So you want better brakes on your R100GS??? Why not try something already available from BMW???? Like one of these calipers. The mounting tab spacing of the R100GS caliper is the same as the left 4 pot Brembo from a R1100xx, K1100xx, R1200C or an early R1150GS (up to 11/2001). I can't take credit for finding out that this works as there are a few references posted here on ADV Rider about the conversion. The only modification needed is to remove 0.158" off the caliper mounting tabs. This keeps the rotor centered to the caliper. I double checked the measurement and came within a few thousandths of and inch good enough. One thing that concerned me, was milling that much material would make the tabs too thin. The stock 2 pot Brembo is 0.489 inch thick The left 4 pot Brembo before milling tabs ( 0.609") Area of material removed (0.158") Thickness of tab after milling (0.451") With 0.158" milled off the mounting tabs, the 4 pot Brembo is 0.038" thinner than the stock 2 pot Brembo.