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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 07-07-04, 08:38 AM   #1
rykoala
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SS with BioPace rings?

Is it possible? I am getting my old Trek 820 back and as I recall it has biopace rings on the front. Will this work or will I need a standard round ring? Thanks for the info.
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Old 07-07-04, 09:08 AM   #2
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In theory it should work. The idea is that only half of the chain ring is in contact with the chain at any givin time so tension should not change. This is from Sheldon's site ( he loves biopace). In practice, when I helped a buddy of mine build a SS with biopace and a singulator you could see the tension change throughout the pedal rotation.

So back to your question, it depends on your bike. Are you using a chain tensioner of some kind or do you have horiz dropouts?
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Old 07-07-04, 09:09 AM   #3
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were the rumors of biopace trashing knees bunnk then? I heard too many of these types of rumors
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Old 07-07-04, 09:14 AM   #4
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Well, I've heard those rumors too. LBS hates them, says they blow out knees. I've never had a problem and I've had 3 bikes with biopace rings. But I'd be lucky to be over a few hundred miles, not a few thousand. So over the long run I don't know.

I will see the bike tonight and will know what kind of dropouts it has then. The bike has a bent derailer hanger (that's why its going SS) so I'm trying to avoid a tensioner. I suppose an easy way to tell is to watch the derailer on my rock hopper, it has biopace rings too. If the derailer moves, then I'll know. Right?
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Old 07-07-04, 09:29 AM   #5
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The only complaints my buddy has with his is high RPM's are difficult. I'll ask him about his knees.
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Old 07-07-04, 11:24 AM   #6
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My SS coaster brake has a Biopace chainring. No problems. There is a little variation in chain tension as the cranks are rotated. However, to put it in perspective, I personally have never seen a non-Biopace SS setup that didn't have a comparable amount of chain tension variation (this includes cruisers, three speeds, BMX and kids bikes).

Why do I use one? Because it came on the cranks I used. I've owned two different bikes with them, and I can say, I've never noticed any appreciable difference between Biopace and normal rings. I think this was one of the instances where the science is pretty shakey but didn't deter the marketing dept. Meanwhile, adherents and detractors make up their minds based on anecdotal, uncritical and irreproducable results.

There are at least a couple testimonial accounts in favor of Biopace chainrings:
http://sheldonbrown.com/biopace.html
http://www.bikexprt.com/bicycle/mytwenty.htm
Also, both these sites describe Biopace equipped bikes that use no derailers or tensioners.

Interstingly, I've heard from some users that they're good for their knees. This thread is the first time I've heard bad anecdotes about them. Most opinions I've heard are more like mine: they don't seem to make much difference.
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Old 07-07-04, 12:02 PM   #7
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biopace was engineered to be most effective at 90rpm cadence. its supposed to compensate for the lower power transmission when the cranks are in the vertical position. when pedaling at 90rpm the biopace rings should be fine for the knees, but at significantly higher or lower rpms they may be damaging to the knees. so if you're on a SS/fixed you would be riding at such a large range of different rpm's it would probably be a bad idea for the knees.

