Biopace is just as suitable for higher cadences and has some added benefit at lower cadences and higher loads, especially when one is climbing uneven terrain.

If you are bouncing in the saddle then you need to dial in your seat height and work to develop a smooth and efficient spin, if you can feel the Biopace pulsing your pedal stroke is uneven.

They can work really well on a fixed gear to reduce bounce in the saddle under high rpm / load as they effectively de-gear a little during the power stroke which puts less stress on one's knees and allows the leg and foot to maintain speed through the bottom of the pedal stroke.

With the nerve damage in my back and effects to my left leg I find that the Biopace evens out what can be an imbalanced power delivery and when my right leg is working harder my right knee feels less stressed than it can on conventional round rings and I can spin smoother and faster and I do pedal at a fairly high cadence so I can run a slightly lower gear and maintain an acceptable speed.

Before I fragged things I was told I had one of the smoothest pedal strokes one had ever seen and it was something borne of tens of thousands of miles and concious effort on my part to be as efficient as possible. The first time I tried Biopace it did not feel much different as I was spinning in circles already but my knees liked it and found climbing with the mtb was improved.

According to Shimano and Sheldon, they're not:

"The shape of genuine Biopace chainwheels is not a simple ellipse, but a more complicated shape which Shimano describes as a"point-symmetric egg curve." Other crankset makers have made similar designs, generally of simpler shape (pure elliptical) but oriented in a similar manner to Biopace chainwheels. Examples are SR's "Ovaltech" and Sugino's "Cycloid.""

Unless I completely misunderstood the article.
And I still like 'em! They help old guys with bad knees wind up New England hills.

Top

doh! :o

The quoted statement by Shimano and Sheldon does not clarify whether or not the Biopace profile is rotationally symmetric.

I think they are referring to the mounting bolt pattern being symmetric, not the shape of the chain ring.

The biopace ring is rotationally symmetrica with a 180[SUP]o[/SUP] period, but I don't think it would work right if it was on backwards as Top describes. It's hard to describe, but when the crank arm is pointed at the ground, the chain ring has a kind of a flat spot just in front of the crank arm, which makes it easier to pedal it past the weak spot in the stroke. If you flip it around, as Top describes, the flat spot will be behind the crank arm and will reduce power just at the spot where you have the most power to deliver.

At any rate, that's how I understand it. But what do I know.

All that said, I am in the pro-Biopace camp. I have it on two bikes, I think... it is pretty subtle. And I'm a spinner. I have not had good luck with Biopace on non-derailleur bikes.

"My Cycloid does not have an oval pedal path, the pedal path is circular. Just the chain rings have a "oval/ elliptical" path."

Quoted from a previous post. This comment is spot on. Your pedals don't move in an elliptical manner, only the chainring does. This produces a sensation different from round chainrings, but your feet are still pedaling in a circular path. The center of rotation is the spindle.

Personally, I like them and as stated by many posters I can barely sense the difference. But I like the results. Your results may vary.

I can't think of a way to achieve an oval pedal path, not that I'd want to.

I enjoyed the BioPace II rings for over a decade on a Tri bike I had set up for cross, with narrow knobbies and a MegaRange rear cog. The BP rings made the frequent exercise of "mash,mash,mash" to summit a short but steep rise in the trail or dig through a sandy wash much easier than round rings. I feel I was getting a lot more torque more quickly than round rings would have given over this kind of power stroking in a short distance. But after I moved away from those easy trails and had to start riding the road more with that bike I swapped them out for round rings and road gears - the change was instantly noticeable and I don't think I could go back to the BioPace now, at least not on that bike and not for riding on the road.

Don't have an opinion on the OP's original question about rotating the mounting of the BP rings, but I can affirm that not all BioPace rings were the same shape. Mine came with the Exage gruppo - a large diameter two ring setup and I have ridden other BioPace 2 and 3 ring setups that were far more "oval" shaped than mine were and had a lot less teeth. Mine felt natural even at a faster rpm, different but naturally rhythmic. Some others were a weird distraction, they made the chain pop up and down slapping the chainstay and were difficult to me to shift the front derailleur accurately when peddling fast.

So if you are looking for BioPace rings, I would suggest you try a couple of different models - the BP2 in a larger diameter I can recommend for sure.

As you state, Biopace chainrings are 180 degrees rotationally symmetric and the major axis is is skewed slightly from the crankarm axis to faciliitate travel through the top and bottom of the stroke.

Based on the pics, Top506 has simply rotated the chainrings 180 degrees, as necessitated by the spider orientation. Since his spider is 180 degrees out of phase to a Shimano spider and the Biopace chainrings are 180 degree rotationally symmetric, he will experience the exact same stroke mechanics as intended by the Shimano engineers.

Since Biopace is not elliptical there are two ways to alter the stroke mechanics. You can rotate the rings in 72 degree increments and/or flip the rings. The latter will produce the effect you describe, causing the major axis to be skewed an equal amount form the crankarm axis but in the opposite direction.

The bottom line is that Biopace chainrings are 180 rotationally symmetric, despite the fact that they are irregularly shaped and are not symmetrical about the crankarm axis. Changing the orientation (by anything other than 180 degrees rotation) does alter the stroke mechaincs but the stroke will be identical for every half revolution. To do otherwises, would submit the left and right leg to different loads at the same point of rotation. No competent engineer would do that.

T-mar, well stated.

Roger that! Clears things up nicely.

Top

:thumb:

I misunderstood something along the way. I stand (okay, sit) corrected. I won't even bother to explain what I misunderstood! Carry on....

I just did a test ride on a single speed with a 48t biopace ring (yellow label which i think is the first edition) and at high cadence i noticed that it definitely felt like I wasn't getting as much power as I should have been. i felt like I needed to pedal straight up and down more than "in a circle". It feels like the spot where you have to push the hardest has been "smoothed out", but you don't get as much power in return.

