Test conditions ranged from icy cold and deep winter wet and mud to dry and sunny, over a mix of trail-centre style runs and more extreme off-piste runs in Scotland’s Tweed Valley – host to rounds of the Enduro World Series. Reducing tension on the adjustable clutch did lighten upshifting but increased the amount of chain slap and reduced overall chain stability, making the adjustment to a lighter setting a compromise not worth making.

The main pitfall of Box One Prime 9’s drivetrain is its dominatingly heavy shift operation caused by its stiff and slightly sticky clutch. From a pricing perspective, Box Components Box One Prime 9 drivetrain is comparable to SRAM’s GX Eagle level (once you’ve removed the cranks and chainring from the GX groupset).Team up with other players and enter the Horizon Arcade for a continuing series of fun, over-the-top challenges that keep you and your friends in the action and having fun with no menus, loading screens or lobbies. Cable tension was very sensitive and there was an incredibly small sweet spot where the gears shifted well. Create your own expressions of fun with the new EventLab gameplay toolset including custom races, challenges, stunts and new game modes.

The finish on the chain and cassette have shown little signs of wear during the test period and the teeth haven’t become hooked or the chain links stretched. Box ONE is an ever-evolving game of trivia, codes, puzzles, and discovery - only from the mind of Neil Patrick Harris. I followed the instructions to the letter to give the drivetrain the best chance possible of performing as intended. The engagement of each shift wasn’t very positive, either, which lead to occasional missed shifts when I let go of the cable-pull lever before the shifter mechanism had fully engaged.Also had to look up some of the trivia; I personally don’t enjoy puzzles where anyone couldn’t solve it based purely on reasoning as opposed to knowing a niche fact.

At the clutch’s factory setting, there was significantly more chain slap than I was expecting and when pedalling in a high gear over rough ground, the gears had a tendency to skip around the cassette. The Box One Prime 9 drivetrain might last longer than SRAM’s offerings – thanks to the chunkier chain and cassette – but I don’t think you’d be able to live with the high-resistance shifter lever once you’ve experienced a lighter system. 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.General operation was quiet, too, and shifting under power was good – as long as the shift lever was pushed far and hard enough.

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. On the plus side, shifting operation was consistent and once I’d learned to push the lever the required amount to engage the next gear, the system was easy to use. Performance-wise, GX Eagle is significantly better with crisper shifts, a lighter shifter actuation and a wider-ranging – and lighter – cassette. Alex then moved back to the UK and put his vast knowledge of mountain biking to good use by landing a job working for MBUK magazine as features editor.

The lack of on/off switch for the clutch meant that routing and joining the chain as well as inserting and removing the back wheel was much harder than derailleurs with an on/off clutch switch, such as Shimano’s 12-speed systems or SRAM’s cage lock. It has a Tri-Pack Clutch that sits behind a cap on the derailleur’s knuckle and can be adjusted using a 3mm Allen key. Installation was relatively straightforward and I was particularly thankful for the shifter’s hinged bar clamp, which meant I didn’t need to remove the grips or brake lever from the bar to install it. Although the derailleur’s limit screws and b-tension were easy to set, indexing the gears was much harder than I was expecting. I didn’t find myself stretching lower gears out with increased cadences on flatter sections or grinding up steeper hills in higher gears for longer because the gear ratios were too far apart.