Knowing how to repair a punctured inner tube is an essential skill that every cyclist needs to master. It can be daunting for the inexperienced but only takes a few minutes once you know what you're doing. If you flat on the road or on the trail, it's faster to simply replace the tube with a spare. Then, once home, you can patch the tube so you can use it again. Check out the videos and instructions below on how to do both.
In the videos below, BikeRadar's James Tennant explains how to carry out the task in a step-by-step walkthough, demonstrating the procedure on both a mountain bike and a road bike. Below the videos are step-by-step instructions in words and photos. You can buy patch kits, pumps and spare tubes at any good bike shop in your neighborhood or online.
Video: How to fix a mountain bike puncture
Video: How to fix a road bike puncture
Here are written instructions for those who prefer them to visual demos.
1 Find the puncture
Starting at the valve, check all the way around the tire’s tread to ﬁnd the cause of the puncture. Remove any glass or grit that you spot. Even if you ﬁnd one possible cause, continue checking the tire until you get back to the valve.
2 Remove the tube
Let the air out of the inner tube and push the valve up into the tire – unscrewing and retaining the valve ring, if ﬁtted. On the side of the wheel opposite the valve, slip a tire lever under the tire’s bead and a further tire lever about 5cm away. Pull the nearer tire lever (available from all good bike shops) towards you, lifting the tire’s bead over the edge of the rim.
Continue until one bead of the tire is completely free of the rim. Pull the tube out. If you want to take a good look at the tire, remove it from the rim completely. This can usually be done by hand without a tire lever.
3 Inflate the punctured tube, if patching — or jump to step 6 if replacing with a spare tube
Inﬂate the tube and listen for air escaping. Passing the surface of the tube close to the face is a good trick, as you can feel the air. If the hole still can't be found, re-inﬂate the tube and pass it through a bowl of water until you spot escaping bubbles. Then dry the tube before proceeding to the next step.
Take care – do not twist a push-fit pump on the valve. The pump should be pushed on straight and pulled off with a single straight pull. You can tear the tube if the pump is twisted sideways.
4 Prepare the tube
Select the correct size of patch – use a bigger rather than a smaller patch if in doubt. Roughen the surface of the tube around the hole with emery paper. There are two types of patches: those that need glue and those that don't. If yours require cement, apply a drop and spread it thinly with your ﬁnger over a 2cm circle around the hole. Allow to dry. Apply a second thin layer similarly. Once again, allow to dry – the rubber cement will change from shiny to matte. If using glueless patches, just make sure the scuffed area is clean and dry, and stick on the patch.
5 Patch the tube
Inﬂate the tube slightly – this will help to highlight the position of the hole. Firmly press the patch into place after removing the backing foil. If there’s a thin cellophane backing on the patch, it can be left on. If you have it, dust the repair with chalk or talcum powder to prevent it sticking to the tire casing.
6 Check the casing
Before putting the tube in, double-check the tire casing from inside for the cause of your puncture. If reinserting a patched tube, placing it over the tire will help to you to discover the position of the puncture. Run your ﬁngertips carefully around the inside of the tire to feel for the cause of the puncture and remove it.
7 Refit the tire
After repairing the tube and checking the tire for glass, thorns or any other sharp debris, reﬁt one bead to the rim. Slightly inﬂate the tube and reﬁt it to the rim, putting the valve through its hole ﬁrst. Starting at the opposite side of the rim to the valve, use your thumbs to lift the tire’s bead (the part of the tire that connects the rim to the wheel) over the rim. Work around the rim until there’s just one small section of tire left. Push the valve up into the tire and then, using your thumbs, ease the remaining section of the tire’s bead over the edge of the rim.
8 Make final checks
Check that the tube isn't trapped between the rim and the tire bead. Inﬂate to the point where the tire feels soft but has maintained its shape. Check that the moulding mark around the tire follows the rim evenly all the way around. If not, deﬂate a little and ease any high spots down and pull low spots up until the bead is ﬁtted evenly.
Inﬂate to the recommended pressure and check once again that the tire’s bead is still seated evenly and that the tire isn't lifting off the rim at any point. Finally, check that the tread is running reasonably straight by spinning the wheel. If not, deﬂate the tire and start again from the beginning of this step.
Puncture fixing tips
- When taking the tube out of the tire, note which way the tube was around in the wheel. This will help identify the position of the hole in the tube once the position of the object in the tire causing the puncture has been found.
- With a ballpoint pen, mark the hole with a cross so you can pinpoint it accurately.
- If you don't have any emery paper, roughen the tube by rubbing it against a stone or the road surface.
- For tires that blow off easily: ﬁt a thicker rim tape or a second rim tape – this prevents the tire bead sinking into the rim well and blowing off the opposite side.
- For tight tires: ﬁt a thinner rim tape if possible – this will make your tires easier to ﬁt and remove.
Two small holes in a tube placed fairly close together indicate a pinch puncture. This is caused by the tube getting trapped between the tire and the rim when riding over a sharp object. Tires not inﬂated hard enough are a frequent cause of this. Check that the tire’s sidewall isn't cut. If it is, you may need to use an emergency repair – see the ‘Emergency tire repairs’ section below.
A hole on the inner side of the tube indicates that the puncture was caused by a spoke head. Check around the inside of the rim to ensure that the rim tape properly covers the spoke holes and no spoke end protrudes above the inner surface of the rim. If this happens it'll need ﬁling down.
A less common cause of a puncture is a rough edge to the valve hole rim. The puncture will be at the base of the valve and will not be repairable.
The tell-tale snakebike sign of a pinch flat caused by inadequate air pressure
Check your tires for cuts in the tread, swelling in the sidewall, or serious wear. Tires with cuts, swelling or casing visible through the tread must be replaced. Remove any grit or glass embedded in the tread. Check your tire pressures with a proper gauge. Tires inﬂated to the correct pressure will have fewer punctures and a longer life. The recommended pressures are normally marked on the sidewall of the tire.
Emergency tire repairs
If you have a large gash in the sidewall, you'll need to cover it from the inside so that the tube doesn't bubble out. In a pinch, you can use an energy bar wrapper or a dollar bill folded over a few times. Put this folded piece on the inside of the tire centered on the cut. Then carefully remount the tire, pushing the patched section onto the rim last. Check that the patch is trapped at both sides. Inflate the tire and make sure that the patch is holding. This fix is only intended to get you home or to a bike shop. Replace this tire immediately!