Review - Shimano Biopace Crankset
 

Figured I'd give one of these oval chainring setups a try. Its a shame that these never quite picked up on the market.

https://cimg7.ibsrv.net/gimg/bikefor...79f78cc01e.jpg

While the smaller chainring is more subtle, its effect becomes particularly noticeable when you shift to the larger chainring. It feels weird at first, but your body quickly adapts and learns how to make the most out of the change and crank rotation.

When pedaling on regular circular chainrings, you might find that the top half of the pedal stroke puts you into a more effective position to crank out some extra power versus going from the bottom half back up to the top. As such, the cranks actually move faster down than they do back up.

as such, the chainrings increase in diameter at the top half of the stroke, and then decrease at the bottom half. The end result is that power delivery is noticeable smoothed out - it is now one, smooth continuous movement, taking full advantage of the powerful part of the pedal stroke and "conserving" this energy in order to speed up the crank revolution through the less efficient area of the pedalling stroke.

While it is rather subtle in the smaller chainring like I said, in the larger one I feel noticeably more efficient and definetly a little bit faster. The sensation is almost as if the cranks are pedaling themselves when you are rolling on smooth pavement. Its a very natural feeling that's gentle on your knees and apparently helps to increase the blood flow in your legs. Im definetely quite happy with these compared to my original Sugino circular crankset.

Oval rings are an age old idea. There must be a reason they keep failing in the marketplace, get reintroduced as new and improved and fail again. Failure is not bad in this case, it simply demonstrates market demand was not enough to sustain the idea. Biopace came on two of my mountain bikes back in the 80's and after experiencing knee issues with them, they were replaced with round rings, which leads me to believe each user reacts to them differently, which goes to demonstrate that no one thing is the right thing for all users. Glad you like them!

I think that was mainly due to how they were marketed.

Perhaps the crank arms were not the right size according to your inseam. I've heard lots of different people stating how easy they are on the knees.

I understand that its not for everyone though. Maybe you just pedal at a higher or lower cadence than what these oval rings are designed for? I find that they work best at a specific cadence. Could be why.

My 1984 Nishiki International Ole's large front cog is oval (I replace the smaller one with a smaller circular one for our Colorado hills). I never think about it until threads like this. Perhaps it is not oval enough, but I can't feel any difference between it and my other round-cogged bikes.

The design of earlier iterations of oval rings was based on the assumptions that racers would benefit from increasing the gear ratio in the section of the pedaling circle used for applying power and decreasing the ratio in the other sections and that the sky's the limit for the eccentricity of the chain ring.

Shimano's marketing department (I'm guessing here about the origin of their approach, but it was someone pretty smart), having noticed that the vast majority of riders buying racing-style bikes in the early '80s were sport riders, asked Shimano's engineers to come up with an improved design for non-racing riders, who tend to use lower cadences than racers. Thus, the egg-shaped oval chain rings with two focus points.

They failed in the marketplace for one primary reason: Shimano proceeded to spec BioPace rings throughout their component groups, and while the sport riders were generally happy with them, racers hated them for their lumpy feel at high cadences. Guys writing for bike magazines heard their racer friends complaining and damned the rings to the depths (having praised them to the skies when they were first introduced).

Biopace and modern oval chainrings are not the same thing. Biopace had the clocking of the "oval" wrong and made the gearing lower in the strongest portion of the pedal stroke and higher in the weakest part of the stroke. This put more stress on your legs and joints at the point where they were least prepared to deal with that stress. https://absoluteblack.cc/home/menu-1...20rings%20work.

I dont understand the purpose of spinning in such a high cadence though. It simply means you are not in the right gear, and that you're spending more energy going slower... or perhaps the bike isn't geared right for your needs. Or perhaps the crank arms are too small for your legs.

At any rate, i think a racer can also benefit from this tech..

From looking at my crankset, (I have two biopace sets)

The chain rings defientrly increase in diameter at the stronger part of the pedal stroke, not the other way around.

I seem to keep getting bikes with those things, I give them to the co op.
Tim

Then someone has clocked them differently than they were intended. In your pic above, the small ring has been clocked one bolt hole off as evidenced by the small tab that should be aligned with the crank arm.

