Geared hub motor should work with 3x7 speed. If you want to use your old cassette/freehub you need to make sure the kit has the appropriate fitting. The cost of a new cassette/freehub isn't that much anyway.Hi nice too meet you, could you please tell me how geared motor works and also would this work with a 21 speed (3x7) and what will I need to buy thanks, sorry I'm a noob
Geared hub motors have gears internal to the hub motor. Fixed gearing, just so the motor can run fast (which electric motors prefer) without turning the wheel too fast. The one thing the direct drive ones (such as that Voilamart) are good at is going illegally fast on the flat.
I second the suggestion to buy from Woosh; our tandem kit came from them. You'll get help about the best kit to buy for your situation, and excellent advice if you need help fitting, and service if anything does go amiss later. You'll know all the bits work properly together, and there won't be complications with VAT/import/etc.