Is it safe to track these rotors?
11-29-2002, 10:14 PM
#11
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The myth about machined rotors cracking more than cast drilled rotors is exactly that, a myth. There is a long article written by one of the Brembo techs that even states.
Basically, the thermal cycling a rotor goes through from track use, is too much for a 1 piece drilled rotor to handle. The drills are the first place the stress cracks will start to appear. From there its only a matter of time. I have tracked my car have gone through a couple sets of rotors without any cracks. I believe the pad compound also has something to do with this. I was running Hawk Blues. Even though these are extremely aggressive and extremely unfriendly to the rotors, they never cracked, they just wore down quickly.
My buddy cracked his non drilled rotors that same day using Panther pads.
Basically, the thermal cycling a rotor goes through from track use, is too much for a 1 piece drilled rotor to handle. The drills are the first place the stress cracks will start to appear. From there its only a matter of time. I have tracked my car have gone through a couple sets of rotors without any cracks. I believe the pad compound also has something to do with this. I was running Hawk Blues. Even though these are extremely aggressive and extremely unfriendly to the rotors, they never cracked, they just wore down quickly.
My buddy cracked his non drilled rotors that same day using Panther pads.
12-02-2002, 08:27 PM
#12
Luis my friend...sorry to here about your misfortune!
Remove the rotors from service immediately. The fear here is not thermal cycling but having your rotor hit a resonant frequency under braking (i.e. vibration). This can propogate the noted cracks almost instantaneously. The rotors pictured are clearly cast and cast crossholes can have a very long and happy life on the track and elsewhere. Be they Spoon or another manufacturer they either missed the temper requirement at the casting level or were not adequately stress relieved after machining. The reason you don't want to drill into a finished rotor is simply that this process creates localized heat which anneals the parent metal (i.e. softens it) and creates a stress riser on which cracks can form. A problem in "cheap rotors" is that even after the holes are cast in they countersink them. Usually not enough heat to anneal is imparted but it's iffy. In your case the holes are cast and the countersinks are wrought (i.e. as cast).......all is good. If you are sure they are from a reputable manufacturer then they were not handled correctly from a thermal stand point during manufacture and the manufacturer..even Spoon...should willingly replace them. If you bought them off the web as "Spoon" then you may also be dealing with an inferior grade of material which could not take the thermal cycle to begin with.
Utah
Remove the rotors from service immediately. The fear here is not thermal cycling but having your rotor hit a resonant frequency under braking (i.e. vibration). This can propogate the noted cracks almost instantaneously. The rotors pictured are clearly cast and cast crossholes can have a very long and happy life on the track and elsewhere. Be they Spoon or another manufacturer they either missed the temper requirement at the casting level or were not adequately stress relieved after machining. The reason you don't want to drill into a finished rotor is simply that this process creates localized heat which anneals the parent metal (i.e. softens it) and creates a stress riser on which cracks can form. A problem in "cheap rotors" is that even after the holes are cast in they countersink them. Usually not enough heat to anneal is imparted but it's iffy. In your case the holes are cast and the countersinks are wrought (i.e. as cast).......all is good. If you are sure they are from a reputable manufacturer then they were not handled correctly from a thermal stand point during manufacture and the manufacturer..even Spoon...should willingly replace them. If you bought them off the web as "Spoon" then you may also be dealing with an inferior grade of material which could not take the thermal cycle to begin with.
Utah
12-03-2002, 01:36 AM
#13
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Thanks Utah... They're definitely from Spoon, but it's been over a year so I doubt they'll warrant the rotors.
I'm having them off the car and take some additional pictures and see what they say.
I'm having them off the car and take some additional pictures and see what they say.
12-03-2002, 10:06 AM
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They are fine for the street, just monitor them closely and avoid buying drilled rotors in the future.
In general I will not start the day at the track if surface cracks are visible. At Laguna Seca, which is hard on brakes, if surface cracks are visible in the morning then by the afternoon the rotors will crack big time.
In general I will not start the day at the track if surface cracks are visible. At Laguna Seca, which is hard on brakes, if surface cracks are visible in the morning then by the afternoon the rotors will crack big time.
12-03-2002, 10:51 AM
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Originally posted by wantone
Note to self: No Panther Pads...
Note to self: No Panther Pads...
12-03-2002, 11:01 AM
#20
My understanding is that today's pads don't off-gas, so slotted and drilled rotors don't really benefit anything. However, they might heat up and cool down faster, due to the reduced mass and increased cooling area.