Lal Bikes' Did Efficiency Tests on the Supre Drivetrain - An Update

For those who don't remember, Lal Bikes' Supre drivetrain won Pinkbike's 2021 Innovation Of The Year award. It's the brainchild of Canadian engineer, Cedric Eveleigh, and the idea is to improve the reliability and efficiency of derailleur drivetrains for high-pivot bikes, by moving the chain tensioner pulley to the bottom bracket, out of harm's way. You can read about the details here or even more here, or find out why we thought it was the best innovation of 2021 here.



Production bikes featuring the Supre drivetrain aren't due until 2023, but Cedric has been doing some interesting tests and we thought it was time for a little update.

One of Cedric's aims is to improve upon the efficiency of conventional drivetrains on high pivot bikes. Because the chain passes over the idler wheel while under a lot of tension, high pivot bikes are less efficient than conventional bikes, and so a little slower uphill. In a recent test, I found a high pivot bike with an idler was about 2% less efficient than a comparable "low pivot" bike.


But Cedric claims to be able to narrow this efficiency gap with his drivetrain. That's partly because the gear-selecting and tensioning pulleys are larger than those in a conventional derailleur, and the larger pulleys mean the chain pins don't have to articulate through as much of an angle when they wind their way through them. For the same reason, the 22-tooth idler pulley is larger than most high pivot bikes, plus it's further away from the cassette, which minimises cross-chain angles at either end of the gearing range. Finally, the frame-mounted tensioner uses a hydraulic damper instead of a friction clutch like you'd find in most derailleurs; this allows the chain tension to be reduced, without causing excessive chain slap, and lower chain tension further reduces friction.


To prove the efficiency of his drivetrain, Cedric tested it on a purpose-built test rig in Germany, alongside a conventional derailleur drivetrain without an idler. He also tested a high pivot drivetrain with a conventional derailleur, but the same large idler pulley that the Supre system uses, placed at the same position relative to the cassette (you can think of this as a best-case scenario for a drivetrain with an idler and a normal derailleur). According to Lal Bikes, the Supre drivetrain was on average about 0.9% less efficient than a conventional low-pivot derailleur drivetrain, but slightly more efficient than the "best-case" high-pivot drivetrain with a conventional derailleur.


The advantage compared to the "best case" high pivot drivetrain may be tiny, but given most high pivots use 16-18 tooth pulleys (not 22-tooth), have the idler closer to the cassette, and in many cases also require a lower roller guide, the real world efficiency of many high pivot drivetrains could be considerably lower. If the efficiency test I did is anything to go by, a conventional high pivot with a 16-tooth idler and a lower guide is around 2% less efficient than a conventional low pivot drivetrain. Whereas, according to Lal bikes' numbers, the Supre drivetrain more than halves this disadvantage to less than 1%.

As always, take any manufacturer's claims with a pinch of salt (even if they have a nice graph), but it seems reasonable to assume the Supre drivetrain will be more efficient than existing high-pivot systems. Given its main selling point is the promise of better reliability, that's a nice bonus.