Lots of options up front, I went with DIY GP2's, but I'm not finding upgrades for the rear. The JCW "upgrade" isn't really an upgrade since the caliper and pads are the same as stock, just a slightly bigger rotor.

 

The only real “upgrade” is the Wilwood kit. I say “upgrade” because you have to make some compromises when installing it.

Some other food for thought… the GP2 uses the same rear brake setup as the ‘regular’ JCW…

Is there a reason you want a bigger rear brake setup? What do you find deficient about the rear brakes? Is it just for looks, or are you actually seeking a performance upgrade? Since the R56 carries so much of its weight up front, the front brakes provide the majority of the stopping power. Pad selection will be more important to actual brake performance than rotor size.

 

I have not had it on track yet, but seems like a BIG discrepancy between GP2's up front and basically stock (JCW's) in the back. Although, as you said, it's the same setup the GP2 came with, so if Mini thought they needed to be bigger then they'd be bigger. I'm running EBC Yellow on the street, Hawk DTC-60 on the track (COTA).

 

Yup, Mini basically has only two different sized rear brakes for the R56. The smallest are the Cooper / Cooper S at 259mm, and the JCW/GP2 at 280mm.

For what it's worth, I run the JCW rears and BMW / GP2 fronts on my Clubman, and I feel the brakes are MORE than adequate for street use. And I'm only running inexpensive RockAuto street pads. If I REALLY stomp on it, I can get the ABS to activate, which means I'm tire limited for braking power. With a slightly better tire, I'd bet my braking distance could be reduced dramatically. I imagine you're doing way better than me with track pads and tires. Front GP2 rotors should give you plenty of heat capacity, too.

 

how does it feel to be punting the R56 around such a high speed power circuit ?

the willwood kit for the R53/56 does have a larger disc at the rear, but its still a small caliper. you would do it more for the lower unsprung than the power increase. what im meaning here is that its really only the front you need to think about if your wanting more stopping power.

 

It's a hoot!!! And it's only about 30 minutes away from home, I can't wait to get back out there with the brake upgrade in October! The last trip was fun, but I had to brake WAY early.

Yeah, I looked at the Wilwoods and basically said, "Yeah, not much different than what I have now." I just kinda wonder if I'm going to need to worry about the rear wanting to swap ends with so much front bias. But if Mini thought the GP2 needed different rear brakes then it would have different rear brakes,

 

Very good points. I tend to claim nobody needs bigger rotors or even bigger calipers on rear whether on street or track. On track you want to brake ~1 g or even harder (depending on tires and tarmac/circuit), resulting in less than 10 percent with your rear brakes. Former European Mini Challenge used to run 6-pot AP calipers (330 mm?) on front and stock rear calipers including stock 280 mm rotors. Dedicated racing pads available (Pagid RSL29, Ferodo DS1.1 etc.).
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We just loaded up tarox and they have some options now.

https://www.ecstuning.com/b-tarox-parts/v-mini/

 

I keep seeing this thread from the main page, so I'll bite.

Rears are mostly weird because they have the manual integrated parking brake, so you're very limited in aftermarket options.

R56 Rear calipers are 36mm with 259mm (S) or 280mm (JCW & GP2) rotors.
R60/R61 S/JCW Rear calipers are 38mm with 280mm (S) or 296 (JCW) rotors.

So ~10% bump in piston area, plus some more if you run the 296. Pretty big jump, and probably not worth it.

Probably not a direct fit, but there's only one way to find out. Someone pull the trigger or bribe an R6x buddy lol.

Also, FWIW, the R60/61 Rotors are 79mm CB, which would need a massive spacer. F6x versions are supposedly 67mm and very similar otherwise.
Basically redrill to 4X100 and buy a 64.1 - 67mm hubcentric ring.
I'd solve the caliper first, then tackle the rotor problem.