Frame and Weight: Which Bike Suits a Conversion

Steel and aluminium frames are suitable for a conversion, carbon is not (GIGA). A kit with battery often weighs 6 to 8 kg, and your bike has to carry that together with you and your luggage. Before you order, check the material, the total weight and the condition of the wear parts.

Identifying the material: the magnet test

Not everyone knows what their own frame is made of. The simplest test needs only a magnet:

1. Hold a magnet to the down tube.
2. If it sticks, the frame is steel.
3. If it does not, it is aluminium, carbon or titanium.
4. Tap the tube gently with a knuckle. Carbon sounds dull and hard, aluminium brighter. This is unreliable but gives a hint.
5. Look at stickers and welds. Aluminium often shows thick, "stacked" weld beads, carbon usually has no visible welds.

When in doubt, the frame's label or a question to the manufacturer helps.

Why not carbon

In a conversion, forces act in places the frame was not built for: the torque of a hub motor acts on the dropouts, and a mid-drive clamps into the bottom bracket shell and sends forces into the tubes. Carbon is strong in the direction the fibres run, but sensitive to clamping pressure and point loads. A crack is often invisible from the outside. That is why conversion is discouraged for carbon. It applies to frame and fork alike. With front motors especially, a carbon fork is a no-go.

Total weight

On top of the bike's own weight come kit and battery, often 6 to 8 kg (GIGA). Then there is you and your luggage. So check:

• The permitted total weight of the bike, usually stated on the frame, the rack or in the manual
• The load rating of the rack, if the battery goes there
• The load capacity of the wheels and spokes

If you are already near the limit without a conversion, that is a warning sign. Weight also lengthens braking distances. More on that under brakes.

Warranty

With a conversion, the bike manufacturer's warranty usually lapses (GIGA). On a bike that is still under warranty, that is a real disadvantage. Some workshops also refuse conversions because they count as a modification of the manufacturer's product. Find a conversion-friendly workshop before you start, and ask whether it will also service the bike later.

Replace wear parts before converting

A motor amplifies whatever is already weak on the bike. Replace worn parts beforehand (GIGA):

Build this into your budget. It also appears in the overview under costs as small parts and brake upgrade.

When a bike is not suitable

• Carbon frame or carbon fork
• Frames with cracks, rust at load-bearing points or badly bent dropouts
• Very light aluminium forks for front motors
• Bikes that are at their weight limit even without a motor

In these cases we say it plainly: leave it, buy a used e-bike instead. In the end that can be cheaper and safer.

Does a conversion fit your bike?

How reliable is this?

The suitability of steel and aluminium, the advice against carbon, the kit weight of 6 to 8 kg, the loss of warranty and the need to replace wear parts come from the linked source. The magnet test and the explanation of why carbon is a problem are worded as experience and assumption; Fabio is still checking them.