Gravity bikes isn’t my scene, but I had to mention these French downhill machines from Cavalerie Bicycles utilizing the Gates carbon belt drive and a bottom bracket gearbox.
Shown is the Cavelerie Falcon, a 200mm downhill race machine utilizing the Effigear gearbox. That’s a no-dish light weight fixed gear hub on the rear wheel; the gearbox freewheels at the bottom bracket. It’s really weird to stop pedaling but you see the drive belt still moving.
Claimed benefits: weight is focused on the middle of the bike instead of to the rear for reduced unsprung weight and superior ride dynamic.
You can see this bike at the Sea Otter Expo this weekend at Laguna Seca near Monterey, California at the Philthy Bikes booth. Philthy of Philadelphia are importing these for the USA market.
You can demo any of hundreds of bikes during Sea Otter. Stop by if you have a chance.