How to fix a flat tyre

What to carry

A roadside repair goes smoothly or badly depending almost entirely on what is in your saddle bag. The short list: a spare tube in the right size, two tyre levers, a pump, a multitool with the right hex keys, and a patch kit as a backup for a second puncture. If your bike has bolt-on wheels rather than quick releases, make sure the multitool actually fits those nuts.

Add a pair of disposable gloves if you commute in decent clothes, and a small piece of old tyre or a banknote-sized bit of plastic to boot a cut casing. None of it weighs much and all of it saves a long walk.

Getting the wheel and tyre off

Move off the road first. Shift to the smallest sprocket if the rear wheel is the flat one, as this makes it far easier to get the wheel out and back in. Open the brake if it is a rim brake, release the quick release or undo the thru-axle, and lift the wheel out.

Let out any remaining air. Push the tyre bead towards the centre of the rim all the way round — the rim channel is deeper there and this slack is what makes the tyre come off easily. Hook one lever under the bead, then a second lever a hand's width along, and run it round. Pull the tube out, leaving the valve until last.

Find the cause

This is the step people skip and then regret ten minutes later. Something caused the flat and it is often still in the tyre. Run your fingers carefully around the inside of the casing — carefully, because glass and wire will cut you — and look at the outside of the tread in good light.

Inflate the old tube slightly to find the hole, then line it up with the tyre to work out where the damage sits. Two small holes side by side, like a snake bite, means a pinch flat from running too little pressure or hitting an edge hard. A single clean hole usually means a thorn, and in much of South Africa that thorn is a devil thorn, which loves gravel shoulders. A tear on the sidewall means the casing itself is damaged and needs a boot behind it.

Check the rim tape as well. If it has slipped and exposed a spoke hole, your next tube will puncture in the same spot within a kilometre.

Fitting the tube

Put a little air into the new tube, just enough to give it shape. This stops it folding over on itself and getting pinched. Seat the valve through the rim hole first, then feed the tube into the tyre all the way round.

Work the bead back onto the rim with your thumbs, starting opposite the valve and finishing at it. Avoid levers on the way back on if you possibly can: this is the single most common way to pinch and puncture a brand new tube. If the last section is stubborn, push the rest of the bead deep into the rim channel to free up slack.

Before adding pressure, go round the wheel on both sides and check that no tube is peeking out between bead and rim, and that the moulded line on the tyre sits an even distance from the rim all the way round.

Reinflating properly

Inflate slowly at first and watch the bead seat evenly. Stop at the pressure that suits your tyre and your weight rather than pumping until it feels hard — see the tyre pressure guide for typical starting ranges, and always stay inside the range printed on the sidewall.

This is where a gauge earns its place. The Freewheel Pocket Pump shows pressure on a digital display and stops by itself at the figure you set, so you can finish a roadside repair at the same pressure you would have chosen at home. It fits Presta and Schrader valves. On a Presta valve, remember to close the lock nut afterwards.

Refit the wheel, close the quick release or torque the axle properly, close the brake, and spin the wheel to check it runs true and clear. Then pack your old tube — never leave it on the verge — and get going.

A note on tubeless

On a tubeless setup, small punctures often seal themselves as sealant rushes into the hole. Keep riding gently for a few seconds and rotate the hole to the bottom to help it. For a larger hole, a tubeless plug pushed into the cut is usually enough to get home. If the tyre will not hold air at all, fit a tube: pull out the valve stem, remove the tyre, wipe out what sealant you can, and proceed exactly as above.

Fewer flats next time

Most punctures are preventable. Keep your pressure in the right range, because soft tyres pinch and hard tyres cut. Replace tyres when the tread is worn through or the casing is nicked. Pick your line to avoid the gutter of thorns and glass on the road edge. If you keep picking up thorns on gravel, consider a tyre with a puncture-resistant belt or going tubeless with fresh sealant.

And check your pressure before every meaningful ride. It takes under a minute and it is the cheapest reliability upgrade there is.