Hi if the pedals arent fully tightened they can fall off.
Pedal arm fell off bike.
If you are using an allen wrench insert the head of the wrench into socket located on the pedal arm.
Also the left side is reverse thread so now you will need to replace the pedal and the crank arm since its stripped.
Loosen the pedals by turning the right pedal counterclockwise and the left pedal clockwise.
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If your crank arm just keeps on falling off even after you ve asked your muscle building neighbour to tighten that nut as if his life depended on it there is one simple reason.
If you don t know what type of crank you.
Remove the pedal from the socket.
If you are using a smart wrench place the jaws on the nut located between the pedal and pedal arm.
Crank loose falls off if your crank arms flop with every pedal stroke or if you can wobble them from side to side fix them now before they become irreparable.