I run an '07 MCS R56 with all of the JCW bits including the drilled and slotted rotors. I track the car and just got back from two days at Watkins Glen. When replacing my Carbotech XP10 pads tonight, I noticed radial cracking on almost all of the drilled ports on the rotors. The slots were fine.

Not too good, eh?

 

This is so common in drilled rotors that it is almost natural. Time to evaluate your braking style, and maybe even a bit of equipment. If most of your tracks are heavy braking tracks, you might think about floating rotors and just maybe, bigger calipers. But first, think about braking style. On a scale of 0 to 10.5, where 10.5 is full on lockup and 0 is no brake, when hitting your braking spot, quickly brake to 6 to settle/squat the car, then hard down to 10, 10, 10, 10, 9, 8, 7, 6 on down to off the brakes and turn.
The plan is to get about 80% of your braking done in the 1st 20% of the brake zone. This will allow you to shorten your braking time, which won't put so much heat deep into the rotor. Surface heating will cool more quickly, and your brakes will last longer, and your lap times will fall.

Yeah, yeah - I know. ABS. Whatever.

Regardless, drilled rotors crack. Fact of life. Slotted work fine. So do non-modified rotors.

 

holly cow!
Always heard this happens to drilled rotors, just never seen any pics.

 

You put 1st Generation JCW brakes on an R56? I was told that the standard brakes on the R56 MCS were the same size as the 1st Generation JCW. So, the main difference between standard 2007 MCS brakes and those JCWs are the holes and slots. Am I wrong in thinking you'd be better off with standard MCS rotors?

 

What I meant was that I have the 2007 R56 factory brakes with the JCW slotted/drilled rotors that were offered for that year ... what I thought was being called Gen 1 for the brakes to differentiate between the 2007 R56 and subsequent years. I did no retrofitting of R53 JCW brakes. Does that make any sense? Thanks!

 

Good advice, for sure. I have been working on squeezing the brakes on versus coming down fairly hard on them, but I'm sure that somewhere in the learning curve, especially early last year, I was tough on these rotors.

So, time to replace, right?

 

Those don't appear to be too bad. When Bob Bondurant first moved to Phoenix, he used modified Mustangs in his school. Part of the course was practicing heel and toe braking/downshifting on the drag strip. The deal was to drive down the dragstrip, get into third, H&T to second, accel to third and repeat. When you got to one end of the strip, turn around and do it some more. Well, after a half mile of 3 to 2 and 2 to 3, we started putting the hammer down and the downshifts were from 5 to 4 to 3 to 2, all the while on the brake. Pretty soon I started getting the warped rotor shudder. Pretty soon after that, I got the VIOLENT warped rotor shudder. So I stopped next to an instructor to discuss, and while talking to him, CLANK! a chunk of rotor popped off. Definitely time to replace THOSE rotors.

I don't want to sound casual about your brakes. I know guys who would do a couple more track days on those. I think you would be OK on the street for a while, but I wouldn't use them again at track speeds. Consider the cost of rotors vs wheel/suspension damage and maybe worse.

Track rule for everybody. Don't use "good enough" parts. The cost of a failure can be quite large. Just how lucky do YOU feel today. Replace worn or suspect parts. ALWAYS.

 

That's the kind of advice that I was seeking. Time to go combing through the threads to see what's out there to use with my current calipers ... don't want a full brake upgrade yet. Thanks!

 

Dealer has oem air brake ducts available for R56 now, if you plan on keeping brakes.

+1 on getting non-modified rotors (ie: standard JCW/R56 rotors)

 

I have a set of JCW/R56 rotors in the garage. 6k miles on them.....$70.

 

I'd be more concerned about the use. You have the wrong pads and rotors for whatever you're doing. The cracking is from thermal expansion problems and common to all drilled rotors. The other issue however is the excessive pad smear shown on the rotor. Wrong pad, wrong rotor for your driving style.



That's not a crack...that's just a fracture. This is a crack:

 

Hi Todd,
I was thinking about emailing you... Will send you a PM tonight. Thanks!

 

Before anyone gets disjointed about my "wrong pad" comment I want to make it clear my personal opinion is that the pad issue is based on being combined with the rotor and use- not that the XP10s are a poor pad.

Placing this pad into service for this type of use and at this level is only as good as the disc it's working upon. The rotor above shows the pad reaching it's thermal limit and breaking down, I suspect both from the demands and the temperature imbalance created by the holes. In looking over Carbotech's pad listing I'd say this would have been more stable using the XP12s where from the data the pad is geared toward more high temps.

The problem here is that the car remains "rotor challenged" using the 10s on a larger rotor would have kept the temps down some and things may well have been dandy. But continually pounding on a smaller rotor you can only ask so much of the pad as the rotor cannot do its job of cycling the heat. Of course the track itself can effect this too.

I call it all about duty cycle. Increasing the efficiency lowers the duty cycle. There is simply no substitute for more rotor mass.

 

Watkins Glen especially the short course is really hard on brakes and tires. So far, I have done 7 track days at Watkins with the same Carbotech XP10s and stock rotor w/o any problems. As Pat had mentioned, be careful with threshold and trail braking especially at turn 1 and the bus stop. I learned a long time ago that you have to be gentle with the car.

I would replace the rotors and perhaps do with ones that are not drilled. If you go with XP12 pads, you may need to replace them before street use.