hey i have a 6n and was wondering how low can it go before i have to roll the arches? the wheels are 7j i think! thanks! :P

Seems like an obvious answer, but when the wheels start to touch the arches?

If you want an answer as in a measurement then you're best going out and measuring on your own car. As it will depend on your tyre size and offset when the tyres will contact the arch if at all.

A friend used to run a low 6n with 14 x 7 or 14 x 8 I cant remember but he had more issues with the pan hitting the road than the tyres and arches to be honest.