Shimano Biopace chainrings in 74, 110 & 130mm Bolt Circle Diameter (BCD)

On this page: 74mm BCD Biopace rings | 110 BCD Biopace rings | 130 BCD Biopace rings
SR & Sugino elliptical chainrings are posted here.

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Shimano Biopace chainrings brilliantly solve the problems that purely elliptical chain rings present. Sheldon Brown gave an excellent explanation of how Shimano's engineers have taken a flawed century-old idea to create a wonderfully designed and superbly efficient chainring.

"Biopace is a patented non-round chainwheel design made and licensed by Shimano. To a casual glance, Biopace chainwheels resemble elliptical chainwheels, but on closer examination they turn out to be the opposite of the classical elliptical design. The product of extensive research and computer-aided design, Biopace chainwheels have the small radius engaged when the cranks are horizontal, the large when they are vertical. This is because the Biopace design is based on a dynamic analysis of the motion and momentum of moving cranks and legs, unlike the static, geometric analysis that produced classical ellipticals.

"The theory is that during the power stroke, when the cranks are more or less horizontal, you are using the power of your legs to accelerate your feet, which get going quite fast in the lower gear provided for that part of the stroke. The momentum of your feet then carries the pedals through the "dead spot" when the cranks are near vertical. Since the rider doesn't push as hard during the power phase of the stroke, and motion is slower when the leg is changing direction, the Biopace design is gentler on the knees than even round chainwheels."

If you are unsure about what size chainring you need, Wolf Tooth Components has an excellent guide to measuring your rings.

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74mm BCD Biopace Chainrings: 28 tooth

28-tooth, 74mm BCD Shimano Biopace chainring.

We have several: Used | Steel used #1 (black) | #2 (black) | #3 | #4

28-tooth, 74mm BCD Shimano Biopace chainring. used, $25.00

Many hills left in this ring.

And the ring turned over.

28-tooth, 74mm BCD steel Shimano Biopace chainring #1. Used, $25.00

Lightly used

The flip side.

28-tooth, 74mm BCD steel Shimano Biopace chainring #2. Used, $25.00

Light use

And the same ring flipped over

28-tooth, 74mm BCD steel silver Shimano Biopace chainring #3. Used, $25.00

Front side

The back side

28-tooth, 74mm BCD steel silver Shimano Biopace chainring #4. Used, $15.00

Side 1

Side 2

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110 BCD Biopace chainrings: 48 tooth | 50 tooth

48-tooth, 110 BCD Biopace chainrings.

We have several: Used #1 | Used #2 | Used steel

48-tooth, 110 BCD used Biopace chainring #1, $50.00

Top side

And the back side.

48-tooth, 110 BCD used Biopace chainring #2, $50.00

Lovely condition

And the back side of the same ring.

48-tooth, 110 BCD steel Biopace chainring. Used, $15.00

Inexpensive and will last for nearly all time. Nearly, but not quite.

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50-tooth, 110 BCD Biopace chainring. Lightly used, $50.00

It's had just a little use.

And it looks just as good flipped over.

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130 BCD Biopace chainrings: 42-tooth | 52-tooth

42-tooth, 130 BCD Biopace chainrings.

We have several:
New (all were taken off new bikes) #1 | #3 | #4
Used: #1 | #2 | #4 | #5 | #6 | #7 | #8

42-tooth, 130 BCD Biopace chainring #1. New, $50.00

Taken off a new bike.

Side one.

And the flip side

42-tooth, 130 BCD Biopace chainring #3. New, $40.00

Taken off a new bike.

Side 1

Side 2

42-tooth, 130 BCD Biopace chainring #4. New, $40.00

Taken off a new bike.

Side 1

Side 2

42-tooth, 130 BCD used Biopace chainring #1. Used, $25.00

Front side

And the back side

42-tooth, 130 BCD used Biopace chainring #2. Used, $25.00

Front side

And the back side

42-tooth, 130 BCD used Biopace chainring #4. Used, $25.00

Side 1

Side 2

42-tooth, 130 BCD used Biopace chainring #5. Used, $25.00

Been on a bike, but it has lots of miles left.

And here it is flipped over

42-tooth, 130 BCD used Biopace chainring #6. Used, $25.00

The business side with the specs

And the same 42-tooth ring flipped over

42-tooth, 130 BCD used Biopace chainring #7. Used, $25.00

Side 1

And side 2

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42-tooth, 130 BCD used Biopace chainring #8. New, $25.00

A lot of miles left in this ring.

Here's the other side

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52-tooth, 130 BCD Biopace chainrings.

We have several:
New: #1 | #2 | #3 | #4 | #5
Used: #1 | #2 | #3 | #4 | #5 | #6

52-tooth 130 BCD Shimano Biopace chainring #1. New, $80.00

New, in its factory package.

And out of its package for a close-up

52-tooth 130 BCD Shimano Biopace chainring #2. New, $80.00

Factory fresh

Mr. DeMille, I'm ready for my close-up.

52-tooth 130 BCD Shimano Biopace chainring #3. New, $80.00

Available in silver, as well.

52-tooth 130 BCD Shimano Biopace chainring #4. New, $80.00

This taken off a new bike.

52-tooth 130 BCD Shimano Biopace chainring #5. New, $80.00

This was taken off a new bike.

52-tooth 130 BCD Shimano Biopace chainring #1. Used, $25.00

Top side

And the back side

52-tooth 130 BCD Shimano Biopace chainring #2. Used, $25.00

Used, but only a bit

And just as nice on the back side

52-tooth 130 BCD Shimano Biopace chainring #3. Used, $25.00

The business side

And the back side

52-tooth 130 BCD Shimano Biopace chainring #4. Used, $25.00

Lightly used

And the same ring flipped over

52-tooth 130 BCD Shimano Biopace chainring #5. Used, $25.00

Front side

And the back side

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52-tooth 130 BCD Shimano Biopace chainring #6. Used, $25.00

Side one.

And side two