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So, I wonder what happen if I replace my left crank with another right crank (either Square tapered or ISIS splined wouldn't matter).

What is the disadvantages apart from: 1) the pedal thread loosening over time (can be fixed using thread locking and hope it works..)

Please list any other problems I might have overlooked

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    If you leave the sprockets on it may interfere with the frame, since the right-side crank shaft is often longer than the left. – Daniel R Hicks Nov 18 '14 at 4:21
  • Actually the problem on the pedal is opposite - it would tighten. You pedal pedals off not on. – paparazzo Nov 18 '14 at 15:36
  • You would need two right-pedal spindles, and would have to either rebuild your left pedal onto a right spindle, or have only platform pedals. – Criggie Apr 10 '19 at 19:53
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Well, you'd have a spider on both sides is one odd and annoying thing. Sheldon Brown has run the cranks in reverse on regular (non-bmx) bikes [In BMX, there is a reasonable set of options going both ways].

You'd also probably get a strange Q-factor as well given that the insertion depths are different for the right and left crankarms. This could be compounded if you happen to have a non-symmetrical spindle length bottom bracket.

(It should work in theory - why you'd want to do this in practice unless you were in the odd situation of having two good right crank arms and no good left crank arms is a mystery...)

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  • I would like to make a motor with freewheel mechanism to drive the left side. – Nhân Lê Nov 18 '14 at 1:33
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    You should get a bottom bracket, spindle and rear (stoker) crankset for a tandem. They have spiders for chainrings on both sides and correct pedal threads. – Carel Nov 18 '14 at 8:43
  • @carel Downside there is the pedals will rotate with the motor, and you can't freewheel or coast. That would be uncomfortable at higher speeds. – Criggie Dec 1 '15 at 19:57

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