Shimano Shocker
03-05-19, 07:35 AM
#1
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Shimano Shocker
I finally wore out the front Main Sprocket ( I had taken the Small Sprocket off) on my 13 year old Schwinn Varsity. So I Mozied on down to the local Bike CoOp and picked up a Used Shimano Front Sprocket and. New Chain since the old original one was badly stretched.Put everything together and the Shimano Sprocket had a Hump in it when you Spun it. There were a Couple of Decent Bike Mechanics there and they could not figure it out. So I took a Screw Driver and Pried the Tabs up in the Low Spots then took a Scew Driver and put it in a Valley of the Sprocket in the High Spot and Whacked it. I mean Whacked it good. It seemed a little bit of the Hump came out but it was obviously still there. So went to riding it like it was and the New Chain started Skipping on the Free Wheel because the old Original Free Wheel was worn to the Badly Stretched old Original Chain. Went to an Old Fashion Bike Shop that fools with Schwinns to get a New Free Wheel, a Shimano Original Equipment Replacement for $14.99. You can't beat this Company. Then the Bike Mechanic looked down at the Front Shimano Sprocket and saw the Decal that said "Bio Pace." He said, Oh yeah, they made these back in the 80s and 90s with an Eliptical out of Round Shape to Theoretically help the Average Rider gain Momemtum in their Peddle Stroke. I said What? I was in total Shock.
The Owner came over, it is an Old Shop, and said Customers used to Bring their Bikes Back and say the Sprocket was out of Round. That other People Copied it but it never caught on and was phased out and Real Strong Elite Riders said it interfered with the Rythem in their Peddle Stroke. But he said they are still available on some Really High End Bikes for some Reason.
The Owner came over, it is an Old Shop, and said Customers used to Bring their Bikes Back and say the Sprocket was out of Round. That other People Copied it but it never caught on and was phased out and Real Strong Elite Riders said it interfered with the Rythem in their Peddle Stroke. But he said they are still available on some Really High End Bikes for some Reason.
03-05-19, 08:04 AM
#2
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If the "a Couple of Decent Bike Mechanics" didn't recognize that it was a Bio-Pace, they aren't decent bike mechanics.
03-05-19, 08:44 AM
#3
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Non-round chainrings have been around for more than a century. Most are simple ellipses, with the axis oriented in a manner to "improve" mechanical efficiency at a certain point in the pedal cycle. The degree of deviation from round and orientation of the axis depends on the "theory" behind the product.
In the late 1970s, Shimano went one better and invested a substantial amount of money into ergonomic and physiologic research to develop a non-round chainring that was not a simple ellipse, and actually varied shape depending on the tooth count. The smaller rings looked almost square, while the larger ones looked almost round. These came on the market with an expensive advertising campaign touting their performance benefits, and many bicycle manufacturers incorporated them into their products.
But they never caught on particularly well. Some people really liked them, a few really hated them, but most were completely indifferent. I'm surprised they have persisted on the market for as long as they have.
In the late 1970s, Shimano went one better and invested a substantial amount of money into ergonomic and physiologic research to develop a non-round chainring that was not a simple ellipse, and actually varied shape depending on the tooth count. The smaller rings looked almost square, while the larger ones looked almost round. These came on the market with an expensive advertising campaign touting their performance benefits, and many bicycle manufacturers incorporated them into their products.
But they never caught on particularly well. Some people really liked them, a few really hated them, but most were completely indifferent. I'm surprised they have persisted on the market for as long as they have.
03-05-19, 10:32 AM
#5
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JohnDThompson, given this Substantial Technical Investment by one of the Largest and Best Bicycle Accessary Manufacturers in the World, why didn't it catch on? Was it totally Ineffective?
I have found myself to be 2 mph faster...Just kidding.
I have found myself to be 2 mph faster...Just kidding.
03-05-19, 10:45 AM
#6
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Thread Starter
JohnDThompson, I forgot to ask you, given the out of round section of the Sprocket is supposed to create inertia, shouldn't that section be oriented a particular way to the Pedals and Cranks? But I do not see how this is possible because you have two Pedals and Cranks 180 degrees opposed. They can't both be oriented to the out of round section.
03-05-19, 11:05 AM
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Non-round chainrings have been around for more than a century. Most are simple ellipses, with the axis oriented in a manner to "improve" mechanical efficiency at a certain point in the pedal cycle. The degree of deviation from round and orientation of the axis depends on the "theory" behind the product.
