When a new standard arrives, there’s usually a backlash lasting months or even years. But the 55mm chainline got in under the radar. Though not a “standard” in the traditional sense, 55 does impact cranks, chainrings, cassettes, and frames. So, it counts. The goal is to offer more room for wider tires, sturdier frames, and bigger chainrings by bumping that (single) chainring outboard to sit 55mm from the bike’s center line. That’s 3mm further than the 52mm chainline most brands have been using since Boost 148 dropout spacing took hold. This issue may seem pretty inside-baseball, but when we learned SRAM Transmission was designed specifically around a 55mm chainline, Travis Engel figured it was a good time to take a closer look.
