Will a motor kit work on my bike?
Most bikes can be electrified, some more easily than others. Certain electric kits are better suited to bikes with particular characteristics, while other kits can be installed on almost any bike. Here are some things to look for on your bike:
Type of bike. Rigid mountain bikes with steel frames, or hybrid/town/commuting bikes with flat or upright handlebars are ideal. The bike must have standard frame spacing (100mm front or 135mm rear), standard dropout width (10mm between the flats), and dropouts that are deep enough to accept a motor axle (at least 12mm, preferably 14-15mm). You cannot install a motor kit on a carbon bike or a full-suspension bike. Electric bike throttles work best on handlebars that are relatively straight; the components must be positioned so that you can reach the throttle, shifter, and brake without having to let go of the handlebar. Road bikes with drop handlebars are not generally compatible with electric kits, because you cannot easily install or use a throttle, and the frame spacing is usually narrower than is needed for a motor wheel. Pedal-activated motors like the BionX kit can work on bikes with drop bars, provided the rear frame spacing is 135mm. If your bike has a suspension fork, you can either use a rear motor, or swap out your fork for a rigid one. Folding bikes are also not generally compatible, because of wheel size, frame spacing, and the ability to carry cargo (like a battery).
Wheel size. The ideal bike for electrification will have a standard wheel diameter, either 26” (most mountain bikes, 559mm) or 700c (most road/hybrid bikes, 622mm). Motor kits are generally available prebuilt into these standard wheel sizes, so the kit is bolt-on-and-go. Some motors are also available in 20” wheels, for recumbent or folding bikes, though not all motors will fit in a rim that small. Other wheel sizes, like 24” or 27”, can be custom-built for an additional charge, but finding a sturdy rim will be more difficult because the selection is limited.
Drivetrain. Using a front hub motor eliminates the need to modify your bike’s drivetrain, and makes the overall installation much easier. If you prefer a rear motor, or require one because your bike has a suspension fork, you may need to change out your rear shifter/derailleur/freewheel for a combination that is compatible with the motor you choose. Larger motors like the Nine Continent/Hill Eraser can only accommodate up to 6 rear gears within the standard spacing. Medium-width motors like eZee and BMC can fit 7 or fewer rear gears. Thin-profile motors like BionX can fit up to 9 gears. Rear motors cannot be used in conjunction with internally-geared rear hubs or belt drives.
Carrying capacity. You’ll need to be able to carry 10-30 lbs of battery, securely mounted to prevent impact and vibration. A sturdy rear luggage rack is ideal. Check your bike frame for the standard mounting points for a luggage rack (one 5mm threaded hole on each side above the rear dropouts, and one 5mm threaded hole on the outside of each seat stay, near the top). Very small frames, old frames, or odd frame shapes may make it difficult to carry the necessary components for your electric kit.