S13 Front brakes in AE86 rear

[Bean]

I see - I think bigger discs would already help. You can always trial fit the fronts from the S13 to the rear and see what needs to be done.
I did a lot of work on both cars but haven't seen an S13 in years now so not sure on the differences. I'll see what I can dig up (to be edited soon).

S13 front disc (280mm)

S13 front disc (257mm)

AE86 rear disc (231.5mm)


for the sake of a complete overview
AE86 front disc (234mm)

S13 rear discs (266mm)


you definitely need to change the caliper mount - if everything will clear I can't tell. As a pointer though the S14 has only 258mm dia solid rear discs

I assume you have some very sticky wide tires on the rear as I have not much problem to lock my rears with the stock setup, if I yank hard enough.