A proper guide to choosing a child's bicycle — with criteria, tables and a recommendation for every case — is too big a subject, and I am not attempting it. Instead: what I bought and built, what to steer clear of, and what I look at when putting a bike together.

What to avoid

"Mag" wheels with blades instead of spokes

A firm no. Wheels like that come in two kinds. The first is the narrowly specialised racing sort, bought by very few people and costing thousands or even tens of thousands of dollars (as of 2026). The second, far more likely, is junk built to look cool.

What is wrong with them:

  • they cannot be repaired;
  • they weigh an incredible amount;
  • as a rule the rest of that bicycle is also built to be looked at rather than used — and it works very badly indeed, even next to the lowest-tier parts from real manufacturers.

Coaster brakes

Hand brakes only. A coaster brake adds around half a kilogram, does not work if the chain comes off or jams, needs the child to be able to pedal backwards — and they will have to learn hand brakes anyway, so better sooner.

Mechanical disc brakes

For children they seem to me less effective than even good rim brakes, while weighing as much as hydraulic discs. And hydraulics like the Shimano MT200 have become more than affordable — paying for mechanical brakes in weight makes no sense to me.

The first bicycle

For both of my children I bought the Decathlon B'Twin 500 on 14-inch wheels. Why that one:

  • it is cheap;
  • the ergonomics are sensibly thought through;
  • it is simple — there is nothing in it to break;
  • you do not have to protect it. That matters more than it sounds: a small child does not yet grasp that "this bike is expensive, look after it" — they are simply happy, having fun, getting on with life. A cheap bike spares the child the "we bought you a good bicycle and you leave it lying anywhere" conversation, and spares the parents the nerves;
  • the gearing is low: the child can climb almost anything, and cannot pick up enough speed downhill to kill themselves.

After that it becomes clear what bike the child actually needs.

Next: 20 and 24 inches

My children took to cycling — not passionately, but they took to it. So I built them bikes on 20-inch wheels, and from there they move up to 24.

Why not 16: I simply could not find a 16-inch frame that takes gears.

What I looked at when building

Not in order of importance — in the order it came to mind.

A rigid fork, no suspension

Some people no less experienced than me, often considerably more, fit suspension to their children's bikes. My feeling is that it will not really work under a 25 kg child — and I do not mean the cheap sprung forks that do not work at all, but expensive forks and shocks at several hundred dollars each (as of 2026).

Brakes

Hydraulic disc at the front. At the rear it does not matter much: hydraulic disc or mechanical rim.

We live next to the mountains, and in my experience children's fingers tire from holding the brake on a descent: every 100 metres of descent you have to stop and let the fingers rest.

A front brake is mandatory. Effective braking is mostly the front wheel, bar some very specific cases. If someone went over the bars as a child and has removed the front brake ever since, the cure is not taking the brake off but learning to shift your weight back as you brake. Learn it yourself, and teach the child.

Suspension comes from the tyres

Fat tyres at low pressure. Work it out yourself: if you ride at even 2 bar, then in proportion to the child's weight and the rim diameter, how much do they need? The number will surprise you. I run 0.6–0.9 bar, no more.

In winter, an electronic groupset

Children have small fingers, and shifting in mittens is very awkward — even on top-tier components like X.0 or XTR. Electronics take that problem away.

If you already have a decent groupset, you can simply replace it with an LTWOO AE. Here is the only problem I have run into in three years of using it.

Fit, and the Q factor

The Q factor is the distance between the pedals, and for children it matters especially. Checking it is easy: measure the distance between the pedals on the child's bike, scale it up in proportion to the length of your own legs — and try pedalling like that. If the pedals sit too wide apart, it is very uncomfortable to ride.

A narrow Q factor is often called a mark of expensive children's bikes. It is an indirect one: a narrow bottom bracket can be fitted to a cheap bike just as well.

A helmet

Do not forget it. Even if you are not planning anything extreme with the children — are you sure the child has no other plans? Or not even plans: they simply spot someone and decide to race, while you are still opening your mouth to say "hey, where are you going". Unless, of course, you keep a spare child.

One trick for everything else

Geometry, fit, bar width, the weight of the bike and so on — all of it is answered by one thought experiment: imagine you are riding this bicycle, only scaled up to your own size, every dimension at once. It settles a great many "should it really be like that?" questions.

And the general rule that follows from it: pick the bike for the child's height now, not for the height they will grow into.

If the child is not riding yet, start here: how to teach a child to ride a bicycle.