Help with wheel spacers

Hi, some help please..

my Coop ( 16vt ) has a wheel set up of 225/45/17 but the rear wheeel scrathes the wheel arch. The spacers are 20mm, thinking if I cut them 10mm will that clear the tyre?? And will it be enough for the brembos on front?
What usually is the correct set up for this?

Best regards

Depends on the spoke design and offset of your wheels. I think standard on the 16vt is 35 or 40mm. Someone wiser will know on here shortly......
Use this to help when you know the offset.
http://www.willtheyfit.com/

You can then use the correct spacer. I believe I have a 10mm spacer on mine to fit the 17in wheels I have.

I guess the spokes are no problem, and the offset of the wheel is 35 ... i'll give it a try... or should i change to 215/40/17?