Electric Bicycle (ebike) Conversion Kit assembly - hub motor, controller and battery pack installation

Step 4 Measure the front fork spacing

Most hub motor axles are 130mm to 135mm to match the majority of forks. You can add washers to either side of the hanger to take up slack or to compress the forks so long as you do not exceed a total of 10mm or 2 hanger widths whichever is greater. Otherwise you will again have to go looking for a more suitable frame.

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Comments

[zenithfab]

The "over locknut dimension" on most front hubs is 100mm. Which should closely match the inside of the forks. The "OLD" of the rear hubs on most newer bikes is 130 or 135mm, 130 for many road bikes, 135 for mountain types. Again matching the rear dropouts.

[watermelon]

Some electric rear hub motor over locknut dimension will require 160mm spacing if the axles used were designed for tandem bikes with 160mm standard spacing. Some manufacturer's now claim to offer 130mm and 135mm rear hubs with new Lithium Iron Phosphate batteries. The main issue with front hubs is fork material, suspension and taper.
(See Sheldon Brown)
91 mm Low-end front hubs.
96 mm Older front hubs, especially French.
100 mm Modern front hubs.
110 mm Rear older track, coaster brake and other single-speed hubs. Also, front hubs for Downhill bikes with 20 mm axles.
114 mm Rear 3-4-speed .
120 mm Rear 5-speed, Ultra 6, newer track hubs.
126 mm Rear 6- and 7-speed (road).
130 mm Rear 7-speed (MTB) and 8- 9- and 10-speed (road).
135 mm Rear 7- 8- and 9-speed (MTB)
140 mm Rear tandem.
145 mm Rear tandem (newer models.)
150 mm Retro-Choppers, some Downhill and Freeride models.
160 mm Rear tandem (new Santana proposed standard.)