5 Things to Check Before Buying a Second-Hand Bike

You've found a bike that looks perfect. The price is right. The photos look good. Before you hand over any money, run through these five checks. They take five minutes and could save you hundreds, or keep you safe.

1. Check the Frame Number

This is non-negotiable. Every bike has a serial number, usually stamped under the bottom bracket shell.

Why it matters: It's the only reliable way to check if a bike is stolen. Cross-reference it with BikeRegister and your local police database.

Red flag: The seller can't find the serial number, or the area where it should be stamped looks filed or altered.

2. Inspect the Frame for Damage

Run your hands over the frame, especially around:

• Head tube, where the fork meets the frame. This takes the most crash force.
• Down tube / seat tube junction, common stress point.
• Chainstays, look for cracks near the dropout.
• Underneath the bottom bracket, stone chips are fine; cracks are not.

For carbon frames: Tap gently with a coin. A dull thud (instead of a clear ring) can indicate delamination. Be especially thorough around any areas with paint touch-ups, they may be hiding damage.

For aluminium frames: Look for wrinkles, dents, or bulges. Aluminium doesn't give warning before it fails.

3. Check the Drivetrain

The drivetrain (chain, cassette, chainrings) is the most expensive wear item on a bike.

Quick chain check: If you don't have a chain checker, pull the chain away from the front chainring at the 3 o'clock position. If you can see daylight between the chain and the ring, the chain is worn.

Cassette check: Look at the teeth. They should be symmetrical. Shark-finned teeth (hooked to one side) mean the cassette needs replacing.

Cost implication: A full drivetrain replacement (chain + cassette + chainrings) costs £100-300 depending on the groupset. Factor this into your offer price.

4. Spin the Wheels

Lift each wheel off the ground and spin it. Watch the gap between the rim and the brake pad (or fork, if disc brakes):

• Lateral wobble (side to side): A slight wobble can be trued cheaply (£15-25). A big wobble may mean a bent rim.
• Radial wobble (up and down hop): This usually means a damaged rim and is more expensive to fix.

Also squeeze pairs of spokes, they should feel evenly tensioned. One floppy spoke means the wheel needs attention.

5. Test the Bearings

Three bearing sets to check:

Headset: Turn the handlebars slowly with the front wheel off the ground. Any notchiness, grinding, or resistance means the headset bearings need replacing (£20-50 for parts, plus fitting).

Bottom bracket: Rock the cranks side to side. Any play (clicking or movement) means the bottom bracket is worn. Replacement cost varies wildly: £30 for a basic BSA to £100+ for a press-fit.

Wheel hubs: Grab each wheel at the top and rock it side to side. Any clunking means the hub bearings need adjustment or replacement.

The Five-Minute Rule

All five checks take about five minutes. If the seller is rushing you or doesn't want you to inspect the bike properly, that tells you something.

A good seller will welcome your inspection, they know their bike is sound and want you to feel confident. A bad seller will make excuses.

Trust your gut. And if you want data to back it up, check what similar bikes in similar condition have sold for on Cyclesite's sold prices page.