in an oven slowly, doesn’t cause the same issues.

[scoob]

that is a really interesting site stevengreen, did you look at all the other stuff they do?

[stevegreen]

Some - anything catch your eye?

[scoob]

water mist/spray onto intercoolers

[stevegreen]

thought it might be that one!

[scoob]

is it popcorn time?

[stevegreen]

lunchtime - soup and sandwich…

[Porkie]

@Boothy

How must the Porsche discs get on? They are literally covered in holes.

Rubbish! I could crack a set of brand new 997turbo discs in ONE trackday…

[Podger]

@Porkie

[quote=Boothy]How must the Porsche discs get on? They are literally covered in holes.

Rubbish! I could crack a set of brand new 997turbo discs in ONE trackday… [/quote]

Another example of inferior German manufacture ?? or do they buy the castings that are made in Dudlaay ??

[scoob]

@JDS

From discussing this with AP, the biggest problem they face is uneven heating. The temperature of the disc friction surface rises very quickly to 600-700 degrees, while inner surface has an amount of cooling air presented to it. It appears to be this that causes the problem over repeated cycles, rather than the temperature itself.

just an update…no cracks on inner surface…only 4 or 5 holes with small cracks on the outer surface. As said it is something I have been expecting and looking out for due to you lot making me aware of the problem. So gonna stick with it and change discs when pads are next changed… Sorry Dave may be next month : )

[seriouslylotus]

[quote=scoob]
just an update…no cracks on inner surface…only 4 or 5 holes with small cracks on the outer surface. As said it is something I have been expecting and looking out for due to you lot making me aware of the problem. So gonna stick with it and change discs when pads are next changed… Sorry Dave may be next month : ) [/quote]
No apologies necessary, Its alway good when anyone has good fortune and saves the cash for another day!!

Right kids no food tonight - sorry

[scoob]

Dave did you get my email?
I need to know what I am in for.

[AndyD]

@JDS

From discussing this with AP, the biggest problem they face is uneven heating. The temperature of the disc friction surface rises very quickly to 600-700 degrees, while inner surface has an amount of cooling air presented to it. It appears to be this that causes the problem over repeated cycles, rather than the temperature itself.

Intertesting

In a previous life we sold moulds for vinyl record production ( for those not old enough this was BCD )
These moulds looked a little like a brake disk.
Those had a hard life as steam would be introduced into the mould to help the PVC flow into the grooves and then water would be injected to rapid cool it. You can guess what happened to them after a few hundred thousand cycles … yeah they cracked.

[seriouslylotus]

[quote=scoob]Dave did you get my email?
I need to know what I am in for.
[/quote]

Yeah
Will send one back later this evening
Sorry…