Wondering if they will fit a 2013 JCW without rubbing.

A GP is a JCW.

After doing some further research, I've determined that they won't rub even though the tires are a different size.

They run the same size tire I use 215/45/17. Many of us run them and wider without rubbing as long as you use the right offset and don't go to low.

I've put some GP wheels on my Clubman - no issues with 215/45/17 tires. The wider GP wheels do stick out just a bit more compared to the stock JCW 17" wheels.

This is a terribly misleading and incorrect statement. The GP calipers are MASSIVE. The dealer tried my JCW snow wheels on my GP yesterday. They don't even come close to fitting...

There is nothing misleading about it. The fact is a GP is a JCW and I never said they would fit or not fit. Just the fact that it is a JCW.

Then what was the purpose of your response?

Because you asked if GP wheels will fir a JCW. So I was letting you know that a GP is a JCW. Now as far as wheels, again YES GP wheels will fit a JCW because JCW calipers are not as large as a GP. In reverse they won't fit again because the calipers on the GP are larger then the JCW.

This is reverse of the question answered. So NO your JCW stock wheels wont clear GP calipers like he said. But JCW calipers are not as large as GP calipers so in reverse there are no issues. I hope this clears it up.