I want to change the clutch to my MCS 2004 but when I was buying it I read that I have to change the flywheel too or the OEM one has to be resurfaced.
Is that true, someone told me that if I take too much weight off the flywheel it can jump off by breaking the gear box.
Do I necessarily have to change the flywheel?

I am getting the Stage 2.

 

The flywheel should probably be resurfaced. Locally, that's about $30. It's beefy enough that I would not expect any problems at all.

 

The MINI flywheels cannot be resurfaced. They are dual mass flywheels, apperently that is bad for resurfacing. my mechanic said it was not possible, the exact reason was unclear; something to do with the rubber between the parts and how it gives as its tooled. i did not persue it further. but i was able to reuse my stock flywheel. he said it was in great shape, still had the groves it needs/wasn't glazed.

if you can afford it, get a lighter flywheel and an LSD. it's easy to have it all done at once. the only reason i did not was because i didnt have the money.

oh, btw, my flywheel had roughly 32k miles (about 51,500 km) on it at the time. if yours is low milage, then it will be ok (as long as it wasnt abbused)

lightened flywheels are safe to use, many on NAM have thousands of miles on theirs with no issues and only smiles.