The lever has a lot of travel before a shift is engaged, too, so a fair amount of sustained force was required to change each gear, which didn’t feel particularly natural. To access the fourth shift I needed to move my thumb more than was possible without rotating my wrist around the bar. It also required a lot of sustained strength.

Although the derailleur’s limit screws and b-tension were easy to set, indexing the gears was much harder than I was expecting. Cable tension was very sensitive and there was an incredibly small sweet spot where the gears shifted well.

Box Components Box One Prime 9 drivetrain performance

When lower gears were selected and chain length grew, the derailleur’s clutch tension caused the cage to be stiff pivoting forwards, so the cable-pull shifter lever was heavy throughout the lever’s throw. The cassette uses Shimano’s Hyper Glide (HG) freehub body which is different to SRAM’s XD Driver and Shimano’s Micro Spline system. The chain, made from hardened alloy steel, has chamfered shifting edges to increase shifting performance, and solid plates and pins to make it stronger. The cable release lever was also quite stiff but felt way more positive. It was only possible to shift one gear at a time, though. The cable-pull lever can shift four gears at once if pushed far enough, but accessing the last shift is virtually impossible while riding because of the amount of travel required to engage the gear.

However, it states its system isn’t compatible with 12-speed chainrings or non-narrow-wide offerings.