Ken Cox

I've ridden with a Shimano Biopace chainring for over a year now.
So, yesterday and today I conducted an experiment.
I changed chainwheels several times durng the day, yesterday and today, in order to compare the Biopace with a conventional circular chainwheel.

I used a 53 tooth Biopace and a 52 tooth Sugino chainwheel, each with an 18 tooth EAI cog.
The 53 tooth Biopace chainwheel gave me 77.4 gear inches and the 52 tooth Sugino chainwheel gave me 75.9 gear inches; for a 1.5 gear inch spread.
I rode 13.7 miles in mixed urban and suburban traffic each time, for a total of four comparisons between the two types of chainwheels.

The 52 tooth Sugino ring should have felt a little easier to pedal, given a one tooth 1.5 gear inch advantage, but it didn't.
The Biopace ring felt much easier to pedal uphill, level, and downhill.
I could spin faster with the higher gear inch Biopace, brake more easily downhill, and climb much faster and easier.

For the 13.7 mile test circuit, uphill and downhill, stoplights and stopsigns, I averaged 17.5 miles per hour (46 minutes for each of two circuits) with the Sugino chainwheel and 20.4 miles per hour (41 minutes for each of two circuits) with the Biopace.

The Sugino chainwheel felt a little tighter and more precise, and made zero (I mean zero) noise.
The Biopace felt mildly vague compared to the Sugino, and, when next to a wall that reflected sound well, made a tiny amount of chain noise twice per spin as the chain "climbed" the Biopace ramp.

I adjusted the chain with the Sugino chainwheel so that it had about 1/8 inch play; and adjusted the Biopace chainwheel so that it had 1/8" to 5/8" play.
I could not feel the 5/8" play of the Biopace in the pedals; and, however, the Sugino felt wonderfully immediate, but only in comparison to the Biopace.

After the test I put the Biopace back on and intend to leave it that way.
I think I'll buy another Biopace from Harriscyclery and hang it on a nail in the garage for when I wear out my current Biopace.

The Biopace 77" ring/cog combo pedals as easily as a circular 72" ring/cog combo and goes as fast as a circular 81" ring/cog combo.
The bad news?
As far as I know, Biopace requires a 130mm BCD crank, which some folks find aesthetically and conceptually unacceptable.
I got some 130mm BCD Stronglight Track cranks from Bussinesscycles and people comment favorably on their appearance.

vomitron

You should do the test double-blind with test subjects on rollers. That's the real test right there.

travsi

+1

dutret

Did you use an HRM? It seems like without that the difference is pretty much subjective no matter how exact the conditions.

I hated biospace though and I gave it more then a fair try. That was on geared bikes however so I can picture how it could be different on a fg. Having to force your way up hills at really low cadence and not having to push though the dead spot with varying resistance might ampplify the benefit and nullify the main drawback.

Incidentally doesn't this nullify peoples main reason for riding fg since it lessens the "feel" of pedaling? If you really want efficiency shouldn't you jsut get a freewheel?

iamtim

I roll Biopace on my fixie as well; I, too, get a little chain noise as it "climbs the gear" and a wee little slop as it goes back down, but nothing that would dissuade me from rolling Biopace. I can certainly feel a difference climbing with Biopace as opposed to climbing without.

Re-Cycle

Nope, remember that the whole point of the biopace is a constantly changing gear ratio so... just cause you entered the BP chainring in to a gear calculator and ti spat out '77.4' dosn't mean anything. That calculator assums you are using round chainrings.

dutret

While the ratio is constantly changing the gear inches will be the same no matter how the ring is shaped since gear inches are defined by a single revolution of the ring. The average ratio will also be the same as it would for any other 77.4" set up. Comparing this average value is not completely devoid of meaning either.

jfmckenna

I don't think anyone will notice a difference between a 52 and a 53 easily. I do notice the wierdness of Biopace when I ride my brothers bike though.

Aeroplane

I'm still keeping my eyes open for a cheap biopace ring. Thanks for your study, Ken.

iamtim

What size are you looking for? While I'm loathe to let go of Biopace rings because I like them and they are hard to find, I've got a 52 sitting around that I'll probably never use; you're welcome to it.

Re-Cycle

Good thing no one around here has figured out the crazy ninja powers of BP chainrings, I use one on the shop sign and no one has lifted it [yet].

space_robots

It will probably be gone by tomorrow.

Matthew A Brown

People, ebay. No one gives a **** about Biopace. I got a 600 crankset with Biopace rings for like, twenty something dollars. Cheap.


Biopace = awesome. Doesn't play well with brakeless, though, what with the variable tensions n'stuff.

space_robots

this site claims that the "general consensus is to (if you are buying a new bike) get the
dealer to change the chainrings to round ones."

https://www.faqs.org/faqs/bicycles-fa...section-7.html

But who the hell is faqs.org anyway?

iamtim

[QUOTE=Matthew A Brown]I got a 600 crankset with Biopace rings for like, twenty something dollars.[QUOTE]

That's how I got mine; if you buy them on a crankset you can get them cheap. But last time I checked, individual Biopace rings were hitting between $20 and $40 on eBay.

Doesn't make sense. I guess I'll just wind up with a large collection of Shimano 600 cranks when I need more chainrings.

The LT

I also have a biopace chainring(52t i think) that I would give away....and as others have said I got mine with a set of shimano 600 cranks....if anyone wants it PM me