Biopace chainrings

[123malford]

Does anyone have experience of Biopace chainrings in the 48-38-28 format when they were introduced to some touring bikes towards the end of the 80's. I was interested to know if they felt different to ride in comparison to standard rings rather than in any mechanical advantage they may or may not have conferred.

[foxyrider]

biopace - something akin to the antichrist!

I used biopace for a couple of years coz the bike had it fitted - boy was i glad to get rid when it wore out!

[sirmy]

My Muddy Fox Courier Comp came fitted with a biopace chainset, oddly with 28 - 38 - 48 rings (probably the standard at the time). I used it until the teeth on the middle ring became too rounded. I still have it in the hope of beng able to get new rings for it one day.

The rings appeared to come into their own when climbing, it certainly felt easier than with round rings. On the flat I wouldn't say they were any different to round rings. IIRC they were supposed to remove a dead spot in the pedal cycle and apply power more evenly through out the stroke.

Pity Shimano don't appear to have allowed any independent manufacturer to have produced replacement rings

[Gearoidmuar]

I had them on a mountainbike and on a racing bike. I liked the feel of them.
Apparently they only conferred an advantage at a certain slow cadence, at least that's what was said.

[123malford]

So did they feel normal so to speak ? Eyes closed you wouldn't know whether you were riding elliptical or round ?

[Colin Jenkins]

The Shimano Biopace followed up on a chainring on the UK market in the early 1950s - I think it was the Durham Bullseye, but may stand to be corrected. The Shimano design shifted the dead spot 90 degrees relevant to the earlier design. Neither of them achieved any tangible improvements that I'm aware of. I have a Biopace in use now and wouldn't notice its presence except for the badge on the chainring. No better or worse than any other chainring, and not worth searching about for one.

Best regards,

Colin Jenkins.

[meic]

I had them for the first 6,000 miles on my first adult bike. I dont recall noticing a difference when I got my second bike or when I replaced the Biopace rings on my first bike.

At first I thought I had to replace them with Biopace rings but of course you dont.

I replaced the outer ring with a round one to try and cure a changing problem (Biopace mean you must have a larger vertical gap at the derailleur for part of the revolution).
Even running a combination of Biopace and round I dont recall any noticeable difference.
I also sometimes rode my wifes bike with "Cycloid" rings on, which are eccentric the opposite way to Biopace, without noticing the difference.

Most of my riding is on hills.

[Swallow]

I had them on my Raleigh Randoneur, can't say I ever felt any difference

[nicmarsh]

I still have them , on a 52 - 42, and would say its the least noticeable difference between bikes when switching, far less noticeable for instance than gear ratios, spread and quantity or handlebar type and size or wheels even. I like them too I have to say!

[MikeF]

I have a one bike with them. I like them. The pedalling action "seems" to be very smooth. Actually it isn't because the pedal movement slows at the top and bottom of each turn. But this is the point where your legs change direction and so this abrupt change of direction is slowed. When you are pushing down (or pulling up) on the pedal the gearing is slightly lowered. There's not a big difference between them and round rings.

[Gearoidmuar]

So did they feel normal so to speak ? Eyes closed you wouldn't know whether you were riding elliptical or round ?

The felt different. When you cycle normal rings there's a short effort peak of resistance. It's noticeably longer with biopace.

[Ayesha]

The world has not yet decided their optimal degree of ellipse and orientation.

This is because every cyclist in an individual orgamism. A circular chainring encompasses all variations.

[Dynamite_funk]

I have them on my touring bike in 48,38,28. Climbing is definitely smoother and 'easier' somehow. This could be that the cranks are 0.5cm shorter (170mm as opposed to my usual 175) or that the middle ring is 1 tooth less but I haven't got the time to really bottom it out

[[XAP]Bob]

The world has not yet decided their optimal degree of ellipse and orientation.

This is because every cyclist in an individual orgamism. A circular chainring encompasses all variations.

Technically a circle is just a special case of an ellipse (the two foci are identical)

So it caters for as many variations as any other shape (OK, a few more since it has perfect rotational symmetry)

[Sooper8]

I have them on a Raleigh hybrid from late 80's- I can't honestly say I can tell the difference, but they are fine