Is it ok to use 2-1/2" whites up front and 4" on the back or will it look wrong? (1941 Ford pickup) ADDED - big and little tires (165x15 front / 255x70-15 rear)
With 'big & littles' it usually looks best if the taller tire has a wider white wall, my thoughts. For my Model A, I am doing BFGs 5.90s and 8.20s, 2-1/2" wide WW in front, and 4" wide WW on back.
If you are running a taller tire on back you almost have to put a smaller ww on the front or it will look odd. You generally want about and equal amount of black showing on both sizes or the tires will look like they are all ww and no black. Don
I think most cars look good with the smaller whitewall up front and the larger in the rear. I do think however, some cars can use the opposite logic. With fender skirts you can have a slightly smaller whitewall in the rear to level the car (think 1950 mercury or a stationwagon) and the look of the car could be awesome.
There are no rules for what you like, your ride, your rules! Do what you think looks cool, you'll never be happy pleasing others......