Whats everyone's opinion on this? I don't plan on tracking this car much but I'm sure it will go 2 or 3 times since my buddy has been waiting for me to get into a car for years. Not sure I really need this upgrade. Would it be a safe bet to not get it and then just upgrade later if I decide I need the upgrade. Are the rotors bigger or just drilled and slotted?

 

The best advice I can give if you want to track your car, even occasionally, is to work on your skills first. The MINI is a very capable car on the track, even when 100% stock.

As long as you have changed the brake fluid with in the last 6 months, and have good pad remaining, you should be fine. A set of EBC brake pads is also an option, and can improve your braking.

If/when you are ready to invest in mods for the track, there are many areas to consider. Suspension, brakes, safety, performance. Larger brakes can help, and there are many options such as JCW and aftermarket Big Brake Kits (BBK) available.

On the plus side for JCW is that they do work, and have warranty.

 

Front and rear rotors are both bigger, front ones more meaningfully so. Make sure you know only some 17" factory wheels work with them. Rears are never drilled or slotted. Fronts are not on a factory car, but may be in the kit. Apparently not in Europe though, at least not on the ones you find on Ebay. Front drilled and slotted rotors are also available as a piece part from the dealer, but the patterns only run in one direction regardless of side; the norm are directional rotors for each side, but not from Mini.

Front is where the bigger differences carry over to the calipers--large four piston calipers from Brembo. Aluminum rather than steel/cast. Having weighed the parts, while the rotors are bigger, the shift to an aluminum caliper leaves the net front weight of all the brake hardware about the same as the stock S set up. In the rear, it appears to be the identical caliper to the S, just with a good red paint job. The mounting bracket is different by part number, and appears to me to be the difference and how they in turn space it to then use marginally bigger rotors. Rear pads are also identical between JCW and S, while in front they are clearly different.

A few, but not a lot, of aftermarket choices are available for the rotors and front pads. Given rear pads are interchangeable to S, already more choices there. FWIW, I found the front calipers have become more available in the UK via ebay. I bought a set of those and sourced the rotors and pads of my choice here. So far have made no changes to the rear. Brakes have nice feel given the 4 piston set up. Switched to Carbotech Bobcat front pads (nice feel, way less dust), with some teething difficulties where they don't seem to have their act together on the backing shims. The big delta would be on aggressive use with the greater overall rotor mass, the aluminum calipers and quality of the set up would come into play. For regular street, either can of course stop the car easily and kick in ABS. Remember stock gen 2 S is the same as full JCW for gen 1.

Your most cost effective upgrade would be to a somewhat better pad with the stock set up for general performance and perhaps less dust, accompanied by fluid changes at least at the regular service intervals. You can source a variety of rotors in the stock size when the time comes, but realistically the patterns (beyond slotted) are predominantly for show not for go (stop).