44T for my middle ring (110BCD) on my touring bike, would you like a picture?

Mine was a fairly useless 28-46-50. I swapped the smaller rings for a plain 26-40- and left the Biopace 50. Shift reasonably well. Not great I guess as you have to overshift a bit going from the granny to the middle ring but that might be half-step front derailleur it's got. Come to think of it I'd like to pickup a Biopace in the 38-40 range just so it matches the big ring. How small did they go for the little ring? Was there a 24? Ideally I'd like to go 24-40-50 or thereabouts.

My wife and I both have had road and mountain bikes with Biopace chainrings. I never saw or felt anything bad about them, such as detractors have written about. They worked fine and shifted fine. Unfortunately, I do not have any spare chainrings, but it looks like there are plenty above available.

I can't feel the difference while pedaling, but after a long ride on round rings my knees hurt. Not so with Biopace.
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Hey Everyone,

I have a 52/42 Shimano Biopace chain ring. Is it possible to replace the 42T chain ring with a 38T chain ring? Appreciate your comments.

The smallest 130 BCD ring was/is 40 t.

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If (as I assume) you're talking about a road crank with 130 mm bcd rings, then no, the smallest ring you can get is 39t; and it will be a round one, not biopace. If the rings are 110 bcd, then yes, no problem.

38T round rings are available for 130 BCD. Rare but there.

Woah, it's like an auction. Do I hear 37t? Going once... going twice...

Smallest 130 BCD BioPace rings were 40T and steel-only, I believe. I searched once, and they were hard to come by. I think Shimano was hedging their bets on the replacement market, so that's why they made some of them in steel. I have a 48/38/28 (110/74) BioPace set, all steel. They're presently making sure my tool shelf doesn't float away. :lol:

Regular 38T rings aren't that hard to come by in 130 BCD, and might not shift too badly with a 52T BioPace ring, although not as well as mated rings: 130 mm BCD Road Bicycle Chainrings (Chainwheels) from Harris Cyclery

I have one of the Sugino 38s on my rando bike, and it does the job perfectly:
http://i36.photobucket.com/albums/e2...mmuter/38t.jpg

I think I have a nos small ring willin to trade it. No dumpster here just help lol

I have sugino bio also does that work with your set up?

want to buy 38T 110 mm BCD for working Lotus Odyssey
 

I know this is a very old thread, but it seems to have a lot of folks with old Biopace chainrings, and I couldn't find my size & style on eBay.
I have a circa 1987 Lotus Odyssey with a Biopace triple chainset. They look like aluminum, but I'm no expert. The middle chainwheel, 38T, 5 bolts, 110 mm BCD, has worn teeth from decades of mis-shifting, and the chain slips when I pedal hard. So I'm looking to buy a replacement. This is to use, not to collect dust, so the teeth need to be in good shape.

Do you have a fridge (or other) magnet?

I think I know the style of chainring you're referring to. I just swapped a set of silver steel biopace rings from one crank arm to another, and yeah, it was hard to tell visually that they were steel. They weren't even that much heavier than aluminum rings. I resorted to using a magnet just to confirm.

I took that crap crank off my High Sierra. It's around somewhere, or should I say; a-oval?

Ah, a magnet, of course!
I tested; my chainrings are aluminum. I actually don't care which metal, unless there's some bad metal reaction with mixing them.

The other companies made oval rings as well. Check Ebay for SR Sakae OvalTech rings.

The best thing I ever did was take the oval rings off the crank and replace them with round. Shifting is noticeably quicker and I notice no difference in pedaling effort. This is on an '84 Pug.
Jon

Biopace chainrings are not oval. True, you could put ten of us in a room, and get twelve different opinions about biopace. But any experience with oval chainrings indicates nothing about biopace, or vice-versa.

^ True. I think @seypat meant to say that other companies got in on the "point-symmetric egg curve" chainring bandwagon, too. :lol:

Yeeaahhh.....that's what I meant to say. Glad you had my back.

Here are the SR Sakae offerings on the Bay.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=SR+Sakae+ovaltech+chainrings&_sacat=0

Sugino's line is called Cycloid!

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=Sugino+Cycloid+chainrings&_sacat=0&LH_TitleDesc=0&_osacat=0 &_odkw=Sugino+oval+chainrings

Suntour 'powerings' xcd crankset. I just cleaned these up, and was surprised that the rings are fine to bolt back on in any orientation! The imprint is essentially the index, and these have the widest part about 30° past the crank arm.
https://cimg8.ibsrv.net/gimg/bikefor...9c30627cbf.jpg

Yes, cycloid! The two inner rings are cycloid, while big ring is round.

The Biopace is within the oval or ovoid family, which is loosely defined in geometry. It's closest to a shortened stadium or capsule subset of ovals. It's elongated, symmetrical, slightly blunted at the elongated lobes rather than egg or teardrop shaped. Without the reference point of a handy circle, Biopace rings at a glance appear round. But for all practical purposes it's an oval.

In practical application it's pretty subjective and depends on the user.

I've been trying a 52/42 alloy road bike Biopace double for several months on an older Trek 5900. Due to my less than ideal cadence I got some dead spots in the big ring, while the little ring felt pretty good. It never feels as smooth as the round rings in a 50/39 double on my other road bike. But I wondered about whether the elongated lobes might coincide with my primary downward power strokes.

I've experimented with repositioning the rings, then taking test rides on a very familiar training circuit I've ridden hundreds of times, a roller coaster type terrain with a mix of short, steep punchy climbs and a nearly mile long fairly steady gradual 2% climb. Helps reduce some variables due to wind and physical condition on any given day.

I get the best results with the little ring conventionally oriented and the big ring rotated clockwise 72 degrees (the fixed limits of the 5-bolt 130bcd crank). Rotating the 42T chainring to match the new position of the big ring created dead feeling spots in the little ring. No idea why the rings would feel different with the elongated lobes oriented differently. But it's consistently good for an additional 1 mph average over the same 20 mile circuit, primarily due to the slight felt advantage of the reoriented big ring. And this was during a test period when I'm far from my best conditioning (battling a month-long respiratory virus or inflammation, lots of days when I'm so congested I can barely breathe).

I've found an orientation that feels right with both rings so I'll continue to ride 'em like that for awhile. Subjectively it feels more efficient than a comparable circular 52/42 combo, even if the full cadence stroke feels less smooth. The Biopace also seems to work better slightly below my preferred 90 rpm cadence. If there's a real advantage it'll show over time in my data. At 61 I'm not getting faster or stronger, and my diet and fitness routine is already pretty good. So I doubt fitness will be a significant factor.

Well, some of us who posted on this thread are still around. Heck, it's only been 10 years- still a youngster for a zombie thread.

I bet that those boxes of take-off Biopace chainrings are still at Euro-Asia Imports. That won't be much help to you- Euro-Asia only sells to select bicycle shops and it would take some motivation for them to dig out those old Biopace chainrings.