I know what you mean. After about 60 years of doing a left-side leg press every time I accelerate from a stop on my track and fixed-gear bikes, as well as struggling up inappropriately steep climbs in a 71-inch gear, I'm left with a pretty bad left knee. Not yet painful, or not all the time, but it never lets me forget.

I'm thinking of getting a 110-BCD Hollowtech II crankset for my current fixed-gear bike and installing one of the 42-tooth Biotech rings I still have stored somewhere.

I have a couple bikes with Ovaltech and a couple with Biopace. I can't feel any difference from my bikes with round chain rings. One exception was a bike that I built up from parts out of the infamous Box O' Crap. I had a single 39 tooth ring Biopace that I put on a crank with a 52 tooth round outer ring. I don't know if it was one of the older versions. I could definitely feel the pulsing as I pedaled, to the point that it was annoying. I took the Biopace ring off and replaced it with a round ring.

I'm assuming you have the "paratrooper knees" as well...

I'd hear people complain about their knees hurting- I was just like "duh... knees hurt... that's what they do" because for my entire adult life they hurt. Around 10 years ago they started grinding- I don't know if they hurt much of any more, but the grinding made me feel like my bones were directly rubbing on each other- and it's a scary feeling. That's what you get for carrying your body weight on your back.

I was 129 when I ETSd. Here's a pic of me getting jumpmastered with a 153 pound ruck. I could only stand upright for a few seconds at a time and I pretty much had to be shoved out the door.

Yes. Experienced riders like you generally maintain a cadence well above the cadences of around 50 to 70 rpm that casual riders usually use and that Biopace was designed for.

TEN MONTHS without a Biopace discussion? Gotta fix that!
Had to dig through my box of chain rings yesterday to find a SS ring.
So many more Biopace than round rings! I think a bunch were take-offs from Colorado Cycle when they were new.
They hurt my knees, and looked foolish.


Worst was this one, came on my Cannondale tourer. Uphill it felt klump-klump-klump JUST like a flat tire.


They did have a second generation that was rounder. Here's a comparison.

Since I'm older now and my cadence is way down, I may give the rounder one a try.

Too many years since ditching my first-gen Biopace to remember the feel, but Biopace II seems not to draw attention to itself. I just overhauled the spouse's old mtn bike that features a BP crank and have put a few dozen miles on it dialing everything in.

Simple enough to swap in round rings for a comparison. FD adjustment is simpler, too.

Insignificant wear, luckily.

Personally I love biopace cranks

This doesn’t make a lot of sense to me because I have a pretty high cadence and my favorite bike has a biopace triple.

The original bio pace by Shimano. At its best it may help a little, at its worst you can't tell it's there.
Hard to beat Japanese technology.

I also had no problem with Biopace rings and my own high cadence back in the day. But the rings were designed to improve the efficiency of low-cadence pedaling. Evidently some racers got it in their heads that that meant they were no good for higher cadences and complained about them to some bike magazine writers, who went from praising them one year to damning them the next.

By the way, correct that you used the rings as they were designed to be used? I've never seen the point of second-guessing Shimano's research on pedaling ergonomics, but I suppose it's possible that some people might profit from orienting the rings otherwise. Chris Froome used Rotor's more conventionally eccentric rings in at least a couple of his Tour de France wins, so what do I know?

You need to pay more attention. Hogwarts physics and biomechanics are beyond common here. It's truly amazing the number of authorities on this site. Awesome !

I’ll have to check, Ive heard of people rotating them but I’ve never checked to see if mine are rotated, I know the previous owner didn’t change much although he did change the little ring to a 20t.

I just wish that Shimano had made a 50T 130bcd BP. All I've been able to find are 52T and 53T and my aging legs prefer 50T for some unknown reason. I know they are available in 110bcd, but a triple crankset would just look wrong on my Schwinn Aluminum 974.

Someone should make Biopace for current MTB cranks with NW teeth. I'd buy one. The oval ones seem really unscientific, like I'm not convinced the axis angle or eccentricity is based on anything at all except making it look "different but not too different"