I saw this on red note and was curious about what would happen with the chain as it rotates downward on the oval shaped chainring while shifting or riding over bumpy surfaces. I noticed there was a lot of slack in the chain, particularly during downshifting. Would there be any adverse effects with the chainring shaped this way?
by freddthegr8
5 Comments
if it’s made properly, it’ll be fine
Oval shaped chainrings have been around since the 80s with Shimano Biopace and Sakae Ovaltech. Although it never took off, I don’t think chain/ring engagement was ever that big of an issue.
Close enough, welcome back Biopace. My old Biopace Trek Antelope never had issues with bumps whilst pedalling through trails/drops so I would imagine this also holds okay.
I still run biopace chainrings on two of my bikes.
Any issues you think are issues really aren’t.
Any gains are somewhat placebo in nature, but there’s a definitely unique ‘feel’ about the pedal stroke that you don’t get with regular chainrings.
Objectively they look cool and can be a bit of a talking point, as you’ve found out.
The shape of the chainring won’t noticeably affect chain security because chain tension is maintained by the sprung rear derailleur cage. As a reminder a correctly set-up 2x drivetrain can handle big-big, small-small and everything in between.
Additionally if you’ve got a 50-tooth chainring that is effectively 54t at its tallest and 46t at its shortest, it’s still wrapping around roughly half of the teeth at any point. There are only minor geometric changes to the effective chainwrap, which you might notice as a tiny oscillation in the rear derailleur pulley cage.