When a hub motor finally gives up, most riders search for "e-bike motor" and get two very different products back. One is a bare hub motor — the motor shell and axle on their own. The other is a motor wheel, sometimes listed as a wheel assembly: the same motor, already laced into a rim with spokes, ready to take a tire.
They can look nearly identical in a listing photo. They are not the same job once the box is open.
The difference is one skilled step: lacing
A bare hub motor has to be laced into a rim before it can be ridden. Lacing means cutting or sourcing spokes of the correct length, threading them in the right pattern, then tensioning and truing the wheel so it runs straight and stays that way under load. It is a real wheelbuilding skill, and it needs a truing stand and a tension meter to do properly.
A motor wheel skips that step entirely. It arrives laced and trued. You move your tire, tube, and cassette or freewheel over, drop it into the frame, and connect the cable.
That is why, for most riders replacing a dead motor, the motor wheel is the safer buy. The bare motor is the better buy only if you can lace a wheel yourself, or you have a shop that will do it for you, or you specifically want to keep the rim you already have.
Measure three things before you order either one
This part matters more than the wheel-versus-motor choice, because getting it wrong means the part does not fit at all.
1. Rear dropout spacing
Take the rear wheel out and measure the clear inside width between the two frame dropouts, with calipers or a steel rule. You will get one of three numbers:
- 135 mm — standard narrow-tire frames
- 170 mm — one fat-tire standard
- 190 mm — the wider fat-tire standard
170 mm and 190 mm are not interchangeable. This is the single most common and most expensive mistake in this category. Forcing a 190 mm motor into a 170 mm frame — or spreading a frame to make it fit — can deform the frame and will not clamp the axle properly, which is a genuine safety problem, not just a fit annoyance. Some motors ship with spacer washers that allow a 170/190 adjustment, but not every model does, so confirm before ordering rather than assuming.
2. Wheel diameter
Read it off the tire sidewall: 20", 24", 26", 27.5", 700c, 29". A motor wheel has to match your bike's existing diameter, because it comes with the rim already attached. (A bare motor is more flexible here, since the rim is chosen at lacing time — that is one of its few genuine advantages.)
3. Tire width, which drives rim width
Diameter alone is not enough. A 20" narrow-tire wheel and a 20" fat-tire wheel are entirely different parts: rim widths differ by more than double (roughly 25–35 mm for narrow tires versus around 82 mm for a 4.0" fat tire), and the dropout spacing differs with them. Always state diameter and tire width together.
One more to note while you have the wheel out: axle diameter, typically 12 mm or 14 mm. A 14 mm axle needs dropout slots wide enough to accept it.
Fitting mechanically is not the same as working electrically
A motor that bolts into the frame can still fail to run. The motor cable carries three phase wires plus five hall sensor wires, and the connector and pin order have to match what your controller expects. If you are pairing a new motor with an existing controller, read our guide to phase and hall wiring colour codes before you order, so you know what you are matching.
Riders whose original brand has stopped supporting their bike run into this most often; if that is you, our notes on sourcing replacement parts after a brand shuts down cover the same ground from the compatibility side.
Before you touch anything
Power off, remove the battery, and wait thirty seconds before disconnecting any motor cable. Connecting or separating phase wires with power present can arc and destroy the controller's output stage. After any electrical work, test the brake cutoff at low speed in an open area before riding normally.
Still not sure which one you need?
Send us four photos — your display, its connector, your controller label, and your motor cable — plus your dropout measurement and tire size, and we will confirm the fit before you order. You can browse what is currently in stock under Motors & Wheels, and the calipers and axle wrenches for taking these measurements are in Tools.
RideRow sells parts and provides installation information. We do not perform repairs.