wider rear axle,track width,suspension questions

[NoHachi]

Never widened an AE86, so I have no practical experience. But for circuit work almost all fast AE86s go towards a wider square setup (wheel base = wheel length). Rally setup is different I think, you could take a long hard look at all the ridiculously fast AE86s in Scandinavia.

Just remember that a much wider track will require upgrades in spring rate and shock valving to end up at the same wheelrate as the original setup.