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mixing Biopace granny gear with ramped/pinned middle and large

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mixing Biopace granny gear with ramped/pinned middle and large

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Old 06-20-10, 12:35 PM
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XC2007
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mixing Biopace granny gear with ramped/pinned middle and large

I am preparing our tandem for a self-supported credit card tour and want to gear it down more. I run Ultegra triple crank with 52/42/30 and have a Biopace 28 ring I'm considering switching to. I have run a round 26 on this before.

Since granny is used 'regularly' but rarely in an emergency and shifting to middle is always done with no stress, is this idea so silly? Won't I get more power since our cranks are in-phase?

Thanks!
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Old 06-20-10, 12:42 PM
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People have different opinions on Biopace. Some will tell how much they'll change your life. Others will say how stupid they look.

All I can say is that they should work fine with your other components. Whether they help or not you'll have to judge for yourself.


One thing occurs to me, though. You imply that only one granny will be changed. True? False?
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Old 06-20-10, 01:31 PM
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I'll keep the large and middle rings as is. When I rode cross-country with my son we kept the cranks out-of-phase which helped in the Rockies. With my wife in Glacier NP, I know she likes to be in-phase, so I was considering just changing the stock 30T granny to either the Biopace 28T or round 26T I have. I was curious about shifting problems with a granny Biopace to a round middle ring.
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Old 06-20-10, 04:10 PM
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I don't see how changing the granny ring would affect staying in-phase or not. It's not like your talking about changing either of the chainrings on the left (timing) side, are you?
Anyway, the move from Biopace granny ring into the round middle ring will feel strange, but if you plan to be in the biopace ring for long climbs, and you like the feel of climbing that way, then make the switch.
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Old 06-20-10, 05:17 PM
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The timing rings will not change. I think protracted climbs, as we did in Montana, require sitting the whole way up. A Biopace granny theoretically gives us more power only if we're in-phase. So if the shifting works from that exaggerated Biopace 28T granny to the round ramped/pinned 42T, I think I'll try it.
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Old 06-21-10, 01:00 PM
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I haven't heard any complaints about shifting from Biopace to round. Good luck!
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Old 06-21-10, 01:08 PM
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It shouldn't be a problem. Shifting might be a little more clunky...but it will work. You'd probably benefit most from lowering your gear ratios. I like biopace.

I'd suggest 46/36/26
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Old 06-21-10, 02:37 PM
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I've used a middle Biopace ring (38) with round outers (52 and 50) and didn't see much of a change in shifting compared to a round 39.

You may need a chain watcher on there for the downshifts to the Biopace granny (or for the round 26 for that matter).
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