Step 1: Removing the tube
The first part is getting the punctured tube out of the tyre. The easiest way to do this is with tyre levers although you can some times get tyres off just by using your hands.
Levering the first bit of the tyre off the rim is the hardest part. Let all of the air out of the inner tube and push the lever end of the tyre lever under the bead of the tyre. Then push down hard on the end of the lever and lift the tyre up. Some tyre levers will have hooks on the end so you can attach them to the spokes to hold them in place at this point, but remember that the more you stretch the tyre, the harder it’ll be to get the second level under the bead. With many tyres, this likely wont be a problem, but if it’s a particularly tight tyre, it might make it damn near impossible to get the tyre off.
The next step is performing the same action with the second lever while making sure the first one stays in place. Once you’ve lifted that second part of the bead, it should sit outside the rim, leaving you free to lift the rest off the tyre off the rim, or do the same thing for a third time, if it needs a bit more persuasion. At this point it’s actually possible to slide the tyre lever around inside the bead of the tyre, pulling it all out of the rim. As we’ve alluded to, it’s often possible to do this earlier in the procedure, but again it all depends on how tight and stiff the tyre is.
Once you have half of the tyre completely out of the rim, you can remove the tube. After the tube’s out, check it over to see where the hole is. There are various methods to do this. One if the hole is obvious enough, is to just look. Another, easier, way to do it is to pump air through the tube and listen/look/feel for air escaping. Yet another way (and this one only generally works for fixing punctures when back at home, for obvious reasons) is to submerge sections of the tube in a tub of water while pumping air through the tube. That way you can see the air bubbling out of the hole when you reach the damaged section.
Something that’s easy to forget in the haste of fixing a tube is to check the tyre. If your puncture’s been caused by something piercing the tyre, the last thing you want is to fix the tube, stick it back in the tyre only to puncture again five minutes down the road because the piece of glass or offending item is still stuck in the tyre. So check the tyre thoroughly – use where the hole is in the tube to clue you in to where the tyre may be punctured – and make sure any debris is cleared. In the case of bad punctures, where there’s a hole in the tyre, you may need a tyre boot to cover that hole until you get home.
Step 2: Repairing the tube
In your puncture repair kit, there should be a small piece of sandpaper. Use it to lightly rub around the damaged tube in the area of the hole to provide a better surface for the rubber solution to grip.
Next, apply the rubber solution to the tube. The reason we call it rubber solution rather than glue is because if you treat it like conventional glue, you’ll have no joy at all trying to fix the puncture. Basically, you need to apply enough to cover an area the size of the patch and you don’t need a massive amount of solution. Once applied – and this part is vital – leave it for around 30-60 seconds. You want the solution to go tacky, runny is no good at all, and you don’t want to apply the patch until the solution is just the right consistency.
While you’re waiting, get the patch ready by pulling the silver foil or similar off the back, but don’t touch the side you’ll be applying to the tube as you don’t want to get dirt on it.
Next, carefully apply the patch to the tube. Sure, it’s not exactly surgery, but you don’t want to mess it up and leave part not stuck down properly because that means it won’t seal the tube and you’ll have to start all over again. I usually hold the patch against the tube for a good 30-60 seconds to make sure the whole thing is securely stuck down.
Step 3: Refit the tube
Either pump some air into the tube to check that the patch has been installed correctly or, once you’re confident enough in your ability to do it first time, stick the tube back in the tyre, inflate and you’re good to go.
Fixing a puncture is really a very simple task. But, like everything, you’ll probably have to muddle through the first few times before you get the technique dialled and it becomes second nature. I’ve had tubes with multiple patches on that have lasted for hundreds more kilometres after the original puncture, so learning how to do this properly will genuinely save you money, especially as repair kits are usually a few pounds and can fix multiple tubes, whereas new tubes are anything between £3-10 each, or even more if you want something very fancy.