carreracoupe997

Zimmerman drilled rotor failure, Road Atlanta. Inspected prior to running with NO cracks...none. Rotor exploded on 2nd 20 minute run of the day without warning. Calipers were Big Blacks and pads were Hawk Blue. Why cup cars used drilled is beyond me. Driver was air-flighted to hospital. Concussion, broken elbow and sore. He is fine now Thank God.

carreracoupe997

My bad.

TheOtherEric

So non-drilled rotors have never ever failed? Not even once? Prove it's true and I'll follow your advice.

Geoffrey

We've seen issues with OEM replacement rotors and premature failure. Even the rotors with identical markings to the Porsche ones. One of the things we found is that on a non Porsche OEM rotor, the grinding for balancing is more agressive and takes more material out which leaves the rotor thin at that point. I believe that the OEMs produce say 100 rotors and Porsche looks at all of them and the ones that pass their specification are branded Porsche and the ones that don't are sold as OEM. They are the same rotors, but just not as good quality due to the balancing and reslutling grinding.

carreracoupe997

The cracks will appear STARTING from within the hole. I would never say a solid or vented disc will not fail, its just far less likely, that's all.

NJcroc

Should be more like what makes a cheaper rotor cheaper thread than dont use crossdrilled rotors.

If indeed thier were no cracks in the rotor at all then they were most likely either to thin or had a manufacturing problem

jgrant

Seems to be a rather inflammatory, lack-of-detail post, that is trying to draw an illogical conclusion.

I doubt very much that the reason that happened was because the rotors were drilled. If that were the only reason, then there'd be a hell of a lot of carnage on the tracks, as a lot of cars/teams use drilled rotors without any adverse effects.

$0.02


And, for what it's worth, we don't run drilled rotors on our cup car.


That being said, I'm sorry to hear it happened, and I hope the driver recovers quickly and completely, and is back out on the track soon.

Bull

Seems like this should be titled "why not to use a Porsche 944" given the logic leap here.

carreracoupe997

Here is the rotor after picking up the pieces left on the track. We just put the largest pieces on the drivers floor board.

VERBOTN

Was this DE or Race? The only reason I ask is that I have been a huge proponent of safety gear at all levels not just race. A sudden mechanical does not know the difference.

jgrant

From what I can see, there appears to be quite the raised lip on the outside of those rotors. If I had to guess, without being able to look at them in person, I'd say that the rotors were too thin. Nothing to do with them being drilled.

Any close-up pics of the rotors?

carreracoupe997

It was at a BMWCCA DE. Sorry no close ups of rotor but I can assure you the photo is deceiving because I held these rotor pieces in my hand. The rotors were almost new and did not have a raised lip, ie: too thin.

sjanes

I had a student in a Dodge Stealth with stock (non-drilled) rotors that failed. Left front rotor exploded into bits in the hardest braking zone at the track. Luckily we didn't crash.

FWIW: I used to use slotted Coleman rotors (S4 front calipers) and would go through two sets/summer due to cracks in the rotors. I switched to drilled Brembo rotors and they now last almost 2 years before they need to be replaced. Rotor quality is more important than slotted/drilled IMHO.

Cory M

take some clear close-up pictures of the fracture surfaces and post them up, pictures of a crashed car tell us nothing

don't let anything touch the fracture surfaces, or try to put the two pices together at the crack line, or it screw up the surface and make it hard to see the type of failure

Oddjob

What p/n were these rotors? 965 351 041/42 (968 M030), 043/44 (964T), 045/46 (964 3.6T) - or other?

Brake kit came from where? Calipers mounted direct on M030 spindles, or using caliper adapter on non-M030 spindles?

The cracked edges the rotor chuncks shown do not appear to follow the drilled holes or the hole pattern - although it is hard to know where the first crack started that caused the initial separation leading to catastrophic failure. As Cory asked, more pics of the pieces may be helpful.

Would be worthwhile to have the other rotor and the broken rotor parts tested/x-rayed. Im not sure what the best testing method would be to determine a casting flaw or metallurgical problem - but sure seems like the driver/owner should look for a failure mode on this.