The myth of Biopace... Let's discuss

[andrewl]

Yes those are the ones I was thinking of. Have photos in a book of other early ones too.

 

[andrewl]

Have to sayi love Egg rings, made by Chris Bell. I also loved biopace when I was a kid because I couldn't afford Chris' rings and you could just rotate them 90 degrees and they worked properly.

Assume you mean approximately 90 degrees as a 5 arm crank makes 90 degrees changes a challenge

 

[dbmtb]

I didn't like how they limit the number of possible chainring options due to front mech rub. Thats why I stopped using them.

 

[merckx]

Here we go, 1893:

http://www.oldspokeshome.com/columbia-model-“32-1893

Even these guys got the orientation right, how did Shimano think they were right.....

wild! i think they might have over engineered the saddle rails somewhat however.. :shock:

 

[velomaniac]

Most of the knee knackering hoohaa came from the roadbike crowd who were using oval rings before biopace with the longitudonal axis not in line with the cranks. Old style road oval rings were to a degree worked out in shed engineering without much scientific application plus roadies turn bigger rings which of course put more strain on the knees. So when Shimano came out with Biopace the roadies just shouted out how crap oval rings were.

Shimano however did a great deal of scientific and engineering studies of mechanical efficiency and ergonomics. When the crank is at the high point you have the most potential power you can put down and when at horizontal the least. Thus when climbing up a hill on loose terrain when your power has dropped as the cranks become horizontal your effective gear drops aswell thus compensating for the power loss.

I think Shimano had thought it out well its just prejudgemental roadies shot it down before it had a proper chance to prove itself.

I like the principal but to be frank I dont notice the difference but this is the case with most techy inovations. The difference must be really significant or I dont notice :roll:

 

[al]

Poo!

al.

 

[bm0p700f]

I use them on one of my single speed MTB and I like the way it rides. I do find the 38:16 ratio I am using easier than I expected on the hilly parts of Thetford Forest given the ratio.

I quite like the idea but I think it was victim in part to Shimano's over technical sales pitch. They apparently gave the they only work at a cadence of 90/min which is not true. There is a good write up of oval/biopace rings in Bicylcle Science 3rd edition a Physics text book for bikes - brilliant.

 

[Rich Aitch]

Most of the knee knackering hoohaa came from the roadbike crowd who were using oval rings before biopace with the longitudonal axis not in line with the cranks. Old style road oval rings were to a degree worked out in shed engineering without much scientific application plus roadies turn bigger rings which of course put more strain on the knees. So when Shimano came out with Biopace the roadies just shouted out how crap oval rings were.

Shimano however did a great deal of scientific and engineering studies of mechanical efficiency and ergonomics. When the crank is at the high point you have the most potential power you can put down and when at horizontal the least. Thus when climbing up a hill on loose terrain when your power has dropped as the cranks become horizontal your effective gear drops aswell thus compensating for the power loss.

I think Shimano had thought it out well its just prejudgemental roadies shot it down before it had a proper chance to prove itself./quote]

Biopace are marvellous, they changed the phasing to reduce knee strain- http://sheldonbrown.com/biopace.html -I have one leg shorter than the other, yes yes, I know everyone does but mine are more so and have suffered leg probs in the past after riding bikes with round rings. However when I'm on my Biopace SG equipped Marins I can outclimb most people and no problems.

If you are someone who has tried Biopace and it's damaged your legs check the alignment of the chainrings on the cranks to make sure some doofus former owner hasn't changed the phasing to "Improve" it.
Other manufacturers who made non-round chain rings with Biopace phasing were Sugino [Cycloid] and Sakae [Ovaltech].
Here are some Ofmega oval touring jobbies that I picked up but haven't had chance to tinker with yet. Although Ofmega weren't a Biopace licencee as far as I know they look to me like the phasing - if not the shape, which is too regular- is in the same plane as Biopace. What do you think?