zukahn1 

This may seem off base but I got several nice steel Bio chain rings and would like to try them on my MTB . Would like to know if a bio small ring will work nice with regular mid/outer rings on a triple and what is the correct placement of a Bio inner ring does the tab or the labeling match up with the crank arm?

Piff 

If I remember correctly the little biopace symbol on the ring goes behind the crank. I dunno about mixing with regular rings, I've never tried.

thumpism 

The Biopace-ness is more exaggerated the smaller the ring is, so shifting from a BP granny to a round middle ring might be noticeable but you'd probably become accustomed to it.

canklecat

Mixing with regular round rings can result in finicky front shifting. I tried both for awhile -- 50 round big ring, Biopace 42T small ring, and vice versa, 52 Biopace, 39T round -- and soon switched back to both Biopace 52/42. Seemed to work better. I switched from 13-25 to 13-28 freewheel to give my legs a granny gear when the 24 or 25 cogs weren't enough.

I forget the factory orientation (that crank is in a box somewhere while I overhaul the entire bike), but there are lots of photos online. Users can change the orientation. For awhile I tried shifting one ring, then the other, then both, one notch from the factory default. It offered some advantages (more leverage on slow cadence climbs, but herky jerky feeling at faster cadence) and disadvantages in how it felt subjectively. But eventually I returned to the default position.

Miele Man

See here:

https://www.sheldonbrown.com/biopace.html

Cheers

zukahn1 

Thanks I will probably try using the bio peace for just the small ring on the triple were the shifting isn't as critical and a slight advantage will help on slow climbs.

dddd

It might be useful to know that several versions of Biopace featured rounder (3.5% variation vs. 8% variation) middle and small rings.
These were BioPace II, HP and SG.

Note that all BioPace cranksets featured the rounder shape on the big ring.
Also, that the rounder ones can have a smaller tooth count for a given BCD size: 40t vs. 42t on a 130BCD crank, and 36t vs. 38t on a 110BCD crank.

I've done almost all of my racing over the years on BioPace HP rings and find them to my liking.

dddd

The article at Sheldonbrown.com mentioned that "...The triathlete benefits because the motion is a little bit closer to that of running, making the transition easier."

I found this interesting as most of my racing success was in Cyclocross. I thought the Biopace was effective for starting line sprinting (using a full-power short-shifting technique) and for sprinting back up to speed after a technical section of the course found me in too tall of a gear.

Reynolds 531 

FYI, the Biopace ring can be rotated CCW 72 degrees (one hole), and will EXACTLY match the "modern" clocking / ovality of Q-ring, AbsoluteBlack, SRAM etc.

Lascauxcaveman 

I noticed this on my Cannondale when I got it. Its small ring had the extreme (8%) Bio-shape and the middle and big ring were plain round rings. The small-to-middle shifting was pretty weird, so I just got a round small ring and was much happier. I didn't like how lumpy that little ring felt, even though I don't mind BioPace (the lesser variety) on another bike I have.

zukahn1 

On the one hole rotation is this forward o backwards.

zukahn1 

As a follow up I put the bio peace small ring on my Hardrock it's one of the 90's 2nd gen steel SG rings with the lesser oval. It works great took test ride about 20 miles tarmac and off road up and down hill using the small ring about half the time no issues the up shift small it middle varies a bit but it's fine with the friction Suntour thumb and FD actually a bit better than the round ring turn out the steel bio seems to grab get the chain a bit better quicker on uphill shifts. Other than a very slight improvement in climbing on steep climbs I don't noitice much difference.

dddd

I'm surprised that this might be the first time I've heard anyone mention how much better that steel chainring teeth grab the chain.

It's one of the things that I really like about old Schwinn doubles, bikes with old cotter cranks, even cheap, 1990's MTB's.

Miele Man

The original post stated:
"Originally Posted by Reynolds 531 View Post
FYI, the Biopace ring can be rotated CCW 72 degrees (one hole), and will EXACTLY match the "modern" clocking / ovality of Q-ring, AbsoluteBlack, SRAM etc."

CCW = Counter Clock-Wise

Cheers

3Roch

the tab lines up with (goes behind) the crank arm

Reynolds 531 

.

icemilkcoffee 

On the subject of retrofiting biopace chain rings, I put some Bio-Pace SG chainrings from the Exage M500 group onto my RSX crank. Lo and behold the mid and big rings were visibly closer together than the mid and small rings. It turns out Shimano uses washers to space out the middle chain ring:
https://si.shimano.com/pdfs/ev/EV-FC-M500-1102.pdf
Why Shimano why?
Good thing for me the Ebay seller included washers with the chain rings and bolts.

John E

For me, the best location for a BioPace ring is in the giveaway box I sometimes put out at the end of the driveway. I bought the Schwinn with a 48-38-28 ringset, in which the middle was a Biopace, and one of the first changes I made was to replace it with a 40T round, not only for a better gear ratio progression, but also because I hated the BioPace.

top506

Steel rings?

Top

icemilkcoffee 

Alloy rings

dddd

The washers are used with more-equally spaced gear ratios, which helps the chain shift up to the middle ring with more authority (for any given cage movement distance) without catching the big ring's teeth.

When half-step rings are used, you leave the washers out. This gives good shifting down from the big ring without chain skating between the larger rings, and improved shifting down from the middle ring for any given amount of cage movement in that direction. Remember that the middle ring is further from the cage so getting the chain to catch on it when shifting up requires more sideways movement to angle the chain sharply enough across the plane of the middle ring.

At some point when half-step ring options on complete cranksets were finally a thing of the past, Shimano started spacing the rings evenly without the use of any middle-ring spacers.
XTR M900 ca. 1991 might have been the first such crankset, but I'm just taking a guess about that.

repechage

that was the hot set up in 1987-88.

zukahn1 

Well this is setup is on a 88/89 bike with 4500 Suntour accushift 6/7 Thumbies which seem to shift anything 6/7 nicely and the front is last generation power type friction accushift .

stardognine

This is a great thread, lots of good info. 👌

It confirms what I’ve been learning, slow but sure, about just a bio space granny, with rounded for middle & large. Also, I had the more radical bio space rings, might be better off with the tamer one. 🤔

I’ve never really had a good Accushift setup (yet), but lovin’ my power thumbies (ratchety friction). I might try some XT 7-speed thumbies soonish, I have them, might as well try them. I thought about the possibility of leaving the left Power thumbies on, for the front derailleur, so trimming is better, if needed. Then just try the indexed righty Shimano. 🤔😎

stardognine

So it’ll be appropriate for my ‘86 High Sierra. 😁