Rotating biopace rings
 

I don't really like biopace.. i just don't "trust" the technology, and I've read some things that suggest is it actually less efficient than normal round cranks. Unfortunately, right now I have a wide selection of BP rings, and no round ones.

I've heard claims that if you rotate the biopace rings by a few bolts, they are more efficient/effective. This is a suggestion I found:

Normal
http://i271.photobucket.com/albums/j...tures001-1.jpg

Rotated
http://i271.photobucket.com/albums/j...tures002-1.jpg

Has anyone done this? Are there noticeable results?

I can't help you on whether or not rotating the rings make any difference, but I will say I love my Cycloid (Sugino's version of Biopace) rings. Just seems to help take off a little bit of the "edge" while climbing or on start up.

Older riders seem to favor them. I actually can barely tell the difference. It's like that with mashers.

When I got my Voyageur a few years ago I discovered the BioPace rings were out of phase. I don't know how efficient or inefficient the incorrect alignment was, but it felt incredibly weird to pedal with the odd configuration. After I aligned them correctly I found that I really couldn't tell the difference either - at least not after I'd gotten used to the oval pedal stroke.

I honestly don't know if I could tell in a blind comparison between round and stock biopace.. but after that one thread I saw which suggested they might be less efficient, i'm always going to be thinking about it hahaha

I do kinda feel like I lose a tiny bit of power in certain parts of the stroke, but it could all be in my head. I have some Biopace HP rings which are more round which I plan on swapping onto my Univega, but I was wondering if I should do the "biopace rotation trick" at the same time

I think the idea of rotating Biopace is to get the effect of modern ovoid chainrings (Rotor Q-Rings and O-Symmetric). The newer non-round rings make the biggest gear when the cranks are at their biggest leverage advantage, so the "peak" of the oval will be at 12 o'clock when the pedals are at 9 and 3 o'clock. This is sort of the opposite of Biopace/OvalTech/Cycloid etc. that all put the "peaks" (and therefore bigger gear) equal with the pedals. They intended to help overcome the "dead zone" where the cranks were vertical and riders have little mechanical advantage.

I've ridden both. Biopace feels a little odd when spinning. You get that pulse pulse pulse pulse effect. When mashing, or climbing, I didn't notice it as much. Q-rings, on the other hand, don't feel as unnatural. They felt smoother when spinning, and again, I didn't notice any difference when mashing/climbing.

Biopace and Q-rings are off by 90*. Because there are 5 holes on the Shimano cranks, you can't get exactly 90*, but 72*. Close, but I have heard from a tinkerer friend that it is just off enough to feel distractingly weird.

Biopace was originally designed for the tourist and recreational rider. As suggested, the primary intent was to smooth out the pedal stroke for such cyclists, increasing their efficiency. It also produces less stress on the knees of such cyclists by producing a more distinct difference between the extensor and flexor phases as the top and bottom of the stroke. Biopace does exactly what it was intended to do, when used as intended. It's intent is not the necessarily the same as other non-round chainrings, so rotating them will give a different effect. It all depends what you want out of your chainrings.

Biopace was also produced in varying degrees of non-circularity (it wasn't actually an ellipse) depending on the application. Generally, smaller chainrings had a greater Biopace effect. The Biopace effect was also reduced on higher level components, where it was assumed that owners had learned a smooth pedal stoke and there was more individuality. For instance, Biopace was never a Dura-Ace option and it was relatively mild on the 600 series. This may be one reason for the varying reported "effects" of Biopace.

I agree with T-Mar, in their intended application Biopace work well and the general concept of non-round chainrings is very well accepted in cycling. There's no reason to not trust it.

Back in the day our #1 complaint from customers is that they'd bounce in saddle at high rpm, those customers were racers and many simply changed out the big Biopace ring for a round ring. In subsequent years Shimano toned back the Biopace effect, I think the new rings were marked as Biopace II and were more round.

