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

  • 2
    If you leave the sprockets on it may interfere with the frame, since the right-side crank shaft is often longer than the left. Commented Nov 18, 2014 at 4:21
  • Actually the problem on the pedal is opposite - it would tighten. You pedal pedals off not on.
    – paparazzo
    Commented Nov 18, 2014 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
    Commented Apr 10, 2019 at 19:53

1 Answer 1


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...)

  • I would like to make a motor with freewheel mechanism to drive the left side.
    – Nhân Lê
    Commented Nov 18, 2014 at 1:33
  • 3
    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
    Commented Nov 18, 2014 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
    Commented Dec 1, 2015 at 19:57

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