I'll try rotating it, see how it feels and report back.


Though honestly if someone wants to trade for some round rings shoot me a PM, i've got a yellow label 48/38/28, a biopace HP silver label 46/36/26 (both are 110bcd came on deore cranksets) and black label 52/42 (130 bcd came on a 600EX crankset). all nice quality aluminum rings. would love to trade for compact double rings

Apparently they need to be rotated two bolts, -144 degrees, because were originally 50 degrees out of phase from having having the biggest gear in the dead spot (approx -140 degrees away from Q-Rings).

Why are you replying to all these dead threads about Biopace? :wtf:

When one Googles for the information regarding the use of Biopace as rotor q-rings, one is directed to these threads which are act thus in a way similar to specialised wikipedia pages providing solutions to in-depth problems. I hope someone who, spending some time Googling like me, finds the information regarding the rotation of Biopace to act as Rotor Q-Rings useful. There are still a lot of Biopace around, at about a one 10th of the price.

1/10th of q rotors? Should be able to get em cheaper than that.

Yes, sometimes the price differential is more like 20 or even 30 times so the information that Biopace may be (according to my calculation and Barchettaman's testimony) very similar if rotated 2 bolts back may be useful to some thinking of trying a Rotor Q-Ring or other oval chain wheel. I have no doubt that the adjustable, oval Q-Rings are superior, however.

Funnily enough I just listed a pair of Biopace on Ebay last night, then these threads come back around!

I have subsequently gone to compact cranks as I prefer the wider gear range. 50/34 with an 11/28 makes me happy.

Hi Barchettaman!

You are the man (with a couple of others!) . Thanks very much for the advice.

I tend to be searching for a higher gear. Than my 50 will provide. How much are your Biopace?!
I guess shipping would be prohibitive to Japan, and they are going very cheaply here.
(I don't think I want to swap since I may want to swap back to the compact crank.)

Here is your advice pictorially. The second picture is from a Shimano Biopace advert.

I take the liberty of adding a red arrow to your photo.
https://farm8.staticflickr.com/7548/...d3786b37e4.jpg
"Rotarized Biopace" Barchettaman's Crank Position Rotated 144 Degrees by timtak, on Flickr

https://farm8.staticflickr.com/7492/...5fff58e7d2.jpg
Biopace Crank Position by timtak, on Flickr

The Biopace chainwheel was a smoothed rhombus with the crank at the one of the corners at the start of the longest part of the crank of the long part of the oval if the crank where oval. According to Highpath Engineering : EGGring oval cycle chainrings - page 3 Biopace were 50 degrees forward of the shortest part of the oval (I have added that 50 degrees in very small letters to the above diagram).

Today's O Symetric and Rotor Q-Ring cranks typically have the crank at about the the narrowest part (or 3 degrees before) of the chainwheel, as can be seen in the photograph below
https://www.flickr.com/photos/chriscallanan/4618126366/

In other words, the crank needs to be rotated about 50 degrees rearwards, or (180-50 =) 130 degrees forwards, or the chainwheel 130 degrees backwards.

There are five bolts on the chainwheel, so moving the chainwheel two bolts, and 144 degrees backward, as Barchettaman advises, will move the crank 144 forward. This is a bit further than the middle of the small part of the oval rather than a bit before as in the O-Symetric set up. I am not sure what this means.

I tend to pedal with extended ankles through the bottom of the stroke, rather than pushing over the the top of the stroke. From reading the Q-Ring optimisation page, I think that having the cranks rotated forwards may suit my over extended, push through the bottom, ankle style but I am not sure. It may be the reverse!

Rotating the crank forward (chainwheel back) by 144 degrees should mean that crank is 14 past 3 o'clock at the top of the oval (if Biopace were oval). According to the following post at stackexchange
Revisions - Bicycles Stack Exchange
14 degrees past the horizontal in the middle of the narrowest part of the oval, is actually a little less past horizontal than the Q-Ring in its recommended start position "3" which is 18 degrees past horizontal apparently.

Thanks again.

PLEASE.
Let these biopace chainrings rest in peace.
This fad comes around about ever 50 years......... like 3D at the movies.
There is a reason they are so cheap on ebay.

I don't mean to resurrect Biopace (though they have their proponents in some situations: touring and unclipped urban cycling), but there is also a reason why Q-Rings are so expensive on ebay. I am suggesting (following Barchettaman's advice) that two-bolt rotated, "Rotarized Biopace" can approximate to rhomboid, non-adjustable, so not as good, but very cheap, Q-Rings.

Highpath Engineering explains the merits of Q-Rings and why Biopace have problems here.

Um, just because?

I noticed that in the pics in the opening post the crank arm is pointing up in one and down in the other. That could make a difference. If you switch the orientation of one arm by 180deg but not the other you might end up with a very weird pedaling motion. But then, perhaps some people wouldn't feel the difference. :D

Because I thought it important imho to have information on rotating Biopace chainwheels to mimic Q-Rings in one thread.

IThe 180 degrees does not matter since it is the rotation of the crank arm to the chainwell that is important, not its alignment in the photo. But this is difficult to see. So, please note the position of the small nodule in the lower photograph, that I have emphasised at the start of the red line here below (likewise it does not matter that in this photo, the crank is now pointing to the right).
https://farm8.staticflickr.com/7548/...d3786b37e4.jpg
"Rotarized Biopace": Barchettaman's Crank Position Rotated 144 Degrees by timtak, on Flickr
Ordinarily this nodule would be behind the crank but the chainwheel has been rotated backwards two bolts (144 degrees), which means the crank has been has been rotated forwards two bolts/114 degrees.