Hounddub Posted 3July, 2013 Report Share Posted 3July, 2013 Hey guys. Anyone here have experience in choosing rotors for a 997? I'm really not a fan of the OEM cross drilled ones for urban usage...would prefer some slotted ones if anyone can recommend. Anyone? Link to comment Share on other sites More sharing options...
JustJames Posted 3July, 2013 Report Share Posted 3July, 2013 Have you had an issue with your cross drilled rotors? Link to comment Share on other sites More sharing options...
Hounddub Posted 3July, 2013 Author Report Share Posted 3July, 2013 James, not so much problems...just loads of noise due to low speed braking. They seem to act like cheese graters. Average speed here is 25kmh per annum! Link to comment Share on other sites More sharing options...
Harvs11 Posted 3July, 2013 Report Share Posted 3July, 2013 James, not so much problems...just loads of noise due to low speed braking. They seem to act like cheese graters. Average speed here is 25kmh per annum! This sounds like a pad issue. I've used cross-drilled Zimmerman rotors on daily drive for years with out issue. Fitted with EBC track day yellow pads which are great on track and quiet and strong at low speed traffic speeds. The standard spec. Textar pads were crap and squealed all the time. Link to comment Share on other sites More sharing options...
FlatSix Posted 4July, 2013 Report Share Posted 4July, 2013 I have cross drilled rotors on both my cars and never had a problem. I think Harv is right check your pads. Link to comment Share on other sites More sharing options...
tk111 Posted 4July, 2013 Report Share Posted 4July, 2013 I was thinking of going cross drilled but have read some stories about discs cracking out from the holes? I plan on doing a few track days on them so I thought some cooling measures might suffice instead of drilled and slotted. Have you guys with drilled discs had any bad experiences with cracks or the like? Link to comment Share on other sites More sharing options...
Russ Posted 4July, 2013 Report Share Posted 4July, 2013 squealing brakes means working brakes! Link to comment Share on other sites More sharing options...
Harvs11 Posted 4July, 2013 Report Share Posted 4July, 2013 I was thinking of going cross drilled but have read some stories about discs cracking out from the holes? I plan on doing a few track days on them so I thought some cooling measures might suffice instead of drilled and slotted. Have you guys with drilled discs had any bad experiences with cracks or the like? I've done about 25,000km mostly road and a few track days on my c/d rotors and no cracks. From what I understand, the cracking only happens after extreme heat cycles. Usually after heavy use in competition. The rotors get trashed and replaced frequently by racers. On the road you will never get these temps. The holes should have a champfer around them to lessen any stress initiators to cause cracks. Both grooves and holes act by scouring the face of the pads and help to clear gases built up when braking. Link to comment Share on other sites More sharing options...
JustJames Posted 4July, 2013 Report Share Posted 4July, 2013 What Harvs said. I've always been led to believe that grooved discs are harder on pads than undrilled and ungrooved because of the scouring effect of the edge of the section of disc just after the groove. At a guess, drilled discs avoid the cheese grater effect which somebody mentioned because of the chamfering of the holes. Anyhoo, I am told that Sebro are currently re-working their designs for grooved discs, so I won't be able to get any for 997's until that is complete - this is expected to take around three months. Link to comment Share on other sites More sharing options...
Hounddub Posted 4July, 2013 Author Report Share Posted 4July, 2013 Thanks James Link to comment Share on other sites More sharing options...
Kelly Posted 4July, 2013 Report Share Posted 4July, 2013 Drilled rotors are fine for street use but a complete & expensive pain in the ass for track use. Cleaning the holes for gas venting is time consuming. Drilled rotors will start cracking after just a couple of decent track days (i.e. track days where you are carrying decent speed and threshold braking). The cracks in drilled discs are ok until they get to about 8mm from memory (I'll have to look up the actual number). The following pic is one of my discs after a couple of track days, the second pic is a Performance Friction slotted disc which was used all the way until the slots disappeared. As you can see such discs last a long time and whilst they are more expensive to buy they work out cheaper in the long run if your tracking the car regularly. Good slotted discs, properly bedded pads and good brake cooling are really help to deliver effective braking and decent life. I run PF dimpled discs on the front and drilled on the rear because the rears are less utilised and thus less subject to heat based cracking. Link to comment Share on other sites More sharing options...
Harvs11 Posted 4July, 2013 Report Share Posted 4July, 2013 WOW! I've never seen a disc worn past the grooves. You certainly got your $$ worth. Good pics. there Kelly. The cracks in the surface don't look like they go all the way to the edges so the disc is still sound albeit a bit thin. I'm guessing they held their shape and didn't warp. Link to comment Share on other sites More sharing options...
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