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Changin old biopace chainrings(3 posts)

Changin old biopace chainringskilimanjaro
Feb 27, 2002 9:49 PM
I want to replace my old 105 biopace chainrings. I took them off and will check local LBS for compatible chainrings.


1) How do I measure BCD

2) If I replace with chainrings with different teeth count, do I need to adjust the FR or shorten/lengthen the chain,

Thanks and regards,
re: Changin old biopace chainringsAndy M-S
Feb 28, 2002 6:05 AM
Do you want to replace them with new BioPace or with standard round chainrings? If you want new BioPace rings, I might be able to help you (there's a set on a bike I'm setting up for my daughter and I wouldn't mind replacing them). If you want round rings, I'd highly recommend Stronglight, but the choice is yours.

1. (Almost) all Shimano road cranks use a 130 bcd, so that's probably what you have. I'm (fairly) certain that is the only size in which BioPace rings came.

2. You may need to move the FD up or down so it tracks closely on the rings; you might need to adjust the chain a little, but probably not--unless you're going to replace the rings with something radically different from what you have.
Andy's right--it's pretty much a straight swapRetro
Feb 28, 2002 8:20 AM
My wife's mountain bike had Biopace until last week--she wouldn't let me change them until they just flat wore out. I forget the BCD, but it's a common one and there are jillions of rings available. Moving the front d. up or down a little as required is about all you'll have to do.