Brake drum cracks and causes rollover

[Steve C]

Hi

My car club organised a Supersprint as part of the VW Nationals 2010.

A very respected veteran racer had a rollover caused by what seems to be a new German brake drum cracking.

The driver is fine, just a bit shaken, I will let the photos tell the story.

Steve

2 photos are mine, I nicked one from Dave (STI dub)

[vdubzack]

I cant stop crying!!
I hope that he is OK!
Cast iron is great but does not like shock. There was a guy that I used to hang out with, that dropped his new in box German rotor on the driveway of his garage. No worse for wear except the ding on the edge. but once the brakes were applied after being adjusted. BANG! cracked fron one side to the other. plus I dont think his liberal use of the impact wrench helped either. I asked him does he use a torque wrench but he subcribes to the one more turn method. Please check the torque values on your drums and rotors. With rotors, that can be a major cause of warping, and in some cases can cause that "Super Shimmy" That we all dread. On cast iron, it can lead to cracking expecially on wide five wheels, as the bolt holes are so close to the edge of the area where the most heat is generated. Uneven torque will have uneven expansion and cooling rates. You check the torque on your rod bolts and heads. why not the wheels?

[evilC]

I'm not a fan of hubs and brake drums being cast as one since overstressing one portion can lead to catastrophic failure, which look like what happened here. Separate forged hubs are much better and they can be easier to (more accurately) machined and are much stronger. Its the hubs that take bending forces in the turns and the fulcrum that a wide 5 pattern makes does not help.

Clive