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Old 07-25-07, 10:08 AM   #1
Terrapin Tim
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Shimano 105 Egg Shaped Chain Rings????

I just picked up a mid 90's Specialized Road bike with complete 105 components. As I started a clean up I found that the Chainrings were Oval Shaped... A quick call to Specialized confirmed that the egg shape was intentional and not a manufacturing defect......WTF ????

Is it posssible to remove these odball Chainrings and install current 9 spd chain rings or do I need to replace the entire Crank set ?????
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Old 07-25-07, 10:10 AM   #2
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It was called Biopace. Yes you can replace them with round chainrings.
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Old 07-25-07, 10:22 AM   #3
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"Bio-pace" as it was marketed by Shimano was another idea that had been around for, actually, a long time. Shimano packaged it up and slapped it on a crap load of bikes and off it went. (They did the same thing with index shifting, but that actually worked) Bio-pace was supposed to work to eliminate "dead spots" in your pedal stroke. Of course, pro's and other "high performance" riders would have nothing to do with it and if you couldn't afford Dura-Ace, you certainly put some money out for a pair of proper round chainrings (or a trio if you were a mountain biker). Then people started talking about people having knee problems from riding them. I don't if that was really true, but I seem to remember (and possibly incorrectly) that Andy Pruitt said they sucked, so...they sucked. Suntour did have a version of Bio-pace for their bikes, but I do not recollect what it's name was. It pretty much silently disappeared right around the time everything went to eight speed. So, there you have it in a nutshell.
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Old 07-25-07, 10:35 AM   #4
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Tim,

Don't just dump them. In recumbent circles, elliptical chain rings are the buzz and they bring in big bucks to the companies that sell them. I don't know how the Biopace rings compare, but you may find a buyer. If you don't want to do that, I have 105 rings (Triple) on a bike I'm not using. We could swap. My rings are 52, 42, and 30.

Tom Balmer

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Old 07-25-07, 10:48 AM   #5
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I think the equivalent SunTour part was called OvalTech. I remember wanting to drop the gearing on my SunTour Edge equipped bike, and I swapped out both rings for round 50/39's.

It's interesting sometimes how "fashionable" an item has to be for market acceptance.
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Old 07-25-07, 11:06 AM   #6
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My first mountain bike had biopace chainrings and I rode that thing exclusively for 15 years, including the '88 Ride the Rockies (460mi in 7 days). If there was anything wrong with the chainrings, I never noticed. I wouldn't change them out unless they are worn out.
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Old 07-25-07, 12:02 PM   #7
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Just ride the biopace set up. If you can actually feel a difference - and don't like it - then just install new chain rings. I predict you wont' bother with the expense.

My old Bianchi which I rode for about 10 years has biopace rings. I never noticed one bit of difference between them and the round rings I rode for 20 years before that, and now the round rings I've ridden on my current bike for the past 1000 miles this season. In fact, a couple of years ago, I had the inner biopace ring on the Bianchi replaced with a smaller ring (for gearing) and the new ring was/is round. Again, I could not feel any difference.

But I'd be curious to know what you think after you ride the bike a while.
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Old 07-25-07, 01:41 PM   #8
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Don't just dump them. In recumbent circles, elliptical chain rings are the buzz and they bring in big bucks to the companies that sell them. I don't know how the Biopace rings compare, but you may find a buyer.
Biopace is actually the most desirable, according to Sheldon. Un-worn examples fetch very good money on eBay.
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Old 07-25-07, 05:29 PM   #9
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The problem with them is that they are designed towards a "standard" knee. If you are outside of this standard, in any way, then it is possible that you could develop knee problems. That was the chief complaint against them that I remember.

I slapped a set on my bike, way back when, just to give them a try. I instantly hated them. I found I actually LOST power. They created a dead spot at the end of the downstroke and it felt like my power fell off sharply. I never did spend the time to actually figure out what was happening and, since they quickly and quietly disappeared, I never had to.

