The rear derailleur is one of the most fragile components on a mountain bike, subject to getting bent or jammed up with trail debris. That's where the Supre Drive drivetrain comes in, as it moves the derailleur up and divides its functions between two locations.
The prototype system was invented by Canadian mechanical engineer Cedric Eveleigh, who is commercializing the technology via his Lal Bikes company. It addresses one of the key problems with existing derailleurs – the fact that they hang down close to the ground, supported only at the top.
In Supre Drive, the single-pulley derailleur body is mounted on a system-specific rear swingarm (it can also be used on hardtail bikes), where it sits to one side of the cassette – not beneath it. There, it performs its usual task of moving the chain back and forth between the sprockets. It's rigidly mounted at two points, however, plus it's protected against side impacts by the overlying swingarm assembly. This means the bike can be laid down on its drive side without any risk of bending the derailleur.
Of course, along with moving the chain sideways, conventional rear derailleurs also keep it tensioned. In the case of Supre Drive, that function is performed by a separate hydraulic-damped tensioner arm which pivots around the bottom bracket axis. This arrangement allows a consistent amount of tension to be applied throughout the gear range – with regular derailleurs, the tension increases as the gears get lower.
And as a side benefit, because the chain is held relatively high, there's reportedly no chance of it slapping against the ground when the rear suspension compresses during hard landings. When removing or reinstalling the rear wheel, the tensioner can be locked to provide the required chain slack.
Weight-wise, the system is claimed to be 100 to 200 grams heavier than a regular Shimano XT drivetrain on a high-pivot mountain bike, although it actually has about 130 grams less unsprung weight – this is due to the fact that the derailleur is shorter, plus less of the chain is located near the cassette. The total length of chain required is about the same as that presently used on high-pivot bikes.
Importantly, Eveleigh adds that Supre Drive is much lighter than internal gearbox-based drivetrains, which are an existing alternative to conventional derailleurs. He claims that it also produces less drag as the rider is pedaling, making it more efficient at converting their muscle power into forward motion.
The system is compatible with third-party hubs, bottom brackets, cranks, chains, shifters and cassettes, although it does obviously have to be built into the bike from the start – it can't be retrofitted onto existing bikes. To that end, Eveleigh plans on selling the components to bicycle manufacturers, which will in turn incorporate them into their bikes. He tells us that he's presently collaborating with one frame company, but is open to enquiries from others.
Supre Drive has already been built into two test bikes, one of which Cedric puts through its paces in the video below.
Source: Lal Bikes
