Came back from Summit Point with 4 cracked rotors
 

So after a gruelling day on the main track at Summit Point for a F.A.T.T. event, I find myself with 4 cracked rotors. I guess this means it's time for a brake upgrade. After doing some research ( I'm kinda on a budget after going single turbo with full bridge recently) I notice K Sport has a 14" 8 pot set up for a resonable price . Does anyone have any feedback on these?

Are the rotors microcracked (sm cracks throughout the rotor) or large cracks spread all the way out to the edge of the rotor or worse you cracked all four rotors in half :)

What's your experience level/lap time at SPR?

I'd recommend the Brembo Gran turismo kit with 99 rears.

I have cross drilled and slotted rotors. The cracks are from the holes outward to the edge. Only one crack on each rotor. This was only my 2nd track event, but I can see that this will be an on going thing.

That is your problem right there. Past threads on cross drilled rotors and why they shouldn't be used for track usage:

https://www.rx7club.com/suspension-wheels-tires-brakes-archive-112/cross-drillled-slot-brake-rotor-207758/
https://www.rx7club.com/suspension-wheels-tires-brakes-archive-112/more-drilled-vs-slotted-rotors-480082/

They are located in the Suspension Brakes Archives
https://www.rx7club.com/forumdisplay...c&daysprune=-1


What's your experience level/lap time at SPR?

Yeah, crossdrilling is mainly to reduce weight.

Weight is what you want in a rotor. Rotors don't cool in real time like an engine, they store the heat and then cool off when you're off the brakes. So, the lighter the rotor, the hotter it will get.

I know the ads say otherwise, but the ads also say a K&N will add 40% more power and sticking an adhesive disc to your fuel tank will greatly increase your fuel economy.

Crossdrilling DOES add surface area, but it adds in in useless ways. You're not going to be moving air sideways, are you? On the other hand, there are some interesting brake rotors coming out of Australia that do not have straight internal vanes but have an actual pattern, this looks like a much better way of increasing internal surface area.

The cross drilling is one problem but it's the cheap brembo rotors that are killing you. The OEM rotor is actually very good so pick some of those up from Ray at Malloy mazda or I'll sell you a used set of front and rear rotors :)

Throw some Hawk blues, DT 10 or HTC 70s front 60s rear and go from there. If you have the front R1 lip it wouldn't hurt to add the OEM front brake ducts.

Once your lap times at SPR are consistently in the 1.20s and you're melting your pads and cracking your rotors in 4 hours of track time it's time for a BBK.

Thanks for the input. I,ll go that route. I was about to dump $2000 that I had different plans for.

cracked rotors are part of roadracing, especially on tracks with long brake areas. Even the biggest and most expensive rotors will get those little cracks which eventually get bigger,.

I run a 14 inch and 1.4 wide front rotor and its all cracked to hell after a weekend, and thats with huge 5 inch ducts. And these are the pro brembo rotors used by grand am, nascar , etc. The best thing to do is get some proper ducts. I built a fiberglass mold to direct the air into the rotor with no air loss.

Another thing to remember is that you should be hard on the brakes and then completely off. New drivers tend to apply lightly, then press harder and then semi release riding them into the corner. This tends to generate more heat and gives the brakes less time to cool.

But as stated, get away from drilled rotors, add brake ducts and some good pads. If you are stil cracking rotors, time to upgrade.

These guys have you on the right track, +1 to all of the above.

Thanks guys! Very useful feedback. Can't wait for spring, now it's time to go tire shopping.