Trackdays, don't forget to check your discs carefully ...

[ChrisW.]

I thought that these might just do one more trackday ... until I looked again.

If you enlarge the image towards the top left and notice where the pads have swept a light film of corrosion, this disc is cracked to the edge and another crack from this is clearly seen extending well beyond the 4 to 5mm length which I felt was acceptable ...

[993rsr]

I had this on a 993rs out of interest put the disc on a surface grinder the crack did not penetrate the rotor it was only on the surface .

[Digga]

993rsr said:

I had this on a 993rs out of interest put the disc on a surface grinder the crack did not penetrate the rotor it was only on the surface .

Brittleness on heat affected zone.

The S-shaped grooves on Alcons tend to withstand better than the OEM holes. I reckon a bigger radius on the holes would’ve helped too.

[Redarress]

Always check crack with an ultraviolet crack testing system. Rocol make a two pack aerosol set for this purpose. Sometimes the machining /grinding hides the cracks from the naked eye. It’s called a Dye Pen test. We carry it out in our workshop on metal Components that are strength critical

Edited by Redarress on Friday 21st April 23:06

[Mumsn3t]

That shouldn't do another track day but it's safe to drive. I cracked a disc almost from edge to edge and drove my m3 home from spa many many years ago. Couldn't believe how strong it was. I wouldn't do it now, but being young, dumb and skint I had no choice.

[ChrisW.]

Thanks for the feedback on that ...

I once made a mercy dash from Spa with a friend to pick up a new pair of front discs and pads for his Z06 ...

After a fast session he had parked up in his garage but when he needed to move the car slightly found that it jammed as-if the handbrake had sprung on ... one of the front discs had broken completely, split so that the whole disc was dislocated by a couple of mm, the raised edge jamming on the brake pad material ...

A very lucky escape, and thanks to a kind GT3 Cup car owner and his techies the Z06 was fettled before the circuit was locked up for the night.

But imagine what could have happened on circuit ??? Maybe not ...