Flat tyre on a wheel with an inner tube

The tyre is flat or almost flat and the wheel has an inner tube (most spoked commuter wheels). The steering goes heavy or the rear slides and wobbles. A tube can be patched or replaced, but the cause must be found or it will go flat again.

Is it safe to ride?

No. Stop as soon as it is safe. Riding on a flat tube tyre destroys the tube and tyre within metres, can damage the rim, and a flat front can make you crash. Push the bike to a fundi or repair it where you are.

Quick checks first

• Stop off the road, put the bike on its stand.
• Look round the tyre for a nail, glass, wire or thorn. Mark it with chalk.
• Look at the valve: is it straight or leaning?
• Did you hit a pothole or kerb just before? (Pinch puncture.)

Diagnose it step by step

1Pump the tyre. Does it hold air for a few minutes?

• Yes: it is a slow leak. If you must move the bike, ride very slowly to the nearest repair point and recheck often. Then see Tyre slowly loses air.
• No: remove the tube. Follow Repair a puncture in an inner tube. Go to step 2 when the tube is out.

2Pump a little air into the tube and find the hole (listen, or use water). Where is it, and what does it look like?

• One small hole on the outer (tread) side: an object. Go to step 3.
• Two small slits side by side ("snake bite"): the tube was pinched between tyre and rim, usually from low pressure or a hard hit. Patch both, check the rim for a dent, then keep pressure correct (Check tyre pressure).
• Hole on the inner (rim) side: go to step 4.
• Tear at the valve base: the tube crept on the rim, usually from low pressure. Fit a new tube (Check and replace a tyre valve).
• Long split or many holes: the tube is finished. Fit a new tube and go to step 5.

3Lay the tube on the tyre with the valve at the valve mark. Is there an object in the tyre at the matching place?

• Yes: remove it from inside and outside. Patch or replace the tube.
• No: feel carefully round the whole inside of the tyre with gloves. Small wire pieces hide well.

4Look inside the rim. Does a spoke end stick out, or is the rim tape torn or out of place?

• Yes: file the spoke end flat, fit new rim tape. Check the spokes (Check and tighten spokes).
• No: look for a sharp burr at the valve hole or a rim crack (Rim is dented or cracked).

5Look at the tyre inside and out. Is there a cut through the cords, a bulge or broken threads inside?

• Yes: the tyre must be replaced (Replace a tyre). A new tube in a cut tyre will fail.
• No: fit the new or patched tube, inflate, and check pressure again the next day.

Causes, most likely first