I try to get the tire heights between 25.5" and 26" on my cars. In general when the tire height gets to be around 25" or less the wheels just look small IMO, plus depending on your ride height your ground clearance can start to suffer. If you like to keep the top of the tire near the top of the wheel opening in the fender things start to get real low to the ground if your tires aren't more than 25" tall. With the 17" and larger diameter rims too the sidewalls get pretty small, so keeping the tires at least 25.5" tall keeps some sidewall on the wheels.
In the front though once you get up past ~26" you start running into clearance issues. Obviously it depends on how wide the tire is, how much backspace you can manage, ride height etc, but with decently wide tires for better handling it gets hard to pull off anything taller than 26" without cutting stuff.
