[Hib Halverson]

If it where me, unless I needed more clearance for bigger brakes, I'd never put 19s or 20s on a C4.

The reason is the tires have much shorter sidewalls. Such low profile tires noticeably increase harshness and C4s are bad enough already in that respect.

There is also the height issue but that can be fixed with 3.73 or 4.10 gears.