Why a bike's weight matters more than its gears

Ask a shop what makes a good children's bike and you will hear about gears, suspension and frame material. Weigh the bike and the conversation changes. A 16 inch bike from a supermarket often comes in at 11 or 12 kg; a specialist one at the same wheel size can be 6 or 7.

The ratio that explains everything

What matters is not the weight but the weight relative to the child. A 20 kg five-year-old on a 12 kg bike is riding sixty per cent of their own body weight. Scale that to an adult of 75 kg and it is a 45 kg bicycle.

Nobody would expect an adult to enjoy learning on a 45 kg bike, or to lift it onto a kerb, or to pick it up after stopping. Children are asked to do exactly that constantly, and then described as not being interested in cycling.

• Under 30 per cent of the child's weight: genuinely good. The child can lift, lean and correct the bike freely.
• 30 to 40 per cent: workable. Most decent bikes land here.
• 40 to 50 per cent: hard work, especially uphill or when starting from a stop.
• Over 50 per cent: the bike is the main obstacle to learning, whatever else it has.

Where the weight actually is

Steel frames account for some of it, but the bulk usually comes from parts that add nothing at this size. A suspension fork on a 16 inch bike can weigh 1.5 kg and does nothing useful at the speeds a child rides. Steel wheels, steel cranks, oversized tyres and a chainguard the thickness of a saucepan lid make up most of the rest.

Weight in the wheels matters roughly twice as much as weight in the frame, because it has to be accelerated rotationally as well as carried. A bike with aluminium rims and lighter tyres feels dramatically easier than its total weight suggests.

Gears, honestly

Below about 20 inch wheels, gears are close to useless. A young child rides on flat ground at walking pace, and the mental load of managing a shifter competes directly with steering, balancing and watching where they are going.

A single gear also means no derailleur to bend, no shifter cable to seize and one fewer thing that stops working after a winter in a hallway. Single speed is the right answer for most first and second bikes.

From 24 inch upward, on a child riding real distances or real hills, gears start to earn their place. Even then, a simple six or seven speed setup is easier to learn on than a wide-range double.

What to spend money on instead

• Lighter wheels and tyres, which change how the bike feels more than anything else.
• Short-reach brake levers a child can actually pull.
• A frame with a low standover, so the child can put both feet down easily.
• Nothing else. No suspension, no gears, no accessories until the bike is being ridden regularly.

The second-hand advantage

A three-year-old specialist bike is usually lighter, better made and cheaper than a new supermarket one, because children outgrow bikes long before they wear them out. Buying used is the most reliable way to get the weight down without spending more.