​​​​​​​You don't understand a lot of things, but you go on giving advice as if you do. What cadence do you think is efficient? My most efficient cadence is between 93-105rpm for road riding

Had a bike with them once, decades ago. Don't know if it was biopace or some other oval, but found I prefer regular round chainrings. The ovals just felt too much "off and on" (for lack of a better description) to me. Gave the bike to my brother-in-law, who doesn't ride a lot, but still takes it out occasionally.

From an engineering stand point, the whole idea is completely flawed. How many things that rotate are other than a circle?

comparing modern oval rings to Biopace. how original!

At least you are to the point of saying you dont understand. This is progress.

Are we still putting hot air in this guy’s balloon? His cover was blown a month ago

That doesn't seem to be deterring anyone from posting here, though.

Someone opined in an earlier post that Shimano got the clocking completely wrong. It's true that BioPace is inappropriate for racers and others maintaining cadences of 90 rpm and above (which is what Rotor Rings, etc., are designed for) but not for casual riders and many sport riders, who tend to go for lower cadences of 60 to 80 rpm or thereabouts. Those are the riders who can benefit from BioPace rings, and there are a lot of those riders out there.

The bike I ride the most has Biopace chainrings, just to make it more odd and irritate bike snobs.

My first mountain bike and bike that I bought with my own money was a 1990 Giant Sedona that was shod with Biopace chainrings. I replaced them within a year for round rings. The pedaling was just weird. Fast forward to 2009-ish and I took a gamble on oval Rotor rings on my Salsa. Way better and smoother power delivery. Shimano could have developed Biopace a little more. I now have two other bikes with oval chainrings - Wolftooth and Absolute Black and they're both great.

The current round of oval chainrings for single ring MTBs are not failing in the marketplace. They continue to be pretty well received.

The effect is 'more subtle' in the smaller chainring because you've mounted the smaller chainring wrong. See that little nub on the inside perimeter of the small ring at around 5:30? That nub should go under your crank arm.

A lot of people misunderstand the reason behind the Biopace design. Intuitively you would think you want higher gearing where your leg is strongest (around 3 o'clock), and lower gearing where your leg is weak (12 and 6). If you are seated and grinding at a very low cadence, this is true. However, if you are either standing, or spinning, what ends up happening is that you will typically 'overstomp' 6 o'clock. Meaning you continue to stomp downwards even at or past 6 o'clock. When you are spinning very fast, like going downhill, sometimes you can feel your butt bouncing off the seat with every stroke. This is because you are overstomping 6 o'clock. That wasted energy goes to lifting our butt off the seat. Same with standing and pedaling. A lot of times you have to consciously tell your feet to 'lift up' at 6 because the tendency is to stomp the pedal into the ground. Biopace was designed to counteract this tendency by increasing the resistance when you get close to 6 o'clock.
Of course, Biopace is useless for pro riders who have perfected their circular strokes and never overstomp 6 o'clock. That would be 0.005% of the riding population. The rest of us definitely benefit from the genius of Bio-pace.

Shimano put tons and tons of development effort into Biopace.

Thank you for pointing that out..

optimal cadence is dependent on a number of factors. I think past 105RPM means you're in too low of a gear, as it becomes more difficult to efficiently trasnfer power past this stage.

So you think that Biopace can be used as a learning tool? Perhaps for switching back to circular chainrings in the future? Or do you think that Biopace is simply superior due to its design?

I would imagine that some types of more serious competition cycling could also benefit from this design.

Thank you. Will orient it correctly and give that a try.

I had one way back when it first came out. I rode for 3 years with medium fast groups and lots of miles 6,000 a year. It didn't slow me down or anything negative but I don't think it helped in any way either. It was just something different that I was trying. The only thing I remember is that it never felt good to spin and I didn't spin much anyway. After 3 years the experiment was over and gone. I would never recommend that anyone get an oval chainring, it does nothing.

This is curious behavior for a hobby. Someone has to fight those windmills though!

"clocking" = 90° out of phase.