'04Z06

So another brake question....

Been cracking my NAPA/Autozone/Etc rotors much too quickly for my liking, even with extra cooldown periods.

Considering a slight upgrade to better rotors, but am torn between the two options below (same price and appear to almost be identical). Only Difference appears to be slotted vs blank face. Not considering two-piece at this point.

Does anyone have experience with slotted vs blank rotors at the track? (not talking drilled, only slotted).


KNS Blanks:
https://knsbrakes.com/c/car-series/1...-+Single+Rotor

vs

DBA T2 Slotted
https://knsbrakes.com/c/car-series/1...-+Single+Rotor

Thanks for the help!

ErnieN85

Call KNS and talk to them for help Ken runs a C5 Z06

Spaggs

Blank ones are cheaper. In many SCCA classes they have to run blank rotors. Slotted rotators may help release heat better, but I don't if it makes that much difference given the extra expense. I have used blank ones for racing on a BMW, VW and ZO6.
Spaggs

Spaggs

Blank ones are cheaper. In many SCCA classes they have to run blank rotors. Slotted rotators may help release heat better, but I don't if it makes that much difference given the extra expense. I have used blank ones for racing on a BMW, VW and ZO6.
Spaggs

TKOGTO

Proper cooling ducts would likely help a fair amount more than different rotors. I have the Quantum kit and have run both the KNS rotors you reference. I don't see a material difference in their wear rates. Now that I think about it, I have cracked more rear rotors than fronts since the Quantum install.

'04Z06

Thank you! Exactly the information I was looking for. Brake cooling is on the upgrade list.

TrackAire

You may want to talk to Essex about cooling and cooling ducts. On my last track (1999 Mustang with the Cobra brake kit) car with solid iron rotors, I had cooling ducts and would find that cooling actually caused the rotors to crack sooner than disconnecting the ducts. Issue was the cool air was hitting the inside of the rotor face. Being a solid rotor (not a two piece) you can get a lot of thermal expansion and contraction by cooling one side more than the other. The guys at Essex turned me on to this. I had run the slotted DBA's, Brembos, etc. Ended up using non slotted Stop Tech High Carbon brake rotors and they seemed to last as long or longer than the other options I had tried and were substantially less $$.

I now have the AP racing two piece rotors on my C5Z....I don't run any duct work yet as I haven't had any braking issues. But most of my tracks are under 130 mph when coming into corners. But two piece rotors would probably handle the expansion and contraction better if the ducted air was hitting them. I know you're supposed to duct the air in towards the hub so it goes through the vanes and cools both sides of the rotor face....not always as easy to accomplish as it sounds.

Phoenix64

I cracked 6 sets of stock rotors one season. Switched to the C6 Z51 rotors in blank form.
They are 13.4inF/13inR vs 12.6/12 for the stock rotors. LOT's more mass
Still fits under the stock 17/18in wheels too.
Haven't cracked one since.

Octagon8

I assume you switched to C6 brakes rotors AND calipers or just rotors and an adapter braket to move the C5 calipers?

Bill Dearborn

Not sure what the price on the NAPA rotors is nowadays but you should consider the overall cost as well as how long other rotors may last. Running at the Glen I used to crack the NAPAs after two but sometimes three track days. It didn't matter much whether they were front or rear. When I considered all available options including pricing it was lower cost to run the NAPAs so I just carried a set of spares in the rear of the Tahoe. Of course when I started purchasing them in 2003 they were $25 each and had gone up to $50 each by the time I sold the C5Z in 2009. With a battery powered impact wrench to handle the caliper bolts I was able to change a rotor in a short period of time with the car sitting on a jack stand in the paddock. The biggest hassle was getting the tools and parts out of the Tahoe.

Bill

jpb1978

Centric makes great rotors.

TrackAire

Actually you're right, Centric is parent company of Stop Tech (IIRC) and I should have said to buy Centric High Carbon rotors in my post above.

Phoenix64

I bought the c6 caliper barkers off rock auto 200 for all 4.
I used stock c5 front calipers and the c6 rears due to the smaller piston.

Probably the biggest factor to rotor cracking is actually the TCS. If you run with it on, it kills brakes.

I can run a 1:40 at barber in the dry on trofeo R's no brake fade but in the rain on all seasons I faded the brakes running 10 seconds slower.
What was the difference?
TCS was in competition mode

https://youtu.be/ZXKOLYWBCcY

I used the centric high carbon blanks.
​​

'04Z06

Everyone, thanks for the advice! Looks like the advice is summed up as:

• (Cheapish) Blanks are a good value, just treat them as consumables. Higher quality ones may last a bit longer
• Cooling will help, but needs to be installed properly to cool both sides of the rotor
• PTM: if not disabled, can have a large impact on brake wear

I'm going to go with the KNS blanks and see what life I can get out of those. Will report back with experience this season.

mountainbiker2

Here's my StopTech rotors with only 36 autocross laps. Hawk HPS pads. Never have I had them look like this so soon.

jpb1978

Wow, just 36 autocross runs?

Rx7Rob

I have run:

el'cheapo wagners - one cracked 2nd session
lots of OEM c5 - get about four track days
lots of OEM c6 - get about four track days
KNS Blanks - currently on car

I typically change when they have lots of fine cracks, just prior to cracking through. I think the KNS may be lasting marginally longer.

I have additional cooling ducts, do a real cool-down last lap (usually pisses off everyone behind me), coast the pits before parking, and roll the car a few feet after being parked for a few min (moves that hot section of rotor between the pads). I don't think any of it really helps.

A lot probably depends on the pads. I use PFC01 up front. I don't remember their operating temp but at my last track day a corner worker (end of a straight) said my front rotors were glowing red.

I recently change the rears to ST43's and those rotors (OEM C5 rears) look great.

The HACK

Those cracks are okay. Surface cracks are common on rotors that have higher carbon content in the iron discs that goes through rapid heat/cooling cycles. High carbon count iron discs are not as pliable, but they're harder and more durable for track use (i.e. don't wear out as quickly). As long as the cracks don't reach the edge of the rotor they're perfectly fine.

I've seen club racers run with rotors that has thousands of those micro-cracks on the surface. When I ask about it, the response is usually "meh. Because race car."

R_W

I can vouch for Centric blanks off of Tire Rack. I've run them + Carbotech XP8s / XP10s for 2 seasons (in beginner group, mind you, but I am not easy on the slow-pedal as some others) and had no issues when coupled with RBF600, Speigler SSBLs, Katech front splitter brake duct inlets + LG spindle ducts. I would like to think my brake game is strong.

YYZ06

I second TrackAire. I ran the Centric high carbon rotors before upgrading the front brakes. I still use them on the rear.