wheel sizes(front and rear different)

[barryogen]

Is there some thick and fast rule to wheel sizes?

The top end "hyper cars" seem to always have differences of an inch or two on the rims front and rear... any real reason for this?

Googling doesn't seem to be bringing me any luck, and the only reason I can think of is that maybe they want to have a bit more sidewall on the front.

*edit* to clarify
Say an imaginary lambo comes with 20" wheels on the back, and 19s on the front, but with the tyres on the front having more sidewall to keep the same circumference as the one on the back... I would have thought you would just put 20s on it all round, but they don't, so why is that?

[Mr.Phreak]

The top end "hyper cars" seem to always have differences of an inch or two on the rims front and rear... any real reason for this?

It's hard to fit wide wheels up front and still be able to have them turn

Plus aquaplaning steering wheels is awesome

[barryogen]

It's hard to fit wide wheels up front and still be able to have them turn

Plus aquaplaning steering wheels is awesome

that would explain why you don't have the same width, but not a different size rim, maybe I should have been clearer with my question.

I was meaning that an imaginary lambo comes with 20" wheels on the back, and 19s on the front, but with the tyres on the front having more sidewall to keep the same circumference as the one on the back... I would have thought you would just put 20s on it all round, but with different widths to keep the ability to turn as you mentioned above.

[Bling]

usually the bigger a rim the relatively wider it is, I think thats what Mr.Phreak was getting at. A 20" rim may be wider than a 19". but custom wheels will rule that out, so I have no answer for your hypothetical question

[Mr.Phreak]

Only thing I can think of is aesthetics, sorry, thought you were talking width not diameter

[Jdawg]

Tyre contact patch is longer, therefore bigger with a bigger diameter giving more grip for acceleration, most "Hyper" cars are rear wheel drive.
I would think for the front a shorter and wider footprint is probably desired

[Dell'Orto]

Pretty sure its just an aesthetics things, Check out hotrods from back in the day, usually larger rear rims. Kinda takes a cue from dragracing.