The reason we’ve supplied a 10mm axle is because almost all bike axles are within 1mm of the standard 10mm. It’s important that it’s a very snug fit to prevent the axle from spinning and we didn’t want to risk delivering to anyone an axle that is loose and might cause damage. That’s why we’re asking you to file off 0.5mm from the flats of your axle such that it will fit your forks.
Firstly, check the orientation of the wheel such that the flats of the axle are between the forks.
Our motor has the standard 10mm axle diameter, which may not fit a limited number of fork models. Our advice for this scenario is to carefully file the flats on the motor axle, making sure not to damage the thread. It is likely that your forks have a 9mm slot width, therefore you will just need to take off 0.5mm on each side of the axle and torque washers to get it down to the correct fit.
Here is a video that guides you through the entire process. Please make sure the watch the video in full before attempting the filing yourself.
We advise against filing the fork slots themselves as this can introduce microfractures into the material, which may mature into cracks and cause a failure further down the line - we obviously want to avoid this.