How to Fix a Flat Tire

This is the one repair every cyclist needs. It takes about ten minutes once you have done it twice, and the difference between knowing it and not is the difference between a short stop and a long walk.

Practice it once at home before you need it in the rain. That single dry run is worth more than reading this page twice.

What you need with you

• A spare inner tube in the correct size for your tires — the size is printed on the tire sidewall.
• Two or three tire levers. You cannot get a tire off with fingers alone.
• A pump or CO2 inflator.

About $35 total. Keep it in a saddle bag permanently so it stops being a decision you can get wrong.

The eleven steps

1. Get off the road. Completely off. Everything else can wait until you are somewhere safe with space to work.
2. Shift to the smallest rear sprocket before removing a rear wheel. It moves the chain out of the way and makes refitting far easier.
3. Release the brake if needed and open the quick-release or thru-axle. Take the wheel off.
4. Let out any remaining air and push the tire bead into the center channel of the rim all the way round. The rim is deeper in the middle, and this slack is what makes the tire come off easily. Skipping this is why people struggle.
5. Hook one lever under the bead and clip it to a spoke. Insert the second lever a few inches away and slide it around to free one side of the tire. Leave the other side on the rim.
6. Pull the old tube out, starting away from the valve and removing the valve last.
7. Find the cause. The step everyone skips. Run a finger slowly around the inside of the tire — carefully, because whatever caused it may still be in there. Also check the rim tape covering the spoke holes. If you can match the hole in the tube to its position on the tire, you know exactly where to look.
8. Put just enough air in the new tube to give it shape. A completely flat tube twists and gets pinched; an over-inflated one will not fit.
9. Fit the valve through the rim hole first, straight rather than at an angle, then feed the rest of the tube inside the tire all the way round.
10. Work the tire bead back on with your thumbs, starting at the valve and working both directions. Keep pushing the bead into the center channel as you go. The last section is the hardest — avoid levers here if you possibly can, because levering is how the new tube gets pinched.
11. Check, then inflate. Push the valve up into the tire and pull it back down to make sure the tube is not trapped under the bead. Work round both sides checking no tube is showing. Then inflate to your usual pressure.

The three mistakes that cause a second flat

1. Not finding what caused it

If a thorn is still embedded in the tire, it punctures the new tube within a mile. This is far and away the most common reason for a repeat, and step seven exists solely to prevent it.

2. Pinching the new tube

Trapping the tube under the bead while fitting the tire gives you a flat as soon as you inflate. Prevented by putting a little air in the tube first, and by using thumbs rather than levers on the final section.

3. Riding away at too low a pressure

Especially after using a mini pump, which takes a lot of strokes and tempts you to stop early. Under-inflation is the leading cause of pinch flats. Re-inflate properly with a floor pump when you get home — and note that CO2 leaks out of a tube faster than air does, so a CO2-inflated tire will be soft by the next morning.

If you have run out of spare tubes

Two field repairs worth knowing:

A tire boot. If the tire itself has a cut large enough for the tube to bulge through, no tube will survive. Put something firm between the tube and the cut — a folded energy bar wrapper or a banknote both work — to bridge the hole. It is a get-home fix, not a repair, and the tire needs replacing.

A patch. Roughen the area, apply glue, wait until it is tacky rather than wet, then press the patch on firmly. The waiting is the part people rush and it is the part that makes it hold.

How to get fewer punctures

• Run correct pressure. The single biggest factor, and free.
• Buy tires with sidewall protection. The Maxxis Rambler on our tire page is the one that publishes a named protection layer.
• Replace tires when the tread is thin. Repeated punctures in a tire that used to be reliable is the tire telling you it is finished.
• Avoid the gutter on roads, where glass and debris collect.