OK to mix BioPace and non-Biopace chainrings?
06-22-22, 12:42 PM
#1
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OK to mix BioPace and non-Biopace chainrings?
I'm pretty sure the answer is, "It's OK," but since my other thread continuation didn't draw attention, thought I'd ask another quick question in my quest to be able to climb mountains and not blow up on the Ironman.
I've not had any luck finding a 130 BCD 38T Biopace; I can find a 40, but not sure that will help as much as I'd like. I mean, I know it will help, but I'd like to go straight to a 38t. I have swapped out the freewheel for a 14-28 (from a 13-23) (still a 6-speed).
I can get a 38t 130 BCD chainring here. I suppose I could just switch out both chainrings to make it consistent, but there's no real issue in using one Biopace and one regular ring, right?
The bigger question for me, since I'm not real familiar with new setups, is if it will be a problem to use what's billed as a 9/10 speed chain ring. I know cogs are much narrower the more you have, but is the same true for chain rings? Will a 6-speed chain present any issues?
Thanks in advance!
I've not had any luck finding a 130 BCD 38T Biopace; I can find a 40, but not sure that will help as much as I'd like. I mean, I know it will help, but I'd like to go straight to a 38t. I have swapped out the freewheel for a 14-28 (from a 13-23) (still a 6-speed).
I can get a 38t 130 BCD chainring here. I suppose I could just switch out both chainrings to make it consistent, but there's no real issue in using one Biopace and one regular ring, right?
The bigger question for me, since I'm not real familiar with new setups, is if it will be a problem to use what's billed as a 9/10 speed chain ring. I know cogs are much narrower the more you have, but is the same true for chain rings? Will a 6-speed chain present any issues?
Thanks in advance!
06-22-22, 02:36 PM
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My mountain bike came with a 48 (round) - 38 (Biopace) - 28 (round) chainring set. The combination shifted fine, but I am not a Biopace fan, and I obtained better ratio progression with 48-40-28, anyway. (I like an 8-tooth drop up front with a 2-tooth progression in back for a 1.5-step setup.)
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Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069
06-22-22, 02:40 PM
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06-22-22, 03:16 PM
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Two things to consider first.
A "big" (outer) Biopace ring will always be a relatively round one with only 3-1/2% variation of it's outer radius, while Biopace middle and inner rings will be either 8% variation or 3-1/2% variation (for the later HP, II or SG variants).
As such, using a round inner ring with the 3-1/2% outer ring will never be very noticeable.
A round 130mm chainring can be as small as 38t, but an early 130mm BioPace inner ring can only be as small as 42t, due to the out of roundness.
The later (HP, II and SG) 130mm variants can be as small as 40t, but are seemingly less common to find (other than in steel).
I've done almost all of my Road, MTB and CX racing over the past twenty five years on the same bike, using a couple of 110mm BioPace triples using 26/38/50t ring sizes, and found no issues with it during that time and to this day. It doesn't shift as quick as a modern, matched set of rings, and my smallest (26t) ring is there mostly so that a dislodged chain has a GOOD place to fall during a fierce CX race (I have several times overtaken rivals who dropped their chain during a race, but have had to stop for a chain drop perhaps only three times myself during all of those years (a fourth "broken chain" incident on Mount Diablo's final "wall" climb not counted).
Here I'm racing on the infamous BioPace chainrings this past December:
Oh, and I found this related link just the other day, from all those years ago back in 2004!
https://www.roadbikereview.com/threa...3/#post-154411
...Made the local sports headlines the same day:
https://live.staticflickr.com/7197/6...c70ae142_c.jpg
A "big" (outer) Biopace ring will always be a relatively round one with only 3-1/2% variation of it's outer radius, while Biopace middle and inner rings will be either 8% variation or 3-1/2% variation (for the later HP, II or SG variants).
As such, using a round inner ring with the 3-1/2% outer ring will never be very noticeable.
A round 130mm chainring can be as small as 38t, but an early 130mm BioPace inner ring can only be as small as 42t, due to the out of roundness.
The later (HP, II and SG) 130mm variants can be as small as 40t, but are seemingly less common to find (other than in steel).
I've done almost all of my Road, MTB and CX racing over the past twenty five years on the same bike, using a couple of 110mm BioPace triples using 26/38/50t ring sizes, and found no issues with it during that time and to this day. It doesn't shift as quick as a modern, matched set of rings, and my smallest (26t) ring is there mostly so that a dislodged chain has a GOOD place to fall during a fierce CX race (I have several times overtaken rivals who dropped their chain during a race, but have had to stop for a chain drop perhaps only three times myself during all of those years (a fourth "broken chain" incident on Mount Diablo's final "wall" climb not counted).
Here I'm racing on the infamous BioPace chainrings this past December:
Oh, and I found this related link just the other day, from all those years ago back in 2004!
https://www.roadbikereview.com/threa...3/#post-154411
...Made the local sports headlines the same day:
https://live.staticflickr.com/7197/6...c70ae142_c.jpg
Last edited by dddd; 06-22-22 at 03:27 PM.
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06-22-22, 03:35 PM
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Great info, folks, thanks. I thought I read here that I could find a 38t BioPace, but that they're hard to come by. Maybe impossible?!
In any case, off to order a 38t. Thanks again.
In any case, off to order a 38t. Thanks again.
06-22-22, 06:47 PM
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06-22-22, 07:07 PM
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06-22-22, 07:29 PM
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I mix BioPace and non-BioPace rings in the pile of spare rings in my garage. The biggest difference between them is that I might use the non-BioPace rings someday. 
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06-22-22, 10:23 PM
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06-23-22, 12:45 PM
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...I use one of the tiny Biopace rings as the interior ring on a triple, as a granny gear on a touring bike for steep hills with a load.
The BCD is whatever the smallest ones ran (94BCD maybe ??). It works very well for this, with a noticeable flat spot that increases my cadence.
Feels strange for a while, but then you get used to it.
...I use one of the tiny Biopace rings as the interior ring on a triple, as a granny gear on a touring bike for steep hills with a load.
The BCD is whatever the smallest ones ran (94BCD maybe ??). It works very well for this, with a noticeable flat spot that increases my cadence.
Feels strange for a while, but then you get used to it.
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