[mark_cathy]

Hi, after a driver training day on the weekend where I discoved race level braking on a race track, as opposed to my previous outings where I was with hindsight rather gentle, my MO30 front rotors have hairline cracks, maybe 5mm long, emanating from some of the drilled holes. Though they are very small wondering two things.



1: Is this a safety issue to worry about, or generally ok?

2: Do i need to cool down better, or is this normal when you are really using them on a track in a race car braking type fashion. The discs were nearly new, but bedded in. They are not warped at all, just the above issue is evident.



Tks



Mark



(would post pics, but wife went os today with our camera)

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[Eric_K]

The small cracks are normal and typically not a problem. You want to watch that they don't get to the outside edge of the rotor. Harder and hotter the brakes are used, the quicker they appear. You may want to investigate some brake cooling and make sure you are not now over braking.

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[flash]

you could also install a different brake bias valve to set more to the rear, thereby reducing the heat on the front brakes

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[Jason Judd]

As Eric said, the small cracks are not such a problem...



Unless they either run out to the edge of your rotor, or, if they start playing 'connect the dots'...That is, if they start to run from hole to hole, then you'll have to watch them much more closely.



I'm trying an experiment with 'Frozen Rotors' right now...they seem to be holding up very well, and show no heat/stress cracking after 2 events.



Jason

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[flash]

unless they have started freezing them right out of the mold, while they are still red hot, from the physics involved, frozen rotors should last a bit longer on a street car, albeit at the expense of some braking (less friction equals less braking) - i've talked directly with some of the manufacturers of these things, and they have confirmed this - they are very careful not to talk about braking distances and such in their ads, and only about rotor life



on a race car, you probably won't see much of a change - the first time you get them up to the much higher temps you see, the surface treatment of the freezing is essentially gone - it probably helps with break-in though, as the temps would climb more slowly at first, increasing the chances of a more even cooking



the heat stress of the drilled areas might be reduced for a longer period though, since that surface never gets touched directly, and is the coolest place on the rotor - interesting idea



let us know what happens



i'd love to see some empirical data on these things - so far, all i see is hype

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