It really is the same for anything designed to an ergonomic standard. Fitness equipment was designed for a 5"10" 170lbs male user (that may have changed with the obesity epidemic in the west) and everything from office chairs, table heights, elevators to water fountains was designed to this (or some variation) standard. If you are outside of that standard then you may encounter difficulties. I'm sure there is no shortage of people on this forum who have had personal experience with this.
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Old 07-25-07, 06:11 PM   #10
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Biopace is actually the most desirable, according to Sheldon. Un-worn examples fetch very good money on eBay.
Really? The rings or the entire crankset with rings?
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Old 07-25-07, 06:25 PM   #11
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I have biopace on my commuter and it's fine. I'd save your money until they wear out (and mine have been going for 16-17 years or so now so that might be a while)
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Old 07-25-07, 06:59 PM   #12
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"Bio-pace" as it was marketed by Shimano was another idea that had been around for, actually, a long time...

... Bio-pace was supposed to work to eliminate "dead spots" in your pedal strok
I think you're confusing Biopace (no hyphen) with old-style elliptical chainrings. Biopace is the exact opposite of these, because they are oriented 90 degrees differently.

I like and use Biopace primarily because it is gentler on my knees, whatever Andy Pruitt thinks!

See: http://sheldonbrown.com/biopace

By the way, there's nothing "Biopace" about the cranks, it's just the chainrings. They used standard bolt circle patterns, 130 mm, 110 mm and 74 mm.

Currently I'm running a Biopace chainring on a SunTour crankset on my trike. Most of my bicycles also have Biopace rings.

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Old 07-25-07, 07:00 PM   #13
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Don't know if the Biopace rings kept me from having knee issues earlier or not, but they didn't seem to cause any.
I've found Biopace rings to greatly help my beat-up old knees, to the point of mounting them on all my bikes.
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Old 07-25-07, 07:13 PM   #14
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I used a Sugino Cycloid ring for a while. Can't remember if it was good, bad, or in-between.
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Old 07-25-07, 07:30 PM   #15
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I used to love Biopace, but I cannot use them as my MTB has four-bolt rings and my roadie is Campy 10.
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Old 07-25-07, 08:16 PM   #16
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I think you're confusing Biopace (no hyphen) with old-style elliptical chainrings. Biopace is the exact opposite of these, because they are oriented 90 degrees differently.

I like and use Biopace primarily because it is gentler on my knees, whatever Andy Pruitt thinks!

See: http://sheldonbrown.com/biopace

By the way, there's nothing "Biopace" about the cranks, it's just the chainrings. They used standard bolt circle patterns, 130 mm, 110 mm and 74 mm.

Currently I'm running a Biopace chainring on a SunTour crankset on my trike. Most of my bicycles also have Biopace rings.

Sheldon "I Like 'Em" Brown
Actually, your right, Biopace ( sp. ) are not truly oval. I'm sure you remember those waaaaaaaaaaaaaay elliptical rings from way back when. I only saw pictures of them but they were rather incredibly oval...lol. Your statement of fact that you still use them, like them and that they are easier on your knees is good testament that while they do suit some, they didn't work for others. I do not, however, believe that Biopace truly eliminates dead spots in the pedal stroke for the following reason. (Personally) I come from a racing background and have always thought that a proper pedal stroke should be something that is learned and once it is, efficiency will follow, and that goes for any style rider be it racing, touring, recumbent, or whatever. And that being said, once a proper pedal stroke is mastered, no amount of "non-roundness" will make an appreciable difference. If it really made a huge difference in performance, they most likely would still be in production (IMHO). As for knee health (as well as any other joint in the body), it's been my experience that a complete and proper fit of your body to the bike is the most important part of comfort, efficiency and proper bio-mechanics (yes that was a pun, and yes I meant it ). Anyhoo, that may be more like four cents, but hey...oh well.
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Old 07-25-07, 08:59 PM   #17
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Really? The rings or the entire crankset with rings?
Sets of rings seem to do best.
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Old 07-25-07, 10:33 PM   #18
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Actually, your right, Biopace ( sp. ) are not truly oval.
I remember a technical paper a Shimano engineer published called it a "Point-symmetric Egg Curve." I don't believe that is quite correct either, but the Shimano calls brake calipers "arches" so whadda they know, right? ;-)
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I do not, however, believe that Biopace truly eliminates dead spots in the pedal stroke...
Right. Read my article, "eliminating the [so called] dead spot" is not what they are about.

The "dead spot problem" is an imaginary problem. Actually, the big problem with the classical ellipticals (the opposite of Biopace) came from the fact that they were attempting to "cure" that "problem."

