Shifting derailleur without pedaling?

Question

I know shifting gears without pedaling would potentially damage your bike, but would shifting front derailleur while stationary damage anything?

Answer 1

Depends on the direction.

I have found that on electric bikes, when using the maximum assist level, if pedaling only slightly, there is so much electric assist that the electric assist alone prevents me from shifting from the big ring to the little ring. The easiest way to shift in this case is to stop pedaling, shift, and resume pedaling. The interruption in pedaling allows the front derailleur to move, which would be otherwise prevented by the huge tension on the chain caused by electric assist. The reason this is safe is that downshifting to a smaller ring only releases tension on the cable. There is nothing that could break.

On the other hand, if you upshift to a bigger ring without pedaling, especially if upshifting twice on a triple crankset, all of the tension of the derailleur against the chain goes to the cable. You may break a shifter that way.

Answer 2

Shifting a single gear in either direction without pedalling won't damage anything. Either the cable or chain will take up the discrepancy by bending. (Shifting two gears up on a 3× system is another story, that can indeed damage the derailleur.)

Of course it won't actually shift to the desired gear, so there's no point in doing that. And if you then start pedalling, it may well jam / jump the chain. So don't do this. Front derailleur shifts should always be done while spinning one crank at reduced torque. If you find yourself having to stop suddenly and have to shift stationary before continuing, lift up the rear wheel and have it rotate in the air whilst doing the shift. This is easiest done by putting one foot one the ground, the other clipped in, front brake locked to push the handlebars forward with both hands. Alternatively get off the bike completely, pull the rear up by the saddle and spin the cranks with the tip of your foot.