Flats are an unavoidable part of cycling. Here’s how to repair a punctured tube or fit a new one.
Clean bike and wheels
Give your bike a good clean before attempting to fix the puncture. Pay particular attention to the wheel with the flat tyre, making sure you get rid of all the muck. Give the bike a quick wipe down to dry it, then either clamp it in a workstand or flip it upside-down.
Inspect for damage
Rotate the wheel in the frame/fork and inspect the tyre for damage. If you find any, note where it is in relation to the tyre. Remove the wheel, replacing the axle in the frame/fork. Deflate the tube by pressing the valve core down with a 3mm Allen key (Schrader/car type valve) or turning it anticlockwise and pressing it down with your finger (Presta valve).
Push bead from rim
Facing the wheel side on, rotate it, pushing the closest bead (lower edge) of the tyre into the center of the rim bed with your fingers as you go. Hook a tyre lever over the rim and under the bead and use it to lever the tyre upwards and over the sidewall of the rim. Then hook the looped end of the lever over the closest spoke. Position a second tyre lever 50mm from the first.
Remove tyre and tube
Unhook the first lever and reposition it 50mm further on from the second lever. Continue working your way around the wheel, one lever at a time, until one side of the tyre is completely removed from the rim and you can see the inner tube. Find the inner tube valve and pop it out of the rim and tyre. Remove the rest of the tube from the tyre.
Check inside tyre
Slowly run your hand around the inside of the tyre, checking for anything that could have penetrated it and caused the puncture. If you come across a thorn or other item of trail debris, use needle-nose pliers to carefully pry it out, making sure there’s nothing left stuck in the rubber that could cause another flat. Once removed, continue to check the rest of the tyre.
Check tube for damage
It’s now time to inspect the damage to the inner tube and assess whether or not it’s repairable. If you plan on fitting a new tube regardless, skip to step 13. Otherwise, inflate the inner tube, ideally using a track pump. Once inflated, you should be able to spot the hole in the tube. If you can’t see the hole, hold the tube close to your face and feel/listen for leaking air.
If you still can’t locate the hole, fill a bowl with water and slowly pass the tube through it. The leaking air will create bubbles, making the hole easy to spot. If there are two large, parallel holes – known as a ‘pinch flat’ or ‘snakebite’ – it’s easier just to fit a new tube. If there’s a single hole less than 2mm wide, it should be easy to fix.
Draw an ‘X’ over the hole with a marker pen to make it easy to locate. Then use the sandpaper from your puncture repair kit to lightly roughen up the affected area. It’s worth sanding an area that’s a little bigger than the patch you’re going to use for the repair. Make sure you don’t roughen up the tube so much that you wear off your mark though.
Apply glue to tube
Coat the sandpapered area with glue from your puncture repair kit. A thin, even coating is all you need. Hang the tube somewhere dust-free to wait for the glue to become tacky (not dry!). This should only take a minute or two. While waiting, pick a suitably sized repair patch and remove the foil backing, leaving the paper covering on the opposite side attached.
Fix patch to tube
With the glue now tacky/sticky, place the patch centrally over the mark you made on the tube, ensuring you cover the hole completely. Make sure it’s stuck down evenly, using the rounded back of one of the tyre levers to press it down, working from the centre of the patch outwards to the edges. Now it’s time to remove the paper patch backing.
Check patch is secure
Hold the tube between your thumbs and forefingers, with your thumbs on the paper patch backing. Pull your thumbs away from each other to create a tear in the paper backing. Peel the torn paper backing off the patch from the center outwards, making sure the patch stays stuck firmly in place.
Rub with chalk
Attach your pump and partially inflate the tube. Dunk the patched area in the washing-up bowl full of water and watch for bubbles. If there aren’t any, the tube is ready to be fitted. Remove it from the water and dry it. Grate some chalk from the repair kit all over and around the patched area of tube to prevent it sticking to the inside of the tyre.
Check the tyre for debris one last time. Slot the valve stem of the tube back through the valve hole in the rim bed and sit the tube back inside the tyre. Starting opposite the valve, use both hands to fold the tyre bead over and into the rim. Work your way around the rim, moving your hands in opposite directions and making sure not to pinch the tube in the process.
You may find there’s a small section of tyre near the valve stem where the bead is too tight to seat by hand. If so, hold one end of the unseated section of bead in place with your hand (to prevent it coming out of the rim further) and at the other end of the unseated section. Use a tyre lever to hook the bead into the rim, being careful not to pinch the tube.
When the tyre is back on the rim, double check the valve area to ensure the bead is correctly seated. You may need to manipulate the valve gently until the bead sits snuggly around it. Working your way around the tyre, push the bead into the center of the rim. Then attach your pump to begin inflating the tube.
Keep a careful eye on the tyre bead as you’re adding pressure to make sure it’s seating evenly and not bulging anywhere. Once the tyre is at your desired pressure, do another visual check to make sure the bead is correctly in place before fitting the wheel back on your bike.