The result made your knees move super-fast just before suddenly changing direction at the top and bottom of the stroke.

Biopace is the opposite. Your feet (and knees) are moving fastest when the cranks are level, at the middle of the stroke. Then they gradually slow down so that at the vertical, upward/downward transition, your knees are moving slower than they would be with a round ring.

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Old 07-25-07, 10:41 PM   #19
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About half of my road bikes have biopace rings and half don't. When I'm pedaling, I can't tell which rings are round, and which aren't. I think the THEORY behind biopace is sound, it just doesn't offer enough improvement for me to notice.
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Old 07-26-07, 12:45 AM   #20
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I remember a technical paper a Shimano engineer published called it a "Point-symmetric Egg Curve." I don't believe that is quite correct either, but the Shimano calls brake calipers "arches" so whadda they know, right? ;-) Right. Read my article, "eliminating the [so called] dead spot" is not what they are about.

The "dead spot problem" is an imaginary problem. Actually, the big problem with the classical ellipticals (the opposite of Biopace) came from the fact that they were attempting to "cure" that "problem."


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I have to say that this is shaping up to be an interesting conversation. I find the dead spot topic to be the most stimulating. I would like to put another piece of info into this. There were actually two incarnations of biopace. The first had an "ovality" of 1.09 variation over a circular ring. This amount of variation actually increased load on the knee joint extensor muscles while decreasing load on the knee flexors, which is unfavorable as it pulls the knee to one side. It wasn't so much the dead spot Prof. Okajima (Shimano, 1983) was trying to eliminate, but to increase the efficiency of entire pedal stroke. The second (later) variation only had a 1.04 (compared to the 2005 "O'Symetric rings, which were 1.215) variation over a circular ring which was shown not to have a significant and/or measurable positive effect and behaved nearly identically in regards to power loads as a round ring. Also, it was also shown that eccentric rings, like biopace can only produce a favorable result under a specific type of condition, i.e. elliptical rings produce varying results when cadence, saddle position and terrain vary. However, your personal use testimony would contradict this finding in a real world application. Studies also found that elliptical rings tend to favor (strangely enough) riders with a higher percentage of lower to upper leg muscle mass. So, in conclusion I guess were back to where we started..it's really down to personal preference. Ciao!
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Old 07-26-07, 01:02 AM   #21
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I'm wondering if OP has "biopace" (or similar) rings or the more radical shaped oval rings you guys are talking about?
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Old 07-26-07, 01:05 AM   #22
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About the knee thing - I started riding again after a 16 year layoff and picked it back up on the old bike, one that had Biopace rings. Rode it for almost a year with no problems. Picked another bike to go on my first extended ride - this bike had round rings - and had knee problems about 54 miles out. Don't know if the Biopace rings kept me from having knee issues earlier or not, but they didn't seem to cause any.
Maybe I'm misunderstanding how much riding and/or adjusting you did on the second bike (which gave you knee pain). My first thought - based on my own experiences w/ Biopace and round - is that there might have been some other factor such as seat position, etc. I found that surprisingly small changes in seat positioning can cause me to have knee pain. 1/4 inch low can cause it for me, for instance.
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Old 07-26-07, 01:09 AM   #23
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Wasn't Bobby Julich using an elliptical chain ring set-up a few years ago?
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Old 07-26-07, 01:25 AM   #24
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I really like the Sakae OvalTech on my old Trek 930. It didn't originally come with it - I swapped over my chainrings from a broken 830 because it works so well. People who say they don't notice the difference in pedaling are probably referring to effort in higher gears. I can't believe that any rider in the lower gears would not notice a dramatic easing of pedal effort when going up a hill - especially with loaded panniers. There is a definite fall-away effect at the point of maximum exertion. No question about it, that's the whole idea. Perhaps some users relate this to "losing" power. I don't. I see it as a way to get the crank around the clock in the easiest, most efficient manner possible. Oh, yeah, it's good for the knees, too.
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Old 07-26-07, 07:31 AM   #25
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A friend of mine has Ovaltechs on her MTB, but it's too small for me to trial.

I'd like to try Biopace someday. redtires, is there a way to tell the difference between the two incarnations?
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