Funny how things always seem to work that way :)

This sounds like a case of the original fact being progressively exagerated each time it is retold. The original 38T and 48T chainrings were designed for 55-100rpm, while the 28T granny was intended for a maximum 80 rpm.

We always advised if you were a 60 to 70 rpm kind of guy, Biopace was good, even more so if you did not use toe clips and straps.

When I bought my first mtb, I had the shop toss the big biopace ring, kept the two smaller ones, worked well and still does.

:eek:

Rotating the rings effectively turns them to the Rotor rings. The purpose to Rotor rings is to increase torque on your downstroke. For biopace, it is to increase torque at 6/12 because you have more momentum at the bottom/top of your stroke.

I would like to barrow that!

http://i219.photobucket.com/albums/c...198/WTF003.jpg

I read both abstracts and it sounds like those guys know what they're talking about. However, I take their findings with a certain grain of salt; i.e. they may be correct but I'm not 100% convinced. Their investigation is very esoteric; and if it were my field, I would be able to recognize the validity of their methods and assumptions; but since it is not my field of expertise, all I can recognize is that their findings rest heavily on the correctness of their methods and assumptions. If the papers were peer-reviewed, with general buy-in from the reviewers, that would make a big difference to me.

Anyway, thanks for the link. The article abstracts were very interesting and enlightening.

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

so... who's actually tried it? ;)

No, wait,... I've seen it in the cartoons, when the Roadrunner gets his legs really really revved up, they describe an elliptical path... ;)

After ACL replacement and meniscus grafts in both knees, I can say that BioPace chain rings have made it more comfortable to ride and have actually strengthened my knees! Of course, I've been using them since they were first introduced so I've always been sold on them. Oh, and BTW my cadence averages around 95-105 RPM.

frantik - I would keep the alignment marks right where they're designed to be. If you cannot get 'used' to them, then swap them out for round rings.

Just my insignificant opinion here, but rotating BioPace chain rings for 'better' efficiency... What, don't trust the original designers' R & D?

:I

On a serious note, all mammals' feet make an elliptical path when walking or running. The stride is invariably longer than the lift, unless a conscious effort is made to do otherwise. Only when we restrict the natural gait by mechanical means, do we impose a circular motioin. Be it a roadrunner or a Old's Cool, we naturally make ellipses.

I've rotated Biopace chain rings 180 degrees to make them work with a Sugino crank. The spider was oriented 180 degrees away from the Shimano crank. I figure all this did was switch the primary power stroke from the right pedal to the left.

http://i128.photobucket.com/albums/p...506/cranks.jpg

And count me among the fans of Biopace!

Top

By this you are insinuating that Biopace rings are not rotationally symmetrical with a 180deg period, i.e. the cam profile does not repeat every half revolution. Is this true?

They're symmetric. He's pulling your leg.

Me too! Last summer I got a bike with 1986 Shimano 600 Biopace. I prefer Biopace now.

For me, I have always had a negative feeling towards the Biopace. There is no logical explanation for this. That said, I recently started riding a triple Biopace rig, a Gary Fisher "Hybrid" that I picked up recently.

Though the "Hybrid" does not look or feel "vintage" to me, it is a treat to ride. Also, I have been consciously considering the Biopace performance as I ride. So far, I like it but to know for sure that it is the ring design I like is tough to say. I would have to swap out crank rings and then ride. My guess is there will not be a huge difference, but you never know.

http://bikeforums.net/attachment.php...hmentid=279363 http://bikeforums.net/attachment.php...hmentid=279364 http://bikeforums.net/attachment.php...hmentid=279365

Either way, the Gary Fisher will remain as issued and "as found". I really like riding it.


As for the Durham, I owned a Motobecane Mirage fitted with one a few years ago. Actually, I got rid of the bike last Fall. Anyway, at any rpm over slow would cause the bicycle to bounce a bit...

http://bikeforums.net/attachment.php...hmentid=279366 http://bikeforums.net/attachment.php...hmentid=279367 http://bikeforums.net/attachment.php...hmentid=279368

I really did not like riding the Motobe!