In the late 1970s, Shimano went one better and invested a substantial amount of money into ergonomic and physiologic research to develop a non-round chainring that was not a simple ellipse, and actually varied shape depending on the tooth count. The smaller rings looked almost square, while the larger ones looked almost round. These came on the market with an expensive advertising campaign touting their performance benefits, and many bicycle manufacturers incorporated them into their products.
But they never caught on particularly well. Some people really liked them, a few really hated them, but most were completely indifferent. I'm surprised they have persisted on the market for as long as they have.
In the late 1970s, Shimano went one better and invested a substantial amount of money into ergonomic and physiologic research to develop a non-round chainring that was not a simple ellipse, and actually varied shape depending on the tooth count. The smaller rings looked almost square, while the larger ones looked almost round. These came on the market with an expensive advertising campaign touting their performance benefits, and many bicycle manufacturers incorporated them into their products.
But they never caught on particularly well. Some people really liked them, a few really hated them, but most were completely indifferent. I'm surprised they have persisted on the market for as long as they have.
As for their effectiveness, well they have won a few tours recently (not BioPace specifically, but the concept...):
03-05-19, 12:08 PM
#8
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03-05-19, 12:18 PM
#9
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Wow!
03-05-19, 12:54 PM
#10
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robertorolfo, well there is the evidence that Shaped Sprockets can be effective. Then why did they disappear from the General Market?
03-05-19, 03:42 PM
#11
Senior Member
From what I've read there are different school of thought on how to use the oval concept. Some believe that the oval should be used to increase the power (move more chain) during the power part of the stroke (3 o clock to 6/7 o clock). The other idea is to reduce resistance (move less chain) in the 3:00 to 6:00 and add momentum in this area to overcome the "dead" spot that occurs right after. The BioPace (late 1980's - early 1990's) was supposed to do the latter. Recall that Shimano mentioned that it was supposed to more closely resemble the biomechanics that were observed.
Shimano idea seems to make sense for those don't pedal in effective circles. This might have some benefit for a MTB when climbing since the resulting slower chain movement during the power part of the stroke would normalize the power to the wheel throughout the pedal cycle, less pulsing & slipping.
Just my personal thoughts from what I've read. Never tried any of these rings, not old nor new. Lots of differing opinions and studies have been done.
Shimano idea seems to make sense for those don't pedal in effective circles. This might have some benefit for a MTB when climbing since the resulting slower chain movement during the power part of the stroke would normalize the power to the wheel throughout the pedal cycle, less pulsing & slipping.
Just my personal thoughts from what I've read. Never tried any of these rings, not old nor new. Lots of differing opinions and studies have been done.
03-05-19, 03:51 PM
#12
Old Bike Craphound
I have bikes with Biopace, but most of my bikes have round chainrings. I do not think the difference is the most notable difference between bikes. Mostly I notice that it makes the front derailleur appear strange because it is closer to the teeth at certain parts of the stroke than others, but even that seems to work fine. One effect I have noticed is that Biopace chain rings seem to wear unequally and more quickly - they get a spot on the stroke where the chain skips and this seems to happen on Biopace bikes faster than my other bikes. Like so many of Shimano's "improvements" in the past few decades they seem to require that new parts must be purchased sooner than with the technology that preexisted the change. It almost makes you think that they are in the business of selling parts.
There are a number of people who believe that Biopace increases the risk of knee injuries, but I have not experienced any problem and have no view on this issue.
-Will
There are a number of people who believe that Biopace increases the risk of knee injuries, but I have not experienced any problem and have no view on this issue.
-Will
03-05-19, 04:10 PM
#13
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Biopace was 90° out of phase of what is now used.
Absolute Black are highly regarded.
Absolute Black are highly regarded.
03-05-19, 04:22 PM
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Bike Forums has finally found him, the last person on earth to be surprised. Who knows what other breathtaking revelations lie in his future? Wait til he learns about Air Lines. What tool will he use to repair it?
03-05-19, 05:25 PM
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I couldn't possibly explain the lack of commercial success. To be honest, I was pretty surprised when I found out that Froome was using oval rings, because I would have thought it would inspire countless people to give it a try. I mean, imagine if pre-scandal Lance was using something like that? Perhaps it's because Shimano aren't actually producing them, and they are his sponsor, so they seem intent on ignoring it (as shown in that video).
03-05-19, 05:50 PM
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Biopace failed because they didn't work.
