Are Bio-pace or similat chainrings advantageous for touring?

On Dec 3, 12:23 pm, Sir Ridesalot wrote:
As an aside to something on another thread I mentioned Bio-Pace
chainrings. Are these or similar shaped chainrings of any advantage to
a casual or touring cyclist on a road bike?


I had Biopace rings on my '89 Miyata:

http://i53.tinypic.com/2n83cpy.jpg

.... and have them on my Nishiki Pueblo:

http://i53.tinypic.com/jihxk0.jpg

I have ridden a lot of bikes in my day, am hard pressed to tell much
difference. I guess I can sort of feel the effect if I think about it
as I ride, but my legs and nerves and everything seem to adjust
dynamically to whatever force is needed moment to moment to turn the
cranks around and around.

On 12/3/2011 7:35 PM, DirtRoadie wrote:
On Dec 3, 4:34 pm, wrote:
On 12/3/2011 3:19 PM, wrote:


......

Below is a diagram I made once by tracing photos of each variety I could
find photos of online, at the time. Note that the long-axis are not all
aligned, nor are they drawn to scale--this was just to demonstrate the
different shapes.http://www.norcom2000.com/users/dcim...ies/recumbent/...

That's a useful comparison of _shape_ but completely fails to take
into account the _orientation_. Aside from a somewhat different shape,
the primary distinguishing characteristic of BioPace rings was the
seemingly inverted relation between crank orientation and effective
chanring diameter. Most ovalized rings put the major axis of the oval
about 90 degrees from the crankarms. BioPace rings put those two
elements almost in line.
.....

Just to compare shapes, this diagram was easiest. When I made it, at
least one brand wasn't available for a 5-bolt crankarm, and by the time
I made this diagram at least 3 brands were out of production anyway. To
a degree it was rather academic even back then.

This diagram spring out of a discussion that "BioPace rings would ruin
your knees". When I started comparing side-photos of the few different
rings I could find, the BioPace was the one closest to round that there
was.... and yet these allegations of "knee-wrecking" didn't appear to
occur with the other rings. The orientation could have influenced that,
but then again, the diameter variance in a typical big BioPace ring was
rather small, no matter where it was oriented.

I would find it difficult to believe that there would be huge efficiency
gains in using a non-round chainring, at least one that would function
with a normal double- or triple-chainring bicycle drivetrain. I see it
as an improvement in comfort rather than performance.

About the worst thing that it will likely cause is poorer shifting.

raamman wrote:

no, in my opinion, you have an uneven resistance to the pedal which
likely will not match a riders specific musculoskeletal system; you
then have an imbalance right where force is applied the most- an
although a human body is infitely adaptable- I fail to see how such
can provide a positive response

Human legs can't apply the same amount of force at different crank
angles, which is exactly why you might want differing mechanical
advantage at different angles.

I use a 38t Sakae Oval Tech chainring (similar in eccentricity to
first generation Biopace) on one of my regular bikes; all my other
bikes have round rings. I can tell the difference in feel, but I
think that at moderate cadences, orienting the ring to pull more chain
during the leg's downstroke makes sense, and feels right. At high
cadences, the accelerations in the crank's rotation make the pedal
stroke feel jerky compared to round rings.

I don't have a strong opinion one way or the other about Biopace's
different orientation. When I used a Biopace triple crank in the
past, I eventually settled on Biopace orientation for the middle and
large rings, with traditional elliptical orientation for the granny
ring (which I only used for slow grinding climbs).

Chalo

On Dec 4, 12:17*pm, DougC wrote:
On 12/3/2011 7:35 PM, DirtRoadie wrote:





On Dec 3, 4:34 pm, *wrote:
On 12/3/2011 3:19 PM, wrote:

*......

Below is a diagram I made once by tracing photos of each variety I could
find photos of online, at the time. Note that the long-axis are not all
aligned, nor are they drawn to scale--this was just to demonstrate the
different shapes.http://www.norcom2000.com/users/dcim...ies/recumbent/...

That's *a useful *comparison of _shape_ but completely fails to take
into account the _orientation_. Aside from a somewhat different shape,
the primary distinguishing characteristic of BioPace rings was the
seemingly inverted relation between crank orientation and effective
chanring diameter. Most ovalized rings put the major axis of the oval
about 90 degrees from the crankarms. BioPace rings put those two
elements almost in line.
.....

Just to compare shapes, this diagram was easiest. When I made it, at
least one brand wasn't available for a 5-bolt crankarm, and by the time
I made this diagram at least 3 brands were out of production anyway. To
a degree it was rather academic even back then.

This diagram spring out of a discussion that "BioPace rings would ruin
your knees". When I started comparing side-photos of the few different
rings I could find, the BioPace was the one closest to round that there
was.... and yet these allegations of "knee-wrecking" didn't appear to
occur with the other rings. The orientation could have influenced that,
but then again, the diameter variance in a typical big BioPace ring was
rather small, no matter where it was oriented.

This is much less true on the smaller Biopace rings. I measure a 26t
(74 mm bolt pattern) BP ring at ~98mm to tooth tips on the major axis
and ~82mm on the minor axis. That would be roughly the equivalent of a
variation between 24T (smallest that fits 74mm pattern) and 29T.

I would find it difficult to believe that there would be huge efficiency
gains in using a non-round chainring, at least one that would function
with a normal double- or triple-chainring bicycle drivetrain. I see it
as an improvement in comfort rather than performance.

With a rider being part of the equation those two elements are not
mutually exclusive and there is likely some correlation.

About the worst thing that it will likely cause is poorer shifting.

And, in fact, BETTER shifting is a possibility.

DR

DirtRoadie wrote:

DougC wrote:

[...] the diameter variance in a typical big BioPace ring was
rather small, no matter where it was oriented.

