Innovation of the Year Winner
2021's Innovation of the Year nominees
include RockShox' suspension-controlling Flight Attendant, the Digit Datum with its novel suspension design, the latest long-range ebikes and a product that promises to minimise the disadvantages of air suspension. But this year's winner is the brainchild of a young Canadian engineer that could save a lot of mechanical maladies.
The derailleur is possibly the best and worst idea in mountain biking. We all know that derailleurs suck. They're expensive, fragile and finicky, yet highly exposed to impacts from stumps and stones. But in a way, they're a really elegant solution.
The derailleur not only selects the sprocket, but its cage also takes up the spare chain when you shift to a smaller sprocket. This tensioning function is a gift to full-suspension bikes as it can also spool out more chain when the suspension compresses and the hub moves further away from the bottom bracket. And because you need a chain anyway to transmit the drive from the crank to the wheel, it's more efficient to use the chain as part of the shifting mechanism, rather than having a separate gearbox plus a chain connecting it to the wheel and a tensioner pulley to allow for suspension movement
For this reason, plus the need for inter-meshing spur gears in gearboxes, derailleurs are the lightest and most efficient geared drivetrains. Gearboxes may be more reliable, but they add too much weight, cost and drag to go mainstream.
Cedric Eveleigh wasn't satisfied with conventional derailleurs or gearboxes. Inspired by CeramicSpeed's Driven
drivetrain, he started brainstorming ideas to solve what he calls "the most glaring issue with mountain bikes" - derailleurs. On a ride in 2019, he thought of this concept and started building prototypes right away.
The basic idea is to separate the two functions of the derailleur (shifting the chain across the cassette and tensioning the chain). The lateral shifting mechanism with its guide pulley remains by the cassette but is tucked out the way. Meanwhile, the tensioner pulley, which normally hangs down amongst the rocks and roots, is moved to the bottom bracket. This massively improves clearance and reduces the risk of ride-ending derailleur impacts.
It also moves some weight from the rear wheel, where it harms suspension performance, to the mainframe, where it doesn't. Plus, because the two pulleys are larger than a conventional derailleur, and because there's no need for an additional guide pulley behind the chainring, Cedric claims drag is reduced compared to a conventional idler bike with a derailleur. As if that weren't enough, the tensioner is said to provide more consistent chain tension and better damping than conventional clutch derailleurs, reducing chain slap and noise.
Because of the position of the tensioner, the design only works with idler pulley bikes, and only ones with the idler positioned forwards out of the way. Perhaps this explains why nobody has thought of it until now; only in the last couple of years have idler bikes become more mainstream. The plan is for Lal Bikes to build the drivetrain components, and license the system to bike brands to design their bikes around it.
It won't be available until 2023, but we've ridden a prototype around the car park and the shifting worked flawlessly. Apparently, several bike brands have already shown keen interest in the idea, and given the original article
already has almost 200,000 page views, it seems the concept is interesting to many of you as well.
Whether the Supre Drive is viable as a production product remains to be seen, and we're not suggesting it's going to take over from conventional derailleurs. But this is the first radically new drivetrain concept we've seen in a long time that doesn't have readily apparent weight, efficiency, or shifting drawbacks.