Converting a Dutch Bike to an E-Bike
A Dutch bike can usually only be converted with a front motor. The reason is the rear hub: the coaster brake and the hub gears live together there, and a rear or mid-drive motor either replaces or disturbs exactly that. Even so, the bike is a good candidate, because a steel frame and fork are usually sturdy.
What makes a Dutch bike
Typical features are a step-through frame, steel, a coaster brake with a 3-speed hub, a rack, a chain guard and a weight of around 20 kg. On many of these bikes the axles are held with nuts, not quick-release levers. At the rear, the dropouts are often narrower than the usual 135 mm; our example bike has 120 mm.
What usually works
- Steel frame and fork: a good basis, also for a front motor. You still need a torque arm at the front, see Torque arm.
- Rack: this is where the battery goes. For the example bike the configurator assumes a 36 V battery on the rack.
- Small budget: front motors are the cheapest motor type and need the least intervention.
- Relaxed riding: if you ride 8 km to work, you do not need a hill-climbing motor.
What it fails on
Coaster brake and hub gears at the rear. A rear motor replaces the hub. Then the coaster brake and the gears are gone, and most rear motors rule themselves out. For our example bike the configurator rates the rear motor red for that reason. More under Coaster brake.
Mid-drive. The motor usually contains a freewheel, which often puts the coaster brake out of action. Coaster-brake variants exist for individual models; that is an assumption Fabio is still checking. For the example bike the configurator rates the mid-drive yellow, not red.
Wheel size. Not every Dutch bike has the standard 622 rim. Old ones often have 635 (28" × 1 ½), and that does not fit 622 kits even though both are called "28 inch". Read the ETRTO number off the tyre, more under Wheel sizes.
Brakes. A coaster brake alone is mostly not enough for a heavier, faster bike. An extra front brake is often sensible, see Brakes.
Which motor type fits
For a Dutch bike with a coaster brake and hub gears, the front motor is the normal case. The coaster brake and the gears stay, and fitting is simple. The price: weight at the front, less traction on wet ground and gravel, and a changed steering feel. The fork has to carry the motor. Carbon forks and very light aluminium forks are not candidates, and with a suspension fork you need the manufacturer's approval. The trade-offs in detail: Motor types.
The configurator also rates a friction drive green for the example bike. It is light and removable, but has little power, wears the tyre and slips when wet.
What to measure first
- Front hub spacing (usually 100 mm) and the axle type, see Hub spacing.
- Rim size (ETRTO on the tyre), see Wheel sizes.
- Space for the battery on the rack, see Battery.
- Total weight: a kit with battery often weighs 6 to 8 kg (GIGA). Check the permitted total weight of the bike and the rack, see Frame and weight.
The law in short
A pedelec has at most 250 W rated continuous power and assists only while you pedal, up to 25 km/h. A throttle is only allowed as a walking aid up to 6 km/h. Anything above that counts as a motor vehicle, see Pedelec law.
When you should leave it
Leave it if the frame or fork has rust, the fork is carbon or unclear, or the brakes are already weak without a motor. A bike with 635 rims and worn-out wheels is also rarely a good conversion, because you end up paying for new wheels and brakes as well. Then a used e-bike is usually the more honest solution. Also keep in mind that the manufacturer's warranty mostly lapses, and some workshops refuse conversions (Fahrrad XXL).
How sure is this?
The statements on weight, warranty and workshops come from the sources listed. That coaster brakes and hub gears rule out most rear motors, and that a mid-drive often disables the coaster brake, is an assumption Fabio is still checking. The assessments for the example bike come from our configurator and are no guarantee for your bike.
Traffic light for an example bike
Example bike – yours may differ.
Calculated with our example bike “Dutch bike with coaster brake and 3-speed hub”:
Recommendation for the example bike: Front hub motor
Motor types at a glance
- Front hub motorFits
- Friction roller motorFits
- Mid-driveNeeds workThe freewheel inside a mid-drive often disables the coaster brake. Only a coaster-compatible version works.
- Rear hub motorDoesn’t fitAlmost no rear hub motor works with a coaster brake: the brake lives in the hub the motor replaces.
Main findings
- NoteA front hub motor always needs a torque arm, otherwise the axle can spin in the dropout.
- NoteWith a front motor your coaster brake stays. You need a good front brake.
- NoteThe bike maker's warranty usually ends after the conversion.