Thread: Equipment/Product Review (1988) SHIMANO Biopace
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Old 10-15-23 | 06:51 AM
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tcs
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From: Parts Unknown

Bikes: Mike Melton custom, Alex Moulton AM, Dahon Curl

Originally Posted by pastorbobnlnh
I've been hunting for a 50T or 51T Biopace outer ring (130BCD) and any inner Biopace road rings (42T, 43T, 44T, etc.).

"50T, 48T, 46T, 44T, 38T and 36T chainrings were made in the 110mm bolt circle diameter; 28T and 26T chainwheels in the 74mm bolt circle diameter. These chainrings were generally used in triple cranksets: the 74mm bolt circle is only used for the innermost chainring of a triple. However, the outer chainring may be left off or replaced with a chainguard/protector plate (like a toothless chainwheel) for a wide-step double.

"Sizes 53, 52T, 42T and 40T (that one only in steel) were made in the 130mm bolt circle and were generally used in racing doubles, though some cranksets have a 130mm outer and 74mm inner bolt circle. Few front derailers could handle a 52T outer and 28T inner Biopace chainwheel, though." - Sheldon Brown
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