They were designed 90° out of phase from where they should have been.
Modern ovals actually work because they are phased correctly. This includes Absolute Black, Rotor Q-Ring and the Osymetric rings used by Froome.
See post number 13.
-Tim-
They were designed 90° out of phase from where they should have been.
Modern ovals actually work because they are phased correctly. This includes Absolute Black, Rotor Q-Ring and the Osymetric rings used by Froome.
See post number 13.
-Tim-
03-05-19, 05:55 PM
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Look, I'm anything but a Shimano "guy," as I actually prefer Campagnolo, but I find it hard to believe that a company like Shimano would take all of that time and effort to create something that was completely wrong. Everyone has personal tastes and preferences, but I really don't see how you could declare it scientifically wrong if a bunch of competent engineers designed it, tested it and built it.
03-06-19, 12:27 AM
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It’s not wrong. It’s just a different idea.
03-06-19, 12:49 AM
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Originally Posted by Sheldon Brown
To a casual glance, Biopace chainwheels resemble elliptical chainwheels, but on closer examination they turn out to be the opposite of the classical elliptical design. The product of extensive research and computer-aided design, Biopace chainwheels have the small radius engaged when the cranks are horizontal, the large when they are vertical. This is because the Biopace design is based on a dynamic analysis of the motion and momentum of moving cranks and legs, unlike the static, geometric analysis that produced classical ellipticals.
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.
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.
03-06-19, 07:36 AM
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Look, I'm anything but a Shimano "guy," as I actually prefer Campagnolo, but I find it hard to believe that a company like Shimano would take all of that time and effort to create something that was completely wrong. Everyone has personal tastes and preferences, but I really don't see how you could declare it scientifically wrong if a bunch of competent engineers designed it, tested it and built it.
Lots of competent engineers design things that don't work. I make a healthy living off of fixing problems with engineered solutions.
-Tim-
03-06-19, 07:55 AM
#21
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There seem to be two different theories for Oval Shaped Front Sprockets or Chain Rings. The High Spot of the Oval in the Power Stroke, Shimano, and the High Spot of the Oval in the Transition, the New Modern Design. But no matter which one you have you can put the High Spot of the Oval anywhere you want by rotating the Chain Ring 90 Degrees at a time by mounting it on different Brackets on the Crank. So what is the difference?
If if you have two high spots in your oval,I understand that. But my Biopace seemed to have only one High Spot. That's what I did not understand.
If if you have two high spots in your oval,I understand that. But my Biopace seemed to have only one High Spot. That's what I did not understand.
03-06-19, 09:02 AM
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The oval chainring with only one high spot for made specially for one legged riders. Limited rings were made, you just happened to pick up the oddball one at the co-op.
03-06-19, 09:10 AM
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Since I kind of work in this area, I can testify emphatically that if you ask a computer the wrong question, it will get you the right answer to that wrong question very quickly. But its not the right answer to the right question!
03-06-19, 09:18 AM
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This specific issue reminds me of the Big Bang Theory joke. The physicist is asked "Why did the chicken cross the road?" After a bit of thought he answers "I have the answer, but it only applies to a perfectly spherical chicken in a vacuum".
To your point though, as I mention in another post, if the Biopace engineers sought to optimize leg acceleration, this may have been the wrong thing - solving for a spherical chicken. Thanks for the graphic you posted on the chainring orientation.
03-06-19, 09:31 AM
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It was my memory that Bio Pace was intended for Tri riders, to help the transition from the cycling leg motion to that of running. Something about changing the leg speed at it's different points within the pedal circle WRT the run swing. And since the good tri guys are pretty fast and racers will try stuff that has a promise of "free speed" Bio Pace rolled into the mainstream, all the way down the product line to recreational bikes soon enough. After all remember that Shimano has always been a company strongly driven by it's marketing ability.
I also remember reading of Shimano's claims of greater efficiency in applied power WRT Oxygen use. As road riding and MtB riding had somewhat different cadence and power flows the rings had different shapes, all designed to increase the leg's downward movement speed and slow it's speed over the top and through the bottom portions of the stroke but to different amounts between road and MtB set ups. Andy
I also remember reading of Shimano's claims of greater efficiency in applied power WRT Oxygen use. As road riding and MtB riding had somewhat different cadence and power flows the rings had different shapes, all designed to increase the leg's downward movement speed and slow it's speed over the top and through the bottom portions of the stroke but to different amounts between road and MtB set ups. Andy
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