So I'm finishing my last few months in the UK and already thinking about ways to sink money into my VR4 when I move back in the fall. I've been tempted by the outlander front brake upgrade for a while but I don't want to increase forward bias since the rear brakes on these cars are already under recruited. I was digging about on RockAuto looking at caliper pistons thinking maybe I could resleave either the front or rear rotors to fix the bias and I came across these rotors from the 2013+ Outlander Sport. That model year switched to using an integrated parking brake similar to ours so the rotor doesn't have the usual drum for hub-style parking brakes.
The specs on these (and comparison to the GVR4 rotors) are:
'13+ outlander sport rear rotors: 302mm (11.88in), integrated ebrake, 10mm (0.394in) thickness, 36.22mm (1.425) height
'91 galant vr4 stock rear rotors: 265mm (10.43in), integrated ebrake, 10mm (0.394in) thickness, 49mm (1.94in) height
So, here's my thought: The rotors are bolt-on for 5-lug or a quick redrill for 4-lug (center bore is still 67.1mm so they're already hubcentric). A simple bracket made from 1/2" steel would place the GVR4 caliper almost exactly 12.8mm outboard, which is the difference between the height of the two rotors. The bracket could be designed to move the rotor radially outward by 20mm (19 for difference in radius of the two rotors + 1mm safetey), which should be enough to avoid bolt-head interference for 14mm (m12) mounting hardware. Clearance with wheels would need to be tested but in principle it's no worse and probably a lot better than other brake upgrades. Benefit would be an over-all increase in rear torque of about 15%, enough to offset forward bias from upgrading to '05 outlander fronts (which give you about 5% increase from rotor diameter and another 8% increased clamping force if you use the newer calipers, which have 43mm pistons instead of our 41.3mm). And as an added benefit, it would easily convert back to stock (winter wheels?) by just removing the bracket and reinstalling the OEM rotors, just like for the Outlander front brake upgrade.
So, I'm gonna give it a try in the fall, but I thought I'd post up the info here for posterity and see if anybody wants to buy some 2013+ Outlander Sport rotors and do a test fit(?).