todinlaw

I Know we have beat this subject to death, could I come up with any new questions. I doubt it, but hear is the scoop. I know the standard line. rotor cracks ok until 1) the crack run to more that two holes, 2) or run to the outside of the disk.
I have rotors that the crack are getting long like a 1/2 an inch long, but they are not connecting to other holes the are just going along past the holes not connecting. I have some cracks that are close but not to the edge of the rotor. Don't have a current picture, the car is on the trailer ready to go to mid ohio in the am.

I was looking at it close and I got some cracks that are long as said above. I put the extra rotors in the truck.

should I be waiting for the holes to connect or go to the edge of the disk or does the 1/2 inch long cracks scare anyone?

Terry L

The cracks may not be alarming but I wonder how thick the rotors are at this point. If you are taking an extra set anyway it might be time for a change after day 1.

todinlaw

the wear indicator is still visible but i do have a little lip. I have been spending the evening looking at past posts. everyone is talking about cracks connecting to other holes my crack travel between the holes some crack are connecting and some I bet longer than 1/2 inch. I have had enough. I am bringing up a new set of Toyo R888s to heat cycle first run, then when I swap them out I am going to take an hr and swap rotors, then I can bed he new rotors and will have a new set of tires and rotors. Its just not worth it getting the last run our of them I may be wrong but the cracks are not only long but wide. scary.

viperbob

You have mentioned two of the conditions that mean a rotor is bad. The third is if the cracks are longer than 5mm. From the Manual "The maximum admissible perforation hole crack length is 5 mm. Further growth of perforation hole cracks or cracks at the edges of the friction disc impair braking comfort and reduce disc strength. For this reason, the components affected should be replaced as a precautionary measure".

todinlaw

Screw it, I went to the track this am. I was one of the first cars there, before the drivers meeting I had one new rotor on. It is strange, I did not have any cracks connecting to other holes but I had some cracks that joined and were about a 1/2 long or more and wide. so I swapped them. I can afford new rotors I can't afford the consequences of a failure.

In this sport peace of mind is priceless

TrackDays247.com

Amen to that. In the mean time, shoot a picture or two and let's have a look.

I can host the picture if you want me to - send to: rennstore@comcast.net

TRAKCAR

Mine were like that when I replaced them with the slotted rotors in the front, so I have the oem's as backup. On the slotted ones, I replace them when the slots are almost gone for that warm fuzzy feeling, although I don't think they are close to cracking.

The OEM rears are cheap enough to replace them when the cracks get 10mm and start connecting to each other...
I run the pads down to about 1/3 left, sometimes a little more. probably should replace at 50%.

I guess cooling down after the session is the way to keep them from cracking. FWIW:
On my Mustang with Alcon 4 piston callipers and 2 piece 1-1/4 thick rotors, I used very aggressive pads and had to run the pads metal to metal (3 sessions, black shooting out like an F1 car) cracking lots of rotors in the process. Cooling down the car for 5-10 minutes cruising around seems to pervent cracking after they have past their usual life span, I have never cracked one on track itself, always during cool down and finding out that one cracked the next time out....my 0.02c..

TrackDays247.com

I've sold several 997 GT3 Girodisc setups for front only -

The intent of the owner was to improve the wear rate of the crummy holed *front* rotors and leave the rears stock as noted above - they are cheap to replace, and wear about 4x less than the fronts.

THe Girodisc replacement *slotted* rotor rings are only about $300 each -

todinlaw

I left the rotors in a trash barrel at the track. I did have joining cracks the were more that a 1/2 inch long, scary to me. Have you posted picks of your rotor offering?

TrackDays247.com

SIZE: Front: Factory 330 mm/GiroDisc 350 mm | Rear: Factory 330 mm/GiroDisc 350 mm

WEIGHT:
Front: Factory 24 lbs./GiroDisc 22.4 lbs. - slotted
Rear: Factory 20.5 lbs./GiroDisc 18.2 lbs. - slotted

ALL hardware as weel as the disc is FULLY PLATED to resist corrosion.
100% Made in the USA.
Rotor replacement cost approx $300/ring for cost effiecent replacements -

** ANY questions, please call me at 425-765-1090 or email at rennstore@comcast.net for special Rennlist pricing. **

TurboCup87

Frank, you made a wise decision. A coupla years ago a BMW with Brembo drilled rotors had a front rotor explode on the back straight at Mid Ohio. Car was heavily damaged. If you have any concerns, you replace them. I've stayed away from drilled rotors for quite some time, but it is what the car came with. I'm trying the Deman rotors this year. The above rotors also look like a good option. Kyle

todinlaw

Agree 100%. I tried the protosport, which look just like and cost the same as Deman rotors, but I like the looks of the ones above, May have to check that out too. also nice to have a rear disk option other than stock cross drilled.