Originally Posted by onespeedbiker

The distance between the bosses can very and result in issues with the brakes. The older cantis used coil springs which had a long linear tension, however the new cantis like the BR-R550 use a straight tension spring, which is cheaper, but ramps up very fast so they don't start to tension until very close to the rim surface. Further, Shimano Cantis are designed around 80mm wide bosses (c to c). However frame makers use various widths depending on the width of the stays and fork blades. Attached is a graph that shows how to set up the brake shoe spacers to accommodate bosses of different widths..good luck.

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