Why can you fit larger tyres with a suspension lift?

[CNorman]

I am currently looking around as to how i can lift my GV. I have to say though, how does raising the suspension (not a body lift) actually allow you to fit larger tyres.

I am currently looking at fitting +30mm springs and +30mm spacers but why can i fit larger tyres, surelly when you go over a large bump the wheel and tyre still travels the full arc (-the 30mmspacer) and will still catch the wheel arch at the widest part of the wheel (the max diameter).

I have to say, i dont understand?  :-k

[glaggs]

By liftting the suspesion you increase the gap under the arches similar to doing a body lift. The adventage is simplicity and you don't raise the centre of gravity quite as much. Down side is you may still get tyre rub under the evtremes of articulation.