exploded brake rotors due to cracks

[masraum]

I know I've seen a handful of pics on the board of brakes that failed catastrophically (usually at the track). I think they've all been drilled rotors, but I can find the threads any where. Can any one point me to the pics or threads with pics?

[Steve@Rennsport]

Steve:

Exploding rotors is all about excessive heat; not simply due to rotor construction and design.

Just watch some Nextel Cup racing where this is not uncommon and they all use some kind of slotted or J-hook rotors.

[masraum]

Thanks Steve. Do you think that drilled rotors combined with the heat from track driving would make this more of an issue than solid rotors (not drilled, but vented) under the same track conditions or does it not really come into play. I was thinking that drilled slotted rotors would enable the proper conditions to exist including creating weak spots in the rotors.

I highly value your expertise and opinion.

[Steve@Rennsport]

You are quite welcome,...

Without question, if your peak brake temps are quite high, then a drilled rotor will be less durable than a slotted one since the former will be prone to crack beyond the norm.

Personally, I do not like the practice of using drilled or slotted small (280mm) rotors when hard track use is anticipated. Its not difficult to get 1100-1200deg F peak rotor temps when using race pads and those smaller rotors do not take that for long. You can see this for yourself by using temperature indicating paints on the outer edge of the rotor,...

[HelmetHead]

Masraum....Howdy neighbor

You might want to read this thread regarding heat displacement and holes in rotors.

Holes in rotors??? Not good!!!!

Good Luck.
HelmetHead

[aj88cab]

Steve

Here is a brief photo history of a set of x-drilled Zimmerman rotors I had installed on my '88 Carrera Cab.

6/2004 - Just finshed front end rebuild, they will never look better.


10/2005 - 16 months and 6 DE weekends later.


I watched them very closely and then....

9/2006 - 27 months and 11 DE weekends (total - from new) - we have TOAST..


The cracking only happened on one side of one rotor. Specifically the outside surface of the passenger side rotor. After looking a bit more closely I noticed that the rotor surface thickness was not consistant on the problem rotor. (see photo below) You can see where the crack goes completely through the rotor surface on the lower right. Obviously the thinner material on the outside surface could not dissapate the heat as well and resulted in the cracking. I can't say if this is a common manufacturing error. The current set of rotors I have installed has consistant thickness on all surfaces. No doubt this caused the cracking problems on this rotor and I would bet that many of the cracked x-drilled rotors out there had this same issue. So I now check and will return the rotors if they have this problem.


Andrew

[Bill Verburg]

You do realise that none of the rotors for n/a 911 or 964(other than the RoW RS) were ever designed to have holes.

There is a huge difference between them and 930, 965, 964RS, 993 and 996 rotors that were designed from day 1 to have holes. No one should be in the least surprised that they crack.

Solid can fall apart as well



All rotors and pads are wear items.

[Steve@Rennsport]

Hi Andrew:

Nice pictorial chronology and good testimony about the effects of drilling a rotor that never should be,...

Bill's excellent pictures show the effects of high heat on rotors never designed for those temperatures. Those images represent why people need to upgrade brakes on a track car,......

[DanielDudley]

WHen one side of a rotor wears faster than the other, it usually signals a sticking piston, IMO. Not that this makes drilled rotors any better for racing. Sticking pistons will make your brake temps. skyrocket.

[aj88cab]

Daniel,

I couldn't agree with you more. However, in this instance it wasn't a case of uneven wear. The rotor was manufacturered with one side too thin. If you look at the photo you can even see the inboard plate is acutally wider than both plates on the good rotor (on left in the photo.) For comparison look at the good rotor, both sides of the rotor are the same thickness. I can't really say if it was a casting or machining error (maybe a bit of both).

Thanks,
Andrew