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Old 02-12-19, 01:19 PM
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CliffordK
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I haven't seen any indication of indexing of octalink V1, V2, or ISIS. If it is there, it is mighty subtle. Perhaps I'll have to try measuring one with calipers.

there was something that I ran into that was indexed like that. Car steering couplings are often indexed (but not necessarily steering wheels). I think some of the through-axle designs also have a similar indexing.

As far as the foot forward thing.

Right crank connected to chain. Bottom bracket just stabilizes it. Pedal back with right only, and it freewheels (or tensions chain on a fixie). Pedal forward, and torque taken up by the chain.

When pedaling forward with the left crank, it causes a counter clockwise rotation (from left side) at the left crank to bottom bracket, and then through the bottom bracket, and again at the right crank to bottom bracket interface.

Back pedalling with the left crank, and one gets a clockwise rotation on the bottom bracket/left crank, and at the the bottom bracket/right crank interfaces. That is probably OK if you are freewheeling, but would tend to twist the bottom bracket in relation to the cranks if braking (fixie/pedal brakes), or standing on the pedals with the left back.

Say you achieve 0.01° rotation at the crank/spindle location, then repeatedly hitting that +/- rotation could tend to wear the aluminum crank interface.

If this is an issue, then I'm surprised to hear that the Octalink is being used with fixies.

Square taper wouldn't be vulnerable to this as it is a press-fit (unless hollowed out).

The new through-axle (24/30mm) crank designs would also be less susceptible due to tightening down bolts for Shimano style cranks, and the triangular interface for Campy style cranks.
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