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How to fix a bicycle puncture

Before you fit a new or patched tube, find what caused the puncture and remove it. A thorn or chip of glass left in the tyre will puncture the new tube within minutes.

What you need

• two tyre levers;
• a patch kit or a spare tube that matches your tyre size and valve type;
• a pump that fits your valve.

Step by step

1. Remove the wheel. Open the brake if you need to. For the rear wheel, shift to the smallest sprocket first.
2. Loosen the tyre. Let out any remaining air and push the edges of the tyre into the deep centre of the rim, all the way round.
3. Lever one side off. Hook a lever under the edge of the tyre opposite the valve and clip it to a spoke. Put in a second lever a little further along and slide it round the rim.
4. Pull out the tube, valve last.
5. Find the hole. Pump some air in and listen for a hiss, or feel for air on your cheek. If you cannot find it, hold the tube under water and watch for bubbles. Mark the hole.
6. Find the cause. Run your fingers slowly and carefully round the inside of the tyre. Remove any thorn, glass or wire, and check the rim tape.
7. Patch the tube. Roughen the area with the sandpaper from the kit. Spread a thin layer of glue a little larger than the patch and wait until it is dry to the touch. Press the patch on firmly from the centre outwards for a minute.
8. Refit. Put a little air in the tube so that it holds its shape. Put the valve through the rim, tuck the tube into the tyre, and push the tyre back onto the rim by hand, starting at the valve. Avoid levers here, because they can pinch the tube.
9. Pump and check. Pump a little and check that the tube is not caught under the tyre anywhere. Then pump to the right pressure, refit the wheel and check the brakes.

What the hole tells you

• One small hole on the outside: a thorn, glass or wire in the tyre at that point.
• Two small slits side by side: a pinch flat, from low pressure or a hard knock.
• A hole on the rim side: a sharp spoke end or damaged rim tape.
• A split at the seam or the valve: often low pressure or an old tube.

Repeated punctures in the same place mean that the cause is still in the tyre.

Patch or replace?

Replace the tube if it has many patches, a hole near the valve, a long split or cracked rubber. Replace the tyre if the tread is worn flat, the threads show, the sidewall is cracked, or there is a bulge or a cut large enough for the tube to push through.

Preventing punctures

• Keep the tyres at the pressure range printed on the sidewall, and check weekly with a gauge. Tyres lose air slowly even without a puncture.
• Avoid glass and thorny verges. In many parts of South Africa, small hard thorns such as the duwweltjie are a common cause.
• Pick out anything stuck in the tread after a ride.
• For thorny routes, consider thorn-resistant tubes, tyre liners or sealant.

Carry a spare tube or patches, two levers and a small pump on every ride.

This guide is based on Chapter 4 of Bicycle Maintenance and Repair, which also explains tyre sizes, valves and fitting new tyres.