Shimano BioPace Chainring 52t, 130 BCD, Gunmetal Gray

Very lightly used.  Anodizing is only half worn from the teeth.  A few minor scratches here and there.  Tons of life left, should mesh with a new chain well.. Still has the original price sticker from Bill's Bike Shop in Twin Falls, ID.

BioPace chaiinrings were popular in the late 80's and early 90's.  Many people still swear by them to this day!  They came on many 105, 600/Ultegra, Dura Ace, Deore XT, Exage, etc cranks from 6, 7, and 8 speed drivetrains.

BioPace was the exact opposite of the standard elliptical chainring.  BioPace rings are actually EASIER on your knees than a standard round ring.  The smaller radius is engaged with the chain when the cranks are horizontal, and the large when the cranks are vertical.  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.  See this page for more technical details.

• 52T
• BCD: 130mm
• 5-bolt
• Color: Anodized Gunmetal Gray