[rhinoceraptor]

I'm sure this is a neat system, but it's worth noting that bicycles are already very efficient, the difference between their claimed efficiency and a properly set up traditional drivetrain is maybe one or two percent.

And any weight savings are probably useless due to the minimum weight required for racing. Pro bikes are basically at the point where they're having to add weight just to pass inspection. This system might have a bit less rotational mass in the "cassette" than a traditional cassette which would help.

[folkrav]

I've ridded a half-decent street bike a summer or two. This thing was light enough that as a tall slightly chubby man I felt uneasy just getting on it, I kept thinking "this thing will crumble from my weight". I knew it was stronger than that, but my brain kept telling me something wasn't right.

And it was a pretty mid-range bike.

[LeifCarrotson]

As a tall, lean cyclist I'm always a bit surprised by both the extremes that people go to in weight reduction and by the palpable speed difference that you feel when riding a light bike.

When I ride a 1980s steel road bike, we (bike+rider) weigh about 75 kg. On a modern carbon-fiber bike, we weigh about 71 kg. That's a 5% difference, but the latter feels like it has rocket boosters when I get out of the saddle to sprint up a climb, while the former feels like I'm carrying an anchor the whole ride. Borrowing a friend's hill climb fixie machine well under the UCI weight limit gives even more of an exhilaration of speed. But conversely, adding 30lbs of bags to go touring doesn't feel that much more difficult once you're up to speed.

[davidbanham]

I wouldn't be surprised if most of that difference in feel could be explained by frame rigidity rather than weight. I love my steel frame but I know it's not super efficient.

[rhinoceraptor]

IMO it’s probably that wheels are a lot lighter now. Rotational mass is a killer.

[pmontra]

I've got two different sets of wheels for the same gravel bike. Its standard 42 mm wheels for gravel and 28 mm slick wheels I assembled for road. Same brake rotors and same gears on the back. The set of road wheels is about 1.5 kg lighter (3 pounds). The bicycle seems to fly with them. Rotational mass is really important and also slick vs threaded.

[davidbanham]

True, good point.

[mrob]

See also: people overinflating their tires because it feels "fast", even when measured performance on real-world roads is actually worse.

[berbec]

I think you could get more gains by using the restroom before a race.