Bike cranks and electric bike

Electric bike: the motor axle standard decides

On an electric assistance bike, the crank attaches directly to the motor axle, and it is this that determines the standard. The ISIS, a ten-tooth splined axle, is used on most Bosch and Brose motors: this includes the FSA CK, Samox, and Stronglight Magan4. The JIS, with a square axle, is found on Yamaha, Panasonic, and Ananda motors that the Stronglight Magan3 targets. Shimano designs its own cranks for its Steps motors, with models intended for a twenty-four millimetre axle. Therefore, before ordering, check the brand and generation of the motor, and then the desired length, which is most often one hundred and sixty-five or one hundred and seventy millimetres.

The rest of the pedalling

Pedalling parts also come in various types:

• Cranksets.
• Chainrings.
• Stars.
• Bottom brackets.
• Pedals.
• Accessories.

All parts can be found on the pedalling page.

Road and track: sensors, carbon, and spare parts

The Stages Power takes a left crank Shimano Dura-Ace and adds strain gauges that measure the force of the left leg, then estimate the total power; a simple coin battery powers it for over two hundred hours. The left cranks Shimano Dura-Ace, XT, and XTR can replace a bent part after a fall without replacing the entire crankset. Stronglight, whose history goes back to a steel crank manufacturer from the Saint-Étienne area in the early twentieth century, offers with the Track a pair of one hundred and seventy millimetre cranks for track and fixie. The Praxis carbon crank, finally, reduces weight without sacrificing stiffness.

Crank length and BMX racing

Crank length is measured from the centre of the bottom bracket axle to the centre of the pedal hole. On the road, it usually varies from one hundred and sixty-five to one hundred and seventy-five millimetres: a short crank promotes a high cadence and opens the hip angle in an aerodynamic position, while a long crank gives more leverage but closes the knee at the top of the pedal stroke. In BMX racing, the Insight and Box aluminium cranks are also chosen according to the rider's size and must withstand explosive starts from the grid: their stiffness is as important as their weight. Lastly, check compatibility with the existing bottom bracket.

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Frequently Asked Questions

What crank length should I choose based on my height?

Shorter cyclists benefit from one hundred and sixty-five millimetres, while taller riders can go up to one hundred and seventy-five. One hundred and seventy remains the most common length for an average height.

How to remove a bicycle crank without a puller?

On a square or splined axle, a puller is essential: hitting it with a hammer can damage both the axle and the crank. On side-clamping cranksets, just loosen the pinch bolts and then the preload cap.

What does the offset of an electric bike crank mean?

It is a lateral displacement of the arm, five millimetres for example on the Samox, which adjusts the chainline or foot spacing. It must match the frame and chainring fitted on the motor.

What torque should I use to tighten a crank?

Follow the value indicated by the manufacturer, often engraved on the crank. On a side-clamping Shimano crankset, the pinch bolts are tightened to around twelve to fourteen Newton-meters, alternating the two bolts.

Can I replace just one crank?

Yes, the left crank can be changed alone if it matches exactly the axle standard of the old one. The right crank, often joined with the chainrings and axle, usually requires replacing the whole crankset.