BIOPACE vs ROTOR

GSAstuto

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Oct 11, 2009
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#1
I scored a NOS Biopace 52T Chainring. I'm interested to compare this to a ROTOR. Anyone a willing test dummy? Seems that <ir>relevant technology gets circulated about every 20yrs - so this makes sense. But hey - who knows??
 

GSAstuto

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#4
@Pete - nope! These have been out of production for about 20yrs. I have some NOS ones, though. Interestingly, Shimano set their high-effort zone at the 'dead spot' , while Rotor and other companies set the low-effort zone at the 'dead spot'. Since Shimano has the patent on the asymetric , 'non-round' rings, so the other guys have to settle with variations of ellipse. I'm looking at these from a purely 'how do they feel' perspective and also perhaps as potential Enduro / TT refit for our team guys. Back in the day we'd just rotate the chainring back one or 2 positions to get the power stroke where we wanted it. If you are a steady -state kinda rider, they <seemed> to be helpful. I want to check and see if I still get that feeling or performance tweak.

They do work pretty good on fixed gear as well (my original thoughts) especially for high rpm spinning as it evens out the velocity your legs travel.
 

stanc

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#6
Interestingly, Shimano set their high-effort zone at the 'dead spot' , while Rotor and other companies set the low-effort zone at the 'dead spot'.
I had Biopace on my last touring bike. I remember when everyone worked out that Shimano had them designed wrong & rotated them. Didnt make any difference to me, I hated them. Probably didnt help that only the outer was Biopace. The other two rings were round :)
 

GSAstuto

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#7
I think its worth a revisit. I'm thinking to conduct several on the road tests with 3 rings - ROTOR, BIOPACE and ROUND. TT TEST, HC TEST and ROULER TEST. The protocol is very simple - I'll use a PT Wheel for data aquisition , then compare results of power vs. time.
 

Gunjira

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Oct 2, 2009
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#8
I think its worth a revisit. I'm thinking to conduct several on the road tests with 3 rings - ROTOR, BIOPACE and ROUND. TT TEST, HC TEST and ROULER TEST. The protocol is very simple - I'll use a PT Wheel for data aquisition , then compare results of power vs. time.
For what it's worth, I still have a set of used (not by me) biopace chainrings inner and outer for experiments.
When I get my Rotors depends on the gods of eBay. My biggest concern is: can you sprint on them?

Plan B is to use it single chainring with an Alfine hub in the back.
 

joewein

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Oct 25, 2011
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#10
Plan B is to use it single chainring with an Alfine hub in the back.
Correct me if I'm wrong: Does an elliptic chain ring not result in a variable amount of chain slack that has to be picked up by a rear derailleur? A simple cog at the rear as in an internally geared hub or single speed or fixed gear would not do that. So I seriously doubt this would work with an Alfine.