20" Bikes
Browse used 20in bikes for sale from riders across the UK. A 20in wheel suits an inside leg of roughly 51-60cm and ages six to eight, and this is where gears arrive — usually a 1x drivetrain with six to nine sprockets and a single chainring. It suits children moving from riding round the park to keeping up on family rides and easy trails.
Is a 20in kids' bike the same as a BMX?
They share a wheel size and nothing else. A BMX has a short, strong frame, a high bottom bracket, one gear and a rear brake only, all built for jumps and skateparks, and it is sized by top-tube length rather than by the rider's inside leg. A 20in kids' bike has a long, low frame, gears, two brakes and a saddle set for pedalling efficiency. A child who wants to ride to school and up hills needs the latter, even if the wheels look identical in a listing photo.
How many gears does a 20in bike need?
A single chainring with a wide-range cassette is the usual arrangement and is all that is needed — front derailleurs add weight and give children two shifters to confuse. Look for a trigger shifter rather than a twist grip, since twist shifters need a firm grip that small hands often lack when tired. If a bike has a suspension fork, weigh it up carefully: a cheap coil fork at this size adds 1-2kg, rarely moves under a 25kg rider, and does nothing except make the bike harder to pedal.
What should I check on a used 20in bike?
Shift through every gear with the bike off the ground; sticky or skipping shifts usually mean rusted inner cables or a bent mech hanger from the bike being dropped on its drive side, both cheap to fix but worth knowing about. Check the chain for stretch and the sprocket teeth for hooking, since this is the first size where children put in enough miles to wear a drivetrain out. Look for reach-adjustable brake levers, check rim brake pads and the rim sidewall, or the rotor and pad thickness on a disc bike, and make sure the seatpost is not seized and has enough length left to grow into.
Should I size up to 24in instead?
Only if the child is at the top of the height range now. A 20in that fits is far more use than a 24in they can barely stand over, and confidence at this age comes from being able to stop and put a foot down without thinking. The kids' complete bikes listings are grouped by wheel size so you can compare the same bike across two sizes, and a younger sibling's 12in bike or balance bike can often be bought in the same trip.
What should I pay for a used 20in bike?
Expect to pay around half of retail for a well-kept geared bike from a lightweight brand and considerably less for a heavy one with a dead suspension fork. Buy new if you need a specific frame size for a child on the cusp and want the warranty on hydraulic brakes; otherwise a used bike plus a fresh chain and tyres will be better value and can be sold on for close to what you paid.