how much of a difference does .5in make on rims?

[Bimmer325]

Is there any difference in 8in wide wheels versus 8.5in wheels? My present wheels are 8.5 but I think my next may be 8 just because some companies dont offer 8.5...

how much of a difference is there, in terms of being able to push the car to a limit, etc...just wondering

[SG_M3]

an 8" wheel limits you to a 245, a 8.5" will go to a 255.