Most second-hand bikes are fine. Some are not, and the difference is usually easy to spot once you know where to look.

You do not need tools and you do not need to know much about bikes. Ten minutes in someone’s driveway is enough. Here is what I look at.

Wheels. Spin them. Watch for side to side wobble.
Brakes. They should bite well before the lever hits the bar.
Chain and gears. Every gear should engage within a second.
Frame. The only fault you cannot put right.
Tyres. Cracked sidewalls mean the rubber has perished.
Does it fit you. Both feet down, and no rocking to reach the pedals.

The six things worth looking at, in the order they are covered below. Only one of them, the frame, is a reason to walk away on its own.

How can you tell if a used bike is any good?

Lift the bike a few inches and drop it. Listen for rattles. Spin both wheels and watch the rim pass the brake pads. It should stay in one place, not wobble side to side. Squeeze both brakes and push the bike forward; it should not move. Those three checks catch most bad bikes in under a minute.

If all three are fine, the bike is probably worth looking at properly. If one of them is wrong, keep reading, because some problems are cheap and some are not.

Do the wheels spin straight?

Spin each wheel and watch a fixed point, like the brake pad. A wheel that moves side to side as it turns is buckled. A small wobble can usually be trued; a big one, or a kink you can see, means the wheel is bent and may need replacing.

Then hold the top of the wheel and push it sideways. If it rocks, the bearings are worn. That is a repair, not a disaster, but it is a reason to offer less.

Squeeze pairs of spokes together all the way round. They should feel about the same. A loose one is fine. Several loose ones means the wheel has not been looked after.

Do the brakes actually stop it?

Pull each brake lever. It should stop firm, well before it touches the handlebar. Look at the brake pads: if the grooves in the rubber have worn away, they need replacing. Then push the bike forward with the brakes held on. The wheels should not turn at all.

Brake pads are cheap and easy to change. Cables are cheap too. So bad brakes on an otherwise good bike are not a reason to walk away, but they are a reason not to ride it home.

If it has disc brakes, look at the disc itself. It should be flat. Run a finger near it, not on it, and look for deep scoring.

What about the chain and gears?

Lift the back wheel and turn the pedals. The chain should run smoothly and quietly. Change through every gear. Each one should engage within a second and stay there. A chain that jumps on its own, or clicks constantly, needs adjusting at best and replacing at worst.

A chain rusted solid is bad news. Not because chains are expensive, they are not, but because it tells you the bike has been outside all winter, and everything else will have suffered too.

Pull the chain away from the front of the big chainring. If you can pull it far enough to see daylight under it, the chain is stretched and has probably worn the teeth down with it.

Is the frame sound?

This is the one thing that genuinely matters, because a cracked frame cannot be fixed and a bike with one is not safe at any price.

Look along the whole frame in good light, especially where the tubes meet. You are looking for cracks, dents, ripples in the paint, or anywhere the metal looks folded. Pay most attention to the tube behind the front forks. That is where a bike that has been hit from the front gives itself away.

Surface rust on steel is normal and mostly cosmetic. Rust that has eaten into the metal, or bubbled the paint up from underneath, is not.

How are the tyres?

Look at the tread and the sidewalls. Cracks in the sidewall mean the rubber has perished and the tyre should be replaced whatever the tread looks like. Press a thumb in: it should feel firm. Tyres are one of the cheapest things on a bike to put right.

Do not let a seller tell you flat tyres mean the bike is broken, and do not let them knock much off for it either. A pair of tyres and tubes costs less than most people think.

Does it fit you?

Stand over the frame with both feet flat on the ground. On a normal bike you want two or three inches between you and the crossbar. Then sit on the saddle and put a heel on the pedal at its lowest point. Your leg should be almost straight. If you have to rock your hips to reach, the bike is too big.

A bike that does not fit will not get ridden, however good it is. This is the most common mistake I see, and it is the one people notice last.

What if you cannot tell?

Take someone who knows bikes. If you cannot, ask the seller to let you ride it somewhere quiet, round a car park, not just up and down outside the house. Most problems show themselves in the first two minutes of actually riding.

And if the seller will not let you ride it, that is your answer.

The short version

Drop it, spin the wheels, squeeze the brakes
Frame cracks are the only thing you cannot fix
Brakes, tyres, chains and cables are all cheap
If it does not fit, nothing else matters
Ride it before you pay

Going the other way, and trying to get rid of one? We have written about what to do with an old bike you don’t use, including why the tip beats the council for it.

Worth knowing before you hand over money: buying privately gives you no consumer rights at all, which is one of the things we cover in are cheap second-hand bikes safe?

If you would rather somebody had already done all of that, it is what we do to every bike before we sell it.

What to check before you buy a used bike