Checking a second-hand children's bike in ten minutes

Children's bikes are the best second-hand buy in cycling. Most are ridden for a season or two by a child too light to wear anything out, then stored. The result is a market full of nearly-new bikes at a third of the price, mixed in with a few that are genuinely finished.

Before you go

Ask for the wheel size and, if the seller can manage it, the minimum saddle height and the weight. Ask whether it has been stored indoors or outdoors, because a bike left in a garden for two winters is a different proposition to the same bike kept in a hallway.

Take a tape measure, a hex key set and your child if practical. Trying it is worth more than any photograph.

The eight checks

1. Frame. Look along the top tube and down tube for dents, and around every weld for cracks or rippled paint. Surface rust is cosmetic; a dent with a crease in it is not, and that bike is finished.
2. Wheels. Spin each one and watch the gap at the brake pad. A small wobble can be trued; a wheel that rubs the frame each turn or has loose spokes you can rattle by hand is a repair.
3. Bearings. Hold the wheel and rock it side to side. Movement means the hub bearings are loose, which is adjustable but should come off the price. Do the same with the cranks and the handlebars.
4. Chain and sprockets. A chain that lifts noticeably off the front sprocket when you pull it is worn, and on a child's bike that is usually a sign of outdoor storage rather than mileage.
5. Brakes. Squeeze both levers. The blade should stop well short of the grip with the pads gripping firmly. Look at the pads themselves for grooves worn past the pattern.
6. Tyres. Check the sidewalls for cracks. Perished rubber on a stored bike is common and cheap to replace, but factor it in.
7. Saddle height. Push the seatpost all the way down and measure to the top of the saddle. This is the number that decides whether the bike fits, and it is the one nobody advertises.
8. Weight. Lift it. If it feels heavy to you, it is unmanageable for the child.

What is worth fixing

Cables, brake pads, tyres, tubes, grips and a saddle are all cheap and easy, and a bike needing all of them is still often a good buy if the frame and wheels are sound. Budget for a set of cables and pads on anything stored outdoors.

Bearings, if loose rather than rough, are an adjustment rather than a replacement on most children's bikes. Rough or gritty bearings are a bigger job and usually mean water got in.

The one thing not to buy used

A helmet. The foam compresses permanently in an impact and there is no way to see whether that has happened, so a used one may look perfect and no longer do its job. Everything else on this list is fine second-hand.

Price sense

A well-known specialist brand three or four years old typically sells for a third to a half of new, and is still lighter and better than a new budget bike at the same price. A supermarket bike of any age is worth very little, because the thing that made it cheap new is still true.

The best time to buy is late autumn and winter, when nobody is thinking about bikes. The worst is the first warm weekend of spring, when every listing has six people waiting.