Brake heat cracks

[Alex Conway]

Changed the front discs today and notice some significant heat cracks. I realise it's normal to get these in the cyclic loading of the discs, thermally and mechanically.



Is this a normal level of cracking or do I need to work on some extra cooling? Currently just fog light surrounds and liners out. I've got an emergency duct design planned just on case, is this necessary?

Similar both sides.


Regards,
Alex

 

[sonny172cup]

Nice, what discs are they and what pads (compound) was you using?

 

[Bluebeard]

Holy s**t! Never seen cracks that bad before!

 

[Pauleds]

Noticed mine are a bit like that too, had issues with brake fade at Oulton last November using yellowstuff pads and it's probably the reason.
About to fit some AP 4 pots, 300mm rotors with alloy bells. Should stop then!

 

[Owen92]

That's bad. Also believe it's an MOT failure (well it is on HGV anyway) because the cracks cover more than 50% of the width of the disc face. Just something that is worth checking with the car MOT manual.

 

[Alex Conway]

It's a dedicated track car so not too worried about MOT passing.

The discs are brembo HC. It had run pf97 pads for a couple of days and before that a full set of rc6 pads that we managed to run to the backing plate (see picture). Didn't show any cracks though, just some scoring we took out and then bedded them back in. We realised this was properly gash but had been shipped incorrect discs and had a track day he following morning!

They've all looked quiet similar in the past, even when not raped by metal on metal contact. Just thought I'd flag it up. The car still braked fine and disc wear was maybe 1-2mm total thickness - less that 1mm each face.

 

[Cub.]

@MarcJP - you know those heat cracks from your sticky caliper that we talked about.....

 

[Marc.]

Holy s**t! Never seen cracks that bad before!

I think my rears have him beat!

@MarcJP - you know those heat cracks from your sticky caliper that we talked about.....

Yeah I remember - his discs are almost as bad as mine!

 

[Alex Conway]

@MarcJP - you know those heat cracks from your sticky caliper that we talked about.....

Hmm pistons didn't feel stiff by any means when pushing them back

 

[Cub.]

Could you rotate the disc freely? Was it making any noise? I.e. Grinding on application?

It may just be a case of too much heat through yours on track bud. How 'heavy' a braker are you? They are bad, especially after such a short time and the fact you say you bedded the pads in ok.

 

[Alex Conway]

Probably fairly heavy on the brakes! It's only going to get worse as the slicks start working in the summer so I might just get the ducts made up

 

[Cub.]

You may need to look at 4 pots.....

 

[Alex Conway]

You may need to look at 4 pots.....

Probably but I've had a think about it *engineering hat on* and I'll go for ducting, it has got to be a heat management issue and even with four pots the disc will probably still cook

 

[Tony Hunter]

Strange one, as I've never had any trouble at all with mine in the 4yrs of racing?

 

[Alex Conway]

Strange one, as I've never had any trouble at all with mine in the 4yrs of racing?

Tony, do you run deflector plates or just fog light surrounds and wheel arches out?

 

[Tony Hunter]

Fogs out, with the surround trimmed away, and no liners. We tried deflector plates and ducting and stuff, but it just all gets in the way.

Do you hang onto your brakes? It could be the way you are braking, and this wouldn't help the situation.

 

[Alex Conway]

I trail brake aggressively but am normally back on the power before the apex. Not sure how my dad drives, brakes rarely smoke. Always right foot braking so no double pedal dragging.

I brake to put myself through the windshield generally...

 

[Sam@NP]

They are fucked!

What nake of disc was it?

 

[Alex Conway]

Brembo HC with RC6 pads followed by pf97

 

[George@RTR_Parts]

Never seen any like that and I've used them myself and supplied a fair few to plenty of people who track and race their cars

Have you measured the total thickness of them mate?

 

[Alex Conway]

Never seen any like that and I've used them myself and supplied a fair few to plenty of people who track and race their cars

Have you measured the total thickness of them mate?

Nope, less than 3mm thinner than news ones when looking set total width though

 

[George@RTR_Parts]

They come with 24mm new, the minimum thickness for them is 21.8mm

Be interested to know the thickness of those

 

[Pauleds]

The ones on mine were on it when it was bought, probably some cheap crap Motorfactor ones

 

[Alex Conway]

They come with 24mm new, the minimum thickness for them is 21.8mm

Be interested to know the thickness of those

Old discs were in the bin, in fairness I'd say they were on the minimum when they came off. 3mm was with a factor of safety

 

[George@RTR_Parts]

I was going to suggest if they haven't passed it , they were very near the limit of needing changing imo mate

 

[Alex Conway]

We normally swap the fronts each time we do pads, they cost nothing in comparison. Just left on in emergency