450 rear calipers are also pretty expensive. Like CJC I used a rf 450 caliper on a homemade bracket.
Stock rear bracket I tried to modify to work on the rear next to 450 front bracket my creation is the bottom bracket.
Mounted
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Probable didnt make the kind of differance the fronts did but still worth the trouble. If anyone knows if a 450 rear is a direct bolt up please post pics.