The majority of drivetrain innovations are focused on adding cogs to cassettes and incremental improvements to shift performance, but a Canadian mechanical engineer has a radical take on derailleur design that might be a sign of things to come.

Cedric Eveleigh spent the last two years developing a new mountain bike drivetrain which he claims blends the best elements of derailleur-driven drivetrains (lightweight and efficiency) with the reliability of gearboxes. The result is Supre Drive, a drivetrain design that, for now at least, uses customized aftermarket components with oversized jockey wheels in a new orientation with a high-pivot frame Eveleigh constructed himself. The bike brand designed in conjunction with this drivetrain is known as Lal Bikes and the concept behind the design is simple: to separate shifting from chain tensioning. The benefits, according to Eveleigh, are improved shifting while protecting the derailleur and superior suspension performance, thanks to the high-pivot design.

How Supre Drive works according to its creator
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Conventional derailleurs have two functions: (1) they shift the chain across cassette sprockets, and (2) they tension the chain. These two functions are separated in the Supre Drive, with the shifting remaining with the derailleur and the chain tensioning moved to a chain tensioner at the middle of the bike.

The following image shows how the Supre Drive works. The blue line represents the chain in the lowest gear, and the red line represents the chain in the highest gear. When shifting from a high gear to a low gear, the chain tensioner arm pivots counter-clockwise around the bottom bracket axis.
Tire Bicycle Wheel Bicycles--Equipment and supplies Bicycle wheel
The derailleur has a gear shifting mechanism like that of conventional derailleurs, but there is only one pulley and no tensioner arm. The task of tensioning the chain is moved to the middle of the bike while the derailleur is focused solely on shifting. This enables the drivetrain to have more ground clearance, as shown in the following comparison with a conventional derailleur.
Bicycle Tire Bicycles--Equipment and supplies Bicycle wheel Wheel
There’s no derailleur hanger and no B-limit, making the derailleur easier to adjust.

The tensioner arm is connected by a cable to a cartridge that contains a spring and a damper. The cartridge is inside the down tube. Whereas conventional derailleurs produce increasing chain tension in the low gears, the tensioner system of the Supre Drive produces approximately constant chain tension across all gears. This is achieved by decreasing the leverage of the cable on the tensioner arm as the tensioner arm rotates back during shifts to lower gears. This decrease in leverage compensates for the increase in force from the spring. The approximately constant chain tension improves the efficiency of the Supre Drive. Additionally, the large size of the pulleys also improves the efficiency of the Supre Drive.

The damper is hydraulic and works far better than current derailleur clutches. It’s speed-sensitive, meaning that there’s a lot of force when the tensioner arm rotates fast (which occurs while riding over rough stuff) and there’s less force when the tensioner arm rotates slowly (which occurs while shifting).

The Supre Drive is compatible with off-the-shelf hubs, bottom brackets, cranks, chains, shifters, and cassettes. Two specific requirements are a 52mm chain line and a T47 bottom bracket. The latest version of the Supre Drive works with a Shimano 10-51t cassette (although the prototype bike shown here has a 10-45t cassette). Shifting performance is the same as a full Shimano drivetrain.

Coming soon to a bike near you?
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According to Eveleigh, this is a project that is moving beyond prototyping to production. He states on his website that he is collaborating with one frame company with plans to collaborate with many more.

For more information, visit Lal Bikes – introducing a new mountain bike drivetrain.