Bike Fit for Kids: Getting Their Setup Right

Rather than guessing, measure your actual position with your own camera.

€5 for one fit, or 10 fits for €25. See pricing →

The advice that causes the problem

Almost every parent is told the child should be able to put both feet flat on the ground while seated. For a balance bike or a child just learning, that is reasonable: they need to catch themselves.

But once a child can ride confidently, keeping that rule means the saddle stays far too low. A low saddle over-bends the knee at the top of every pedal stroke, which is exactly the position that causes front-of-knee pain, in children just as in adults. It also makes pedalling much harder work, which is often mistaken for the child being unfit or unwilling.

What to aim for instead

Once a child rides confidently and can start and stop reliably:

• With the ball of the foot on the pedal at the bottom of the stroke, the leg should be almost but not quite straight, a slight bend at the knee, the same target as an adult.
• Seated on the saddle, they should be able to touch the ground with their toes, not flat feet.
• If they are nervous about this, raise the saddle gradually over several weeks rather than in one jump. Confidence matters more than getting there quickly.

For a child still learning to start and stop, keep the saddle lower and accept the inefficiency, safety and confidence come first. The height can rise as the skill arrives.

Check every few months, not every year

This is the part most parents miss. Children grow in bursts. A saddle set correctly in spring can be significantly too low by autumn, and the child will not usually say anything, they simply adapt, and pedal with a bent knee.

Recheck saddle height every two to three months, and after any growth spurt. It takes two minutes and prevents the knee pain that gets blamed on "growing pains".

Reach and bar height

Children are often placed on bikes that are too long for them, because a bike they can "grow into" seems economical. A bike that is too long forces them to stretch, which makes the steering twitchy and the bike harder to control, a genuine safety issue, not just comfort.

• The child should reach the bars with a slight bend in the elbows, not stretched out.
• They should be able to reach and operate the brake levers comfortably with the hand they actually have. Most children's brake levers have a reach adjustment; use it. A child who cannot brake firmly is riding an unsafe bike.

Bike weight matters more than for adults

A typical children's bike weighs a large fraction of what the child weighs. Handling a heavy bike at low speed is disproportionately hard for them, and it affects their position: a bike they cannot control makes them tense and stiff-armed.

If you have a choice, weight is one of the more useful things to spend money on for a child's bike.

Signs the setup is wrong

• Knees splaying out to the sides while pedalling, or coming close to the handlebars: the saddle is too low.
• Rocking hips: the saddle is too high, which happens after a growth spurt is over-corrected.
• Complaining of knee pain: check saddle height first, before assuming it is growing pains.
• Reluctance to ride, or tiring very quickly: often a saddle so low that pedalling is genuinely exhausting.

A note on pain in growing children

Children do get genuine growth-related knee complaints, and some conditions specific to growing bones cause knee pain around the same ages that children start riding more. If a child's knee pain persists after you have corrected the saddle height, is severe, involves swelling, or occurs off the bike as well, see a doctor rather than continuing to adjust the bike. This is one area where getting it checked is clearly the right call.

Measuring rather than guessing

The same knee-angle logic applies to a child as to an adult, which means it can be measured the same way. A BikeFit/LAB analysis works from a short side-view video of them pedalling and reports the knee extension angle against the target range, useful precisely because children rarely articulate that something feels wrong, and because it gives you a number to compare against at the next growth spurt.

Rather than guessing, measure your actual position with your own camera.

€5 for one fit, or 10 fits for €25. See pricing →