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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 04-14-07, 01:42 PM   #1
daveed 
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Does Sheldon recommend biopace ...

...chainrings for fixed gear bikes? I recall he wrote something but can't quite remember if he was a biospace proponent. Not incidentally, I put one (44t) on my bike yesterday and rode it around the block. No problems, though I haven't figured out (yet) how it's going to help. The ring looks cool nonetheless.

Anyway, just wondering if I'm doing myself any favors with this new chainring.
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Old 04-14-07, 01:54 PM   #2
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There are claims that it's good for the knees, and yes it can work on a fixed gear.
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Old 04-14-07, 02:02 PM   #3
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sheldon is a biopace proponent if there ever was one, check out his bikes and you will see biopaces on almost every bike
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Old 04-14-07, 02:17 PM   #4
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Quote:
Originally Posted by freeskihp
sheldon is a biopace proponent if there ever was one, check out his bikes and you will see biopaces on almost every bike
Well, then, here goes ...

Thanks.
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Old 04-14-07, 02:52 PM   #5
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I ride biopace.

It helps on hills and I can spin a little faster.

Strangely, a biopace feels "rounder" than a round ring.

Shimano might have meant a 44t biopace ring as a middle or inner ring on a multi-chainring geared bike.

If so, Daveed might consider flipping the ring over so the chainring bolt countersinks go up against the crank star.
Biopace rings have a "direction," and, if an inner ring (sounds like it), this will correctly orient the ring.
I ride with my 42t biopace ring oriented this way, and it works great.

By the way, having the countersinks against the star gives more room around the chainring bolts for centering the chainring.
Taking extra time to center the chainring lets me tighten the chain more, so that it gets almost tight at the tight places and not too slack at the slack places.
The tightest place should occur with the top pedal at about the 12:30 or 1:00 position, a little ahead of the seat tube.
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Old 04-14-07, 03:27 PM   #6
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Quote:
Originally Posted by Ken Cox
Shimano might have meant a 44t biopace ring as a middle or inner ring on a multi-chainring geared bike.
Yes, the 44 was for the middle of the "touring" 110/74 mm set: 50-44-28.

Quote:
Originally Posted by Ken Cox
If so, Daveed might consider flipping the ring over so the chainring bolt countersinks go up against the crank star. [spider]
Yes, if you mount it on the outside of the spider, you should do it that way. It was originally intended to go on the inside of the spider.

Sheldon " http://sheldonbrown.com/biopace " Brown
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Old 04-14-07, 03:30 PM   #7
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i dont like the way biopace look when they are spinning...the chain flapping and all.
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Old 04-15-07, 11:53 AM   #8
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Quote:
Originally Posted by cosmo starr
i dont like the way biopace look when they are spinning...the chain flapping and all.
First, thanks to Ken and Sheldon for the useful advice. I'll flip the ring. As for Cosmo's remark, I must ask: aren't riders supposed to keep their eyes on the road?
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Old 04-16-07, 04:52 AM   #9
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I'm going to give this a try. Question: I have a 42 tooth biopace ring. It will be mounted on the inside of a double crank. Which side of the bike should the writing on the ring be visible from?
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Old 04-16-07, 04:55 AM   #10
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Quote:
Originally Posted by MKRG
I'm going to give this a try. Question: I have a 42 tooth biopace ring. It will be mounted on the inside of a double crank. Which side of the bike should the writing on the ring be visible from?
Does this ever matter on a fixed gear.
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Old 04-16-07, 04:57 AM   #11
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Biopace are not round and they are "directional", so...yes.
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Old 04-16-07, 05:31 AM   #12
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Quote:
Originally Posted by MKRG
Biopace are not round and they are "directional", so...yes.
I got the not round part, how are they "directional"? As in how does mounting it one way or another on a fixed gear one chainring bike matter?

