Rotors
Safety Car
Joined: Jan 2011
Posts: 4,959
Likes: 526
Yea....my rotors are drilled and worrying about them cracking has never even crossed my mind...esp. for street use....and I don't think i'd worry much about them cracking in moderate track use. I think theres too much forum "balderdash" going on......and please.....no pics of any cracked rotors .....
Melting Slicks
Joined: Jul 2016
Posts: 2,521
Likes: 219
From: Los Angeles CA
Yea....my rotors are drilled and worrying about them cracking has never even crossed my mind...esp. for street use....and I don't think i'd worry much about them cracking in moderate track use. I think theres too much forum "balderdash" going on......and please.....no pics of any cracked rotors .....
Drifting
Joined: Apr 2008
Posts: 1,955
Likes: 22
From: Lehigh Valley Pennsylvania
Don't listen to all these naysayers, drilled/slotted rotors look way better, and they wouldn't put them on every high performance track focused car made today it they didn't improve braking. It's not about surface area, its about gas release. Mine is a Z51 and I replaced mine with DBAs all around, they have been great.
Last edited by NormWild; Feb 1, 2019 at 04:50 PM.
Melting Slicks
Joined: Jul 2016
Posts: 2,521
Likes: 219
From: Los Angeles CA
Don't listen to all these naysayers, drilled/slotted rotors look way better, and they wouldn't put them on every high performance track focused car made today it they didn't improve braking. It's not about surface area, its about gas release. Mine is a Z51 and I replaced mine with DBAs all around, they have been great.
Safety Car
Joined: Jan 2011
Posts: 4,959
Likes: 526
Racer
Joined: May 2018
Posts: 343
Likes: 58
From: Santee Ca.
For a street car you're not gong to notice the difference. If you need more surface area you could go to bigger calipers/ more pistons/ larger brake pads/ or larger disk. There are many ways to accomplish the braking you need but for this purpose the Powerstop kit or any drilled or slotted rotor will work for a street car.
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Melting Slicks
Joined: Jul 2016
Posts: 2,521
Likes: 219
From: Los Angeles CA
Melting Slicks
Joined: Jul 2010
Posts: 3,001
Likes: 243
From: Surprise, Az
Don't listen to all these naysayers, drilled/slotted rotors look way better, and they wouldn't put them on every high performance track focused car made today it they didn't improve braking. It's not about surface area, its about gas release. Mine is a Z51 and I replaced mine with DBAs all around, they have been great.
Glad you like your DBA's, I also run their slotted version with a race track focused brake pad for track days, and a ceramic pad for street use, the compounds in the pads are compatible so they are easily interchanged without having to resurface the rotor or burnish the rotor/pad surfaces.
Race Director
Joined: Sep 2007
Posts: 16,557
Likes: 2,108
From: Peoria/Phoenix AZ
C6 of Year Finalist (performance mods) 2019
I created a drill template to drill base (JL9) rotors to look like J55 rotors. I kinda did it for looks, to fool people into thinking I still had my OEM J55 rotors, but it was really for weight savings. 
Maybe the OP would like to buy my templates and drill his existing rotors.
Maybe the OP would like to buy my templates and drill his existing rotors.
Team Owner
Joined: Apr 2008
Posts: 22,516
Likes: 1,688
From: South Carolina
edit for
I see others have supplied very good information as always..
Last edited by hawkgfr; Feb 2, 2019 at 09:40 AM.
Safety Car
Joined: Jan 2011
Posts: 4,959
Likes: 526
Why are we trying to compare F-1 brakes for this thread? F-1 brakes are a completely different animal. F-1 brakes are designed to get better the hotter they get. Actually F-1 brakes are crap until they do get hot. Not sure why people are always trying to argue the laws of physics. If you have two identical pieces of metal and you cut holes in one of them.....then bring them both up to the same high temp......the one with holes in it is gonna cool quicker. Not only is the mass reduced, but the cooling due to ventilation is increased..........
Race Director
Joined: Sep 2007
Posts: 16,557
Likes: 2,108
From: Peoria/Phoenix AZ
C6 of Year Finalist (performance mods) 2019
Why are we trying to compare F-1 brakes for this thread? F-1 brakes are a completely different animal. F-1 brakes are designed to get better the hotter they get. Actually F-1 brakes are crap until they do get hot. Not sure why people are always trying to argue the laws of physics. If you have two identical pieces of metal and you cut holes in one of them.....then bring them both up to the same high temp......the one with holes in it is gonna cool quicker. Not only is the mass reduced, but the cooling due to ventilation is increased..........
Another part of the cooling problem that includes non-drilled rotors, happens when a car with hot rotors comes to a stop and doesn't move again. The area covered by the calipers doesn't have the same rate of cooling. To avoid that problem, move the car a couple feet every few minutes.
Melting Slicks
Joined: Jul 2016
Posts: 2,521
Likes: 219
From: Los Angeles CA
Actually, a differential rate of cooling is why rotors crack. Those with holes have multiple opportunities to crack. To help against the severity and early demise, machining a full radius around the entry/exit of the drilled holes, eliminates the material where the cooling that initially occurs at the edges. Polishing the radius further reduces the chance of cracking. Looking at the pics KNSBrakes posted, you can see radially oriented cracks around holes that either have countersinks or sharp edges. The cracks are radial because the outer diameter of the rotor got hotter and cools quicker.
Another part of the cooling problem that includes non-drilled rotors, happens when a car with hot rotors comes to a stop and doesn't move again. The area covered by the calipers doesn't have the same rate of cooling. To avoid that problem, move the car a couple feet every few minutes.
Another part of the cooling problem that includes non-drilled rotors, happens when a car with hot rotors comes to a stop and doesn't move again. The area covered by the calipers doesn't have the same rate of cooling. To avoid that problem, move the car a couple feet every few minutes.
To the bolded part from Hoxxy. Road course cars get a cool down lap for this reason. Where you're supposed to make your entire lap without applying the brakes at all. The times I see the biggest problems are limited cool down then applying the parking brake. Still, you can do everything right and still break apart a drilled rotor. I have a box of them somewhere. Beyond thermal cracks I have never broken a blank rotor, and once switching to only slotted never had another thermal crack either.
Last edited by Shaolin Crane; Feb 2, 2019 at 02:17 PM.