PhonoJ

Hello,

I found a video on my previous post and now know this crank is oval on purpose and it's supposed to run that way.

Andrew R Stewart 

Previous post?

Are you referencing Shimano's Bio Pace ring design?

If so they are more "egg" shaped, not oval. Andy

PhonoJ

Yes that's the one, I had just never seen one before and was baffled by it.

Crankycrank

Explanation of Bio-Pace and other elliptical chainrings. Note that the author likes the BP chainrings so a little biased, most riders don't. Biopace Chainwheels (sheldonbrown.com)

Andrew R Stewart 

I am one who dislikes Bio Pace and other non round rings in general. Have for decades (and before Bio Pace was introduced).Some of us are rather sensitive to how we pedal, how our legs move. The Bio Pace rings changed the foot speed about their circular path. For me this different feel with the muscles and movement wasn't better. Once Bio Pace's product life was waning it became "right" to spin again and the market saw round rings in abundance.

But I do like the crank arms of Shimano's road and MtB lines during the non round era. So I have a bunch of these rings that I'll never use. They sit next to the many 144 BCD rings I have that i will also never use again Andy

Bill Kapaun

I'm just curious how a poster with one post can refer to their previous post?

ShannonM

I don't have a lot of time on Biopace rings so add salt to taste, but I could feel the differences. And I say "differences" instead of "difference" because there were more than one. In fact, Biopace rings weren't just different from round ones, they were different from themselves. Some of those differences were better, some of them were worse, and many of them were just different. It wasn't as simple as "the faster you pedal the worse they feel," which was kinda-true-but-not-always, it was more like there were some combinations of cadence, effort, foot pressure, wind, hill, phase of moon, etc, that worked really well, and I thought, "these are great!" And then something would change and I'd want to use them as throwing stars to kill skunks.

But that was 30 years ago. I'm occasionally tempted to try them again. If I do, it'll probably be the later higher-RPM ones, if I can find some in sane sizes.

--Shannon

Crankycrank

I forgot to point out that there are at least several companies that still make elliptical chainrings but they are shaped differently and generally have the hump rotated at different orientations than the Shimano BP. Still not real popular but a certain Chris Froome uses them with some mild success on the Pro Tour. (4 TDF, 1 Giro and 2 Vuelta's) Doesn't work for me though.

PhonoJ

Thanks