Punctures happen occasionally, even with tough tyres, so being able to 'fix a flatty' on the go is a great skill to have. It's not as hard as you think to change a flat tyre on the go.
If you notice a puncture while riding, slow the bike down gently and pull off to the side of the road. You're going to need a little space, so find a spot that's well away from the road and out of the way of pedestrians.
You're going to need:
- tyre levers
- a replacement tube
- a pump, and
- a 15 millimetre spanner (if you have nutted axles)
- it pays to carry a repair kit on your commute or any decent ride
Firstly, put the bike upside down so it's balanced on the seat and handlebars.
Now, if the front tyre of your road bike or mountain bike has a puncture it's a bit easier to change the tube as you don't have to deal with the chain. Unfortunately, in most cases, it's more likely to be the rear tyre. If the puncture is on the rear and your bike has gears, shift to the highest/hardest gear. You can do this by peddling the bike with your hand and shifting through the gears until the chain is at the outermost position on the rear wheel. This will make it easier to remove the rear wheel.
If you have a quick release skewer, undo it by flipping the lever and unscrewing the nut on the other side. If you have nuts on your axle, you'll need to undo them with a spanner, using the 15 millimetre spanner. The nuts don't need to come all the way off - just loosen them.
Remove the wheel from the bike. The tyre has a band that sits inside the rim called the bead. Take the valve cap and any lock nuts off the valve stem. Get the rest of the air out of the tyre.
With the skinny Presta valves, you need to unwind this valve core and then press it in. With the fatter Schrader values (like car valves) you need to press the little button hidden within the valve.
When all the air is out, you're ready to remove the tyre, starting opposite the valve as the bead is loosest here. Pop two tyres levers between the bead and the rim, about a hand's width apart. Lever them both towards the hub to pull the bead over the rim. Now you should have a section of bead over the rim on one side.
Using the tyre levers, work your way around the bead on the same side to remove it all the way. Now remove the tube. The bead should come then off the other side of the rim quite easily.
You have to see if you can find what caused the puncture. If it's a bit of glass or something still stuck in the tyre, you have to get it out. Start at some recognisable point, like the label. Examine the tyre carefully inside and out, running your fingers along the inside of the tyre to feel for any glass poking through.
It's worth checking the rim for any sharp or damaged bits as well. If you're all clear, you can put the tyre back on.
First put the bead on one side only. You shouldn't need tyre levers. Then put just enough air in the tube that it holds its shape a bit when it's draped over your finger.
Push the tyre aside, push the valve through the rim, then make sure that the back of the valve sits inside the tyre nicely. Put the tube back in place all around the tyre, taking care to avoid creases and twists. Then, starting with the valve, put the second bead back on. Again, you shouldn't need tyre levers until the last little bit. Then, you'll use the tyre levers again to push the bead back into place.
Now, go around the tyre, pushing the tyre back with your thumbs to make sure that there is no tube caught between the bead and the rim. Do this for both sides.
You're ready to start pumping up the tyre. If your pump has a gauge, that's excellent. The recommended pressure will be printed on the side of the tyre somewhere. Pump the tyre up to that pressure before reinstalling the wheel. If you don't have a gauge, don't worry. The tyre needs to be fairly firm; most people under-inflate tyres rather than over-inflating them. Squeeze the sides of the tyre - there should be a little give but not too much.
When reinstalling your wheel, make sure that it's straight in the bike. Tighten up the quick release skewer by doing up the nut on one side and then closing the lever on the other. It should take enough pressure that it leaves it a little dent in your hand but it doesn't hurt! About same pressure is required when doing up axle nuts.
Once your wheel is back in, you're done! Remember to buy a new replacement tube. If your tyre is getting repeated punctures, it may be worn out and need replacing.