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Biopace chainrings(6 posts)

Biopace chainringsseanf711
Aug 29, 2003 7:06 PM
I received for free an old Trek 420 that I am cleaning up to ride. I took the chainrings and cranks off to clean them up. I realized afterward that I didn't check the orientation of the rings. Does anyone know. Does the long side of the oval go parralel to the cranks or perpendicular?
re: Biopace chainringschipnseal
Aug 29, 2003 7:57 PM
Parallel to the cranks...Biopace was the hot topic of the mid 80's. I have an old Diamondback mountain bike that is my neighborhood beater bike. I actually take it out on the road as a training bike in really bad weather. The technique for spinning feels strange for a few miles.

Good Luck!
re: Biopace chainringslnin0
Aug 29, 2003 8:00 PM
When I look at mine the longer side goes with the crank. So when the crank is straight up or down the space between the f-d is tightest.
re: Biopace chainringsseanf711
Aug 29, 2003 10:46 PM
Thanks for the replies. I think I have it all together now.
What difference does it make?Alexx
Aug 31, 2003 6:14 AM
If it were my bike, I'd toss the stupid things into the trash can right away.
Look closely at each chainring.Spoke Wrench
Sep 1, 2003 11:42 AM
The big chainring has a metal dowell that goes on facing the crankarm. Smaller chainrings have a little "flat top bump" cut into the inner circumference that goes on facing the crankarm.