Why Not To Use Drilled Rotors
03-06-2009, 06:21 PM
#16
Three Wheelin'
This is why it pays to check your rotors between EVERY session! This last weekend one of the rotors on my GT3 cracked completely through between sessions. It would have likely come apart on me if I tried to go back out on track.
03-06-2009, 06:47 PM
#17
Rennlist Member
Ive been using drilled zimmerman rotors for 12 years now with out any issues. yes, the crack after about half of our racing season (about 7 races). I usually change them out when the cracks meet the edge. they seem very strong and durable and havent seen any problem. the cracks dont propagate that fast either so usually if i have bad cracking, it will finish out the weekend and then i change them out. any pics of the rotor and cause of its falure? was it at the rotor or hub area??
with big blacks, we must be talking about the 935T rotors as well. (964 turbo late model)
mk
with big blacks, we must be talking about the 935T rotors as well. (964 turbo late model)
mk
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.
03-06-2009, 06:52 PM
#18
Rennlist Member
GREAT EYE! Yes, this much material missing from the outside edge, would be the main reason for the failure. (unless it happened during the crash)
when mine are cracked to the edge, there is NO wear to be measured on the rotor. (i.e. never a lip)
Mk
when mine are cracked to the edge, there is NO wear to be measured on the rotor. (i.e. never a lip)
Mk
03-06-2009, 06:58 PM
#19
Rennlist Member
I guess it looks like the rotor came apart from the hub at that point. (that gave the illusion of a lip)
The are 965T rotors as you can see the vent holes being 5 and 4 in number on the rows. I didnt think zimmerman even made this rotor. the only ones I could get on my 928 up grade with S4 calipers using spacers, was the porsche oem rotors cast hole version.
very strange failure, especially with non -cracked holes . defective rotors possibly!
mk
The are 965T rotors as you can see the vent holes being 5 and 4 in number on the rows. I didnt think zimmerman even made this rotor. the only ones I could get on my 928 up grade with S4 calipers using spacers, was the porsche oem rotors cast hole version.
very strange failure, especially with non -cracked holes . defective rotors possibly!
mk
some 944's are ok 
03-06-2009, 08:34 PM
#21
Rennlist Member
Wow. That's scary. The guy next to me in the garage at Pocono had a 951 with drilled rotors. One developed a crack on the outer edge that he could start to feel through the pedal. Called it a day. Don't know who made the rotors.
03-06-2009, 08:54 PM
#22
Rennlist Member
03-06-2009, 09:16 PM
#23
Rennlist Member
I have seen brand new cross drilled rotors explode like this when used with new Hawk Blues. It is possible that they were not bedded, and the extreme nature of the pads and rough rotor surface just put too much heat in too fast. I'm not a fan of cross drilled rotors, but with my 993, they were extremely good, if short lived when used with an aggressive pad. But, as Eric said, it could happen with any rotor
03-06-2009, 09:24 PM
#25
Rennlist Member
could ABS be a factor?
It is hard to imagine what would cause this failure except defective metalurgy.
warped rotor would cause uneven stress on the rotor and break it eventually, especially risky if we are talking one piece construction, as we are here.
Was there any warning at all? vibration?
mk
It is hard to imagine what would cause this failure except defective metalurgy.
warped rotor would cause uneven stress on the rotor and break it eventually, especially risky if we are talking one piece construction, as we are here.
Was there any warning at all? vibration?
mk
03-06-2009, 09:28 PM
#26
Rennlist Member
Ive been using drilled zimmerman rotors for 12 years now with out any issues. yes, the crack after about half of our racing season (about 7 races). I usually change them out when the cracks meet the edge. they seem very strong and durable and havent seen any problem. the cracks dont propagate that fast either so usually if i have bad cracking, it will finish out the weekend and then i change them out. any pics of the rotor and cause of its falure? was it at the rotor or hub area??
with big blacks, we must be talking about the 935T rotors as well. (964 turbo late model)
mk
with big blacks, we must be talking about the 935T rotors as well. (964 turbo late model)
mk
03-06-2009, 09:41 PM
#27
Drifting
I was at Road Atlanta Today running in this instructor group. I think this is an old picture from almost 2 years ago. There weren't any incidents besides a couple spins.
I've heard this story and I've seen the picture o the interior too. But it was from a cracked rotor; just not today.
I've heard this story and I've seen the picture o the interior too. But it was from a cracked rotor; just not today.
03-07-2009, 01:49 PM
#30
Racer
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007DT
I was at Road Atlanta Today running in this instructor group. I think this is an old picture from almost 2 years ago. There weren't any incidents besides a couple spins.
I've heard this story and I've seen the picture o the interior too. But it was from a cracked rotor; just not today.
I've heard this story and I've seen the picture o the interior too. But it was from a cracked rotor; just not today.