Honest question, Sheldon only says this about mounting:

Quote:
For installing Biopace chainrings, the orientation should generally be preserved. Each Biopace chainring has an "indexing mark." This is a small tab pointing inward toward the middle of the chainring.
For the record, i've tried biopace on fixed gear and the variation in chain tension is just a bit too disconcerting in regular use.
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Old 04-16-07, 06:29 AM   #13
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Because the biopace makes it easy in one part and hard in the other. If you dont preserve direction, you may make it hard in the part of the pedal stroke that is already hard.

But on a fixed gear, your feet should always be tightly strapped to the pedals. I love biopace for platform pedals, on bikes where you need a bit of help to get through the weak spots in the stroke. On a fixed, it is rather silly.
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Old 04-16-07, 07:47 AM   #14
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Quote:
Originally Posted by genericbikedude
Because the biopace makes it easy in one part and hard in the other. If you dont preserve direction, you may make it hard in the part of the pedal stroke that is already hard.
Guess i'm just dense. I don't get that.
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Old 04-16-07, 07:53 AM   #15
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Quote:
Originally Posted by genericbikedude
Because the biopace makes it easy in one part and hard in the other. If you dont preserve direction, you may make it hard in the part of the pedal stroke that is already hard.

But on a fixed gear, your feet should always be tightly strapped to the pedals. I love biopace for platform pedals, on bikes where you need a bit of help to get through the weak spots in the stroke. On a fixed, it is rather silly.
I'm pretty sure they are elliptical though. Therefore as long as you oriented it properly flipping it shouldn't matter and therefore the writing shouldn't either.
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Old 04-16-07, 07:55 AM   #16
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AFAIK they are not perfectly eliptical, but rather a warped elipse. There is also suntour's OvalTech. Far cooler, IMHO. Both used some form of complex analysis to figure out where the radius should be larger, and where lower. I think it is more complicated than just a simple oval.
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Old 04-16-07, 09:00 AM   #17
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I'd say Sheldon is a Biopace user. Yes, I read that he has used it on fixed gear bikes. I'd stop short of saying he "recommends" it for the general cycling population. I've never seen him do that.

There are some aspects of my bikes that I enjoy, but would never recommend to others because I realize it isn't very mainstream and most people wouldn't care for it.
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Old 04-16-07, 01:01 PM   #18
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I used a 42t biopace. While I loved the pedaling it provided, I certainly did not like the chain falling off when the BB flexed too much and gouging the crap out of my chainstays. got a 43t round dura ace ring, and nary a chain dropped since.
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Old 04-16-07, 04:37 PM   #19
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The chain tension shouldn't vary at all with the 'right' biopace rings (1st generation I believe). Sheldon addresses this in length, but the short of it is one generation of biopace works great, others give you tension issues. I believe the OvalTechs are also a no go. I'd have to do some more digging ... Anyways, try it. If you get more than normal variations in tension, it's probably best to go back to round chainrings.
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Old 04-16-07, 05:05 PM   #20
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This came up on a thread in the commuting forum too. I've got a 42t biopace chainring that I'd like to try out... but how do I tell if it's 1st generation? Where would you suggest digging SSS? I've done the biopace search for this forum to come up with a quote for the commuters, but didn't turn up anything more useful than: yes, it sometimes works well, and Sheldon does reccomend them.

or, I suppose I could just try it and see that way. Time to tinker!
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Old 04-16-07, 06:21 PM   #21
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From my experience, the Ovaltechs will NOT give an even chain tension. I built a single speed for my wife on a bike that came with a 42 tooth Ovaltech as the inner ring. At one point of the rotation, it would be bordering on completely binding the chainring, while at another point it would be so slack that you could see the chain bouncing around. Currently, I'm running a chain tensioner on them, and you can see the range that the arm has to cover as she peddles the bike.
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Old 04-16-07, 07:32 PM   #22
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Hmm ... I can't find any information about the generations at this point. I'm not sure where I read that. Best bet is to give it a try. Sounds like you've got it working at this stage. Good on ya.

If you've got old biopace, your only option is probably to just try it. I am of no help.
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