OChain claims their Active Spider provides at least some of the benefits of removing the chain altogether. While riding bike park laps without a chain is possible (despite still requiring some 'skating') it's out of the question for trail riding. And you wouldn't dare race a World Cup without a chain; unless it breaks out of the start hut, as it did for Aaron Gwin. Many World Cup Downhill racers have used the OChain device now, including the current World Champion, Reece Wilson, who had it on when he won last year in Leogang. Looking at the coverage from the weekend in Leogang, OChain’s use at the World Cup level appears to be growing. Troy Brosnan is a notable racer using the spider, racing it to another victory at the first World Cup DH of 2021.
A couple of the scenarios that can affect the chain. Notable are the bounce tests where the OChain Active Spider can isolate some of the impact from the chain on the pedals and cranks.
The OChain spider allows the chain to rotate backwards a small amount, effectively isolating the chain’s movement from the feet as the rear wheel is compressed and extended repeatedly. Many dual-suspension mountain bikes have a rearward portion to the wheel's axle path, usually in the early part of wheel travel, which lengthens the chain in response to an impact. Our derailleurs allow for chain growth, which explains why single speed setups won't work without a tensioner or derailleur on dual-suspension bikes, but there are also forces pulling at the top of the chainring that the derailleur doesn’t counteract. This only partly explains why the bike feels different when the chain is removed because there's something else going on.
The chain bouncing up and down as the wheel encounters impacts also changes how the bike feels. How greatly this affects the bike will depend on the suspension kinematics to a degree but also the length of the chain, the gap between chain and stay, and also the terrain. To counteract the chain's effects on the chainring/cranks and suspension, OChain's Active Spider rotates backwards a set amount. Provided elastomers of three sizes allow either 4, 6, or 9 degrees of backward rotation, with an option to purchase a 12-degree setup as well.* With many different suspension designs and riding styles on the trails, OChain provides the four sizes to allow users to customize the feel.
*OChain originally released the Active Spider with 6, 9, and 12-degree setups but has since updated it to the settings above.