ive switched between bikes with and without biopace, and i think that its easy to feel the difference. i really do think they feel good when pedaling at 90rpm, but still wouldnt want to have them on my bike permantly.
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Old 07-07-04, 12:38 PM   #8
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BioPace is crap
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Old 07-07-04, 12:41 PM   #9
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Well, looks like it'll start out w/ biopace rings until I get a few bucks to go buy a standard round ring. Thanks for all the input, I really appreciate it!
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Old 07-07-04, 01:32 PM   #10
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Quote:
Originally Posted by [165]
were the rumors of biopace trashing knees bunnk then? I heard too many of these types of rumors
from sheldon's site:
Quote:
The theory is that during the power stroke, when the cranks are more or less horizontal, you are using the power of your legs to accelerate your feet, which get going quite fast in the lower gear provided for that part of the stroke. The momentum of your feet then carries the pedals through the "dead spot" when the cranks are near vertical. Since the rider doesn't push as hard during the power phase of the stroke, and motion is slower when the leg is changing direction, the Biopace design is gentler on the knees than even round chainwheels.
i'd have to say, yeah, it's bullsh!t. if you read the article on sheldon's site, it says that biopace rings are oriented to to the opposite of traditional elliptical chainrings
Quote:
Biopace chainwheels have the small radius engaged when the cranks are horizontal, the large when they are vertical.
so, apparently non-biopace ellipticals are bad for the knees, but biopace isn't.
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Old 07-07-04, 01:34 PM   #11
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Quote:
Originally Posted by [165]
were the rumors of biopace trashing knees bunnk then? I heard too many of these types of rumors
The same things are said about singlespeeds and fixies
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Old 07-07-04, 01:44 PM   #12
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I have to agree with you, I think they are not a problem. I looked at mine and the elipse is longer at the cranks and shorter 90 degrees from the crank. So when you're vertical there is actually less strain than when you're horizontal.
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Old 07-07-04, 02:13 PM   #13
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Quote:
Originally Posted by Raiyn
The same things are said about siglespeeds and fixies
I was asking a question, yet you state fact. Where's the proof you have?
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Old 07-07-04, 02:16 PM   #14
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Quote:
Originally Posted by [165]
I was asking a question, yet you state fact. Where's the proof you have?
Look Sparky. I was pointing out a fact that people say a lot of things - doesn't necessarily make them true. Get all defensive and crap.
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Old 07-07-04, 02:22 PM   #15
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Wow...you need real friends
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Old 07-07-04, 02:28 PM   #16
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Quote:
Originally Posted by [165]
Wow...you need real friends
You need to not bang people for "proof" when they make a simple statment.
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Old 07-07-04, 02:31 PM   #17
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once again...you and your assumptions. All paranoia and no Prozac make Raiyn crazy. Now, go take your nap. Troll elsewhere
Done
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Old 07-07-04, 02:34 PM   #18
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STOP IT GUYS!

You're scaring kitty!


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Old 07-07-04, 02:35 PM   #19
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My assumptions?
Quote:
Originally Posted by [165]
I was asking a question, yet you state fact. Where's the proof you have?
You have a lot of nerve calling me a troll when you started this BS
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Old 07-07-04, 02:45 PM   #20
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Guys, take it easy.... drop back on the insults.

Thanks,

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Old 07-08-04, 12:34 AM   #21
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Is not "biopace" those oval-shape rings? Why would somebody try such a thing? Chain would go taught and then slack twice every rotation. You would not ride on oval-shape tires, would you? Why oval ring then?
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Old 07-11-04, 06:29 PM   #22
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I decided to run the stock biopace 48 when I converted my old hardtail to SS- until I figure out what I really want on it. Cynikal helped me build it up and as posted earlier by him, I have problems with high rpms. Reseaching the issue, normal biopace was designed for use under 90 rpm, a seperate model was designed for higher rpm pro's. At the higher rpms you really start to bounce due to the patterned resisitance in the cranks. It works but be forwarned. As for the additional power stroke, only felt it a couple times on slow rpm climbs, the resistance lessens as the pedal passes the 10/2 o'clock- or it could have been my imagination.

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Old 07-27-05, 12:38 PM   #23
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I ran my 1983 Trek as a "single speed" using the BioPace chain rings for a week or so, and then switched to a round ring. The round ring works much better. There is no chain tension device on my bike, so the position of the rear wheel controls chain tension. Although pressure on the pedal pulls the chain tight between the chainwheel and the rear cog, the tension was not consistent. At one part of the crank revolution, the chain was almost too tight, and on other parts it was too slack, and would sometimes fall off the chainring.

So, switching to an oval ring permitted a more consistent chain tension, and eliminated the chain coming off the chain ring.

As far as FEEL: I could not feel any performance difference. Nor have I ever felt a difference on my road bikes that have BioPace type rings.
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Old 07-27-05, 01:53 PM   #24
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Quote:
Originally Posted by Pessi
Is not "biopace" those oval-shape rings? Why would somebody try such a thing? Chain would go taught and then slack twice every rotation. You would not ride on oval-shape tires, would you? Why oval ring then?
If the oval is properly shaped then the chain would stay at nearly the same tension regardless of crank position (which is how biopace are shaped). When the oval is positioned so the longer "radius" is horizontal, the chain is "stretched" out further (if you measured from the end of the chain on the cog to the end of the chain on the biopace ring) than when the longer radius is vertical. However, when horizontal the chain is also not spread out as much vertically. Properly shaped, the function between the vertical and horizontal spread of the chain should be even.

And yes, this explaination sucked, I really need pictures.
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