Published fitment, side by side
The columns that matter are the first three. Everything else about these kits is broadly the same.
| Kit | Wheel sizes published | Motor type | Rear spacing | Gearing | Battery |
|---|
| Bafang 48V 500/750W Rear Hub Kit | 20, 26, 27.5, 700C, 28, 29 in | Direct-drive rear hub | Standard rear spacing | Not stated in the listing | Not included |
| Bafang G062 48V 750W Fat-Tire Kit | 20 x 4 in fat wheels only | Rear hub, wheel included | 175 mm | Takes a cassette | Not included |
| Varstrom 48V 500/750W Geared Rear Kit | Rear hub kit | Geared brushless rear hub | Standard rear spacing | Not stated in the listing | Not included |
Note what is notin that table. Not one of these three listings publishes a torque figure in newton-meters, a controller amp rating, an efficiency number or a motor weight — and none cites a test behind the 500/750 W switch. That is normal for this category and it is the reason this page ranks on fitment and support rather than on performance: fitment is published and checkable, performance is not.
Geared or direct drive: the one spec difference that you will feel
The Varstrom kit is a geared hub, the Bafang kits are direct-drive, and this is a genuine ride difference rather than a marketing one.
A direct-drive hub is a motor with no gearbox: the axle is the stator and the shell spins around it. It is simple, quiet and very durable, and it can regenerate a trickle of charge downhill on some controllers. Its cost is that the magnets drag slightly whenever the wheel turns, so with the power off — flat battery, fuse pulled, motor cable unplugged — you can feel it.
A geared hub puts a small planetary reduction and a freewheel inside the shell. The freewheel is the point: with the power off it spins like a normal wheel and the bike rides like a bike. It is also lighter and climbs better at low speed for the same watts, and it trades that for more moving parts and more noise. On a conversion specifically, we rate the freewheel highly, because the whole premise of a conversion is that you keep a bicycle you like — and a bicycle that becomes hard work when the battery dies 12 miles out is not the bike you kept.
What you still have to buy
Budget for all of this before deciding a conversion is cheaper than a complete bike.
- A battery.The big one. Match the voltage to the kit — 48 V kit, 48 V pack — and read are e-bike batteries interchangeable before you buy, because the connector, the BMS discharge rating and the mount all have to agree, not just the number on the label. Our battery picks are the packs we would pair with these kits.
- A charger that matches. Usually included with the pack, not with the kit. If you need a second one, our charger picks cover the voltages and connectors.
- A torque wrench. Rear axle nuts on a hub motor are the one fastener on a bike where under-tightening can let the axle spin in the dropout and destroy the frame. Our torque wrench picks include the honest warning that hub-motor axle torque is often above the range of a bicycle torque wrench, so read your kit’s figure first.
- Possibly a torque arm.A 750 W hub in aluminum dropouts is the classic case for one. It is cheap insurance and it is not in any of these boxes.
Which donor bikes convert well
The kit is the easy part; the bike decides whether the result is good. Three things to check on the bike in your garage.
Brakes.A converted bike is heavier and faster than it was designed to be. Rim brakes on a 750 W conversion are the part of this project we would not accept — disc brakes, ideally, and at minimum brake cut-off levers wired into the controller so the motor cuts when you pull the lever.
Frame material and dropouts. Steel takes hub-motor torque more forgivingly than thin aluminum. Vertical dropouts on a quality frame are fine; soft, thin or already-cracked dropouts are not a conversion candidate at any price.
Whether the bike is worth it.This is the real test and it is the one people skip. A conversion costs roughly the same as a budget complete e-bike once the battery is in the basket, so it only wins when the donor is a bike you genuinely like — the right size, comfortable, sound. Converting a cheap department-store bike gets you a heavier cheap bike that now goes 20 mph. Our mountain-bike conversion guide walks the fitment checks on the most common donor of all.
What we would actually buy
Standard bike, want it to last: the Bafang 48 V 500/750 W rear hub kit.Widest published wheel fitment of the three, and the brand whose controllers, displays and spares are easiest to replace in a few years’ time — which, on a part you are bolting to a bike you love, is worth the premium.
Fat-tire donor: the Bafang G062.Not an upgrade over the standard kit, a different part. 175 mm spacing, a 20 × 4 wheel in the box, cassette and disc compatible so your gearing and brakes carry over. Measure your frame and your tire before ordering, because it fits 20 × 4 and nothing else.
Tightest budget, or you want it to coast: the Varstrom geared kit. Meaningfully cheaper than the Bafang, and the freewheel is a real advantage on a converted bicycle. You give up Bafang’s parts ecosystem, which matters more the longer you plan to keep it.
And if you want the full kit-with-battery route instead of sourcing a pack yourself, our conversion kits with a battery included page covers the bundles, and our main conversion kit roundup is the wider field.