This is much less true on the smaller Biopace rings. I measure a 26t
(74 mm *bolt pattern) BP ring at ~98mm to tooth tips on the major axis
and ~82mm on the minor axis. That would be roughly the equivalent of a
variation between 24T (smallest that fits 74mm pattern) and 29T.

26t was a Biopace HP model, which was rounder than the 28t version
that preceded it. The 28t ring also approached the minimum radius
possible on a 74mm bolt pattern, which is to say about the same as a
24t round ring. That means that its largest radius must have been
equivalent to at least a 31t ring, if not larger.

Chalo

On Dec 4, 10:45*pm, Chalo wrote:
DirtRoadie wrote:

DougC wrote:

[...] the diameter variance in a typical big BioPace ring was
rather small, no matter where it was oriented.

This is much less true on the smaller Biopace rings. I measure a 26t
(74 mm *bolt pattern) BP ring at ~98mm to tooth tips on the major axis
and ~82mm on the minor axis. That would be roughly the equivalent of a
variation between 24T (smallest that fits 74mm pattern) and 29T.

26t was a Biopace HP model, which was rounder than the 28t version
that preceded it. *The 28t ring also approached the minimum radius
possible on a 74mm bolt pattern, which is to say about the same as a
24t round ring. *That means that its largest radius must have been
equivalent to at least a 31t ring, if not larger.

I don't know the model designations nor dates of origin but my old
parts repository contained a 28T steel BP ring and the aforementioned
aluminum 26T. I don't believe the 26T is an "HP" version.

The major axis is nearly identical between the two, while it is the
26T which has a minor axis that matches a 24T (~81mm) as you describe.
The 28T is noticeably more round/oval (100/92mm) while the 26T at
98/82mm is also almost angular in appearance, somewhat like a
parallelogram with rounded corners.

The overall roundness of the 28T ring counters my prior generalization
that smaller BP rings are less round.

There are obviously several flavors of BioPace.
DR

On Dec 3, 2:23*pm, Sir Ridesalot wrote:
As an aside to something on another thread I mentioned Bio-Pace
chainrings. Are these or similar shaped chainrings of any advantage to
a casual or touring cyclist on a road bike?

I found them a little smoother at lower cadences--but that could also
be a placebo effect. As others have stated--the shape wasn't so
radical that you likely wouldn't get used to the feel in a couple
miles. If I needed a triple square taper crankset for a utility/mtb/
tour bike, and I found a set in the discard bucket with the correct
chain rings, I'd not hesitate to use it.

On Dec 5, 4:42*pm, DirtRoadie wrote:
On Dec 4, 10:45*pm, Chalo wrote:









DirtRoadie wrote:

DougC wrote:

[...] the diameter variance in a typical big BioPace ring was
rather small, no matter where it was oriented.

This is much less true on the smaller Biopace rings. I measure a 26t
(74 mm *bolt pattern) BP ring at ~98mm to tooth tips on the major axis
and ~82mm on the minor axis. That would be roughly the equivalent of a
variation between 24T (smallest that fits 74mm pattern) and 29T.

26t was a Biopace HP model, which was rounder than the 28t version
that preceded it. *The 28t ring also approached the minimum radius
possible on a 74mm bolt pattern, which is to say about the same as a
24t round ring. *That means that its largest radius must have been
equivalent to at least a 31t ring, if not larger.

I don't know the model designations nor dates of origin but my old
parts repository contained a 28T steel BP ring and the aforementioned
aluminum 26T. I don't believe the 26T is an "HP" version.

The major axis is nearly identical between the two, while it is the
26T which has a minor axis that matches a 24T (~81mm) as you describe.
The 28T is noticeably more round/oval (100/92mm) while the 26T at
98/82mm is also almost angular in appearance, somewhat like a
parallelogram *with rounded corners.

The overall roundness of the 28T ring counters my prior generalization
that smaller BP rings are less round.

There are obviously several flavors of BioPace.
DR

Biopace, Biopace II, Return of Biopace, Biopace Strikes Sack, Revenge
of Biopace. Biopace in the 21st Century and Biopace, the Egyptian
Connection. :-)

When should I use Biopace?

On Dec 5, 6:01*pm, landotter wrote:
On Dec 3, 2:23*pm, Sir Ridesalot wrote:

As an aside to something on another thread I mentioned Bio-Pace
chainrings. Are these or similar shaped chainrings of any advantage to
a casual or touring cyclist on a road bike?

I found them a little smoother at lower cadences--but that could also
be a placebo effect. As others have stated--the shape wasn't so
radical that you likely wouldn't get used to the feel in a couple
miles. If I needed a triple square taper crankset for a utility/mtb/
tour bike, and I found a set in the discard bucket with the correct
chain rings, I'd not hesitate to use it.

When it's that cheap. Agreed.

DirtRoadie wrote:

I don't know the model designations nor dates of origin but my old
parts repository contained a 28T steel BP ring and the aforementioned
aluminum 26T. I don't believe the 26T is an "HP" version.

The major axis is nearly identical between the two, while it is the
26T which has a minor axis that matches a 24T (~81mm) as you describe.
The 28T is noticeably more round/oval (100/92mm) while the 26T at
98/82mm is also almost angular in appearance, somewhat like a
parallelogram *with rounded corners.

The overall roundness of the 28T ring counters my prior generalization
that smaller BP rings are less round.

There are obviously several flavors of BioPace.

I guess that's true, but up until now I had only distinguished the
original Biopace from Biopace HP, which was closer to round. The
original triples were 48-38-28 only, because the 28t and 38t rings
could not be made smaller at that shape and still fit on a 110/74mm
spider.

Chalo