Getting a puncture while you’re riding is an inconvenience, however it’ll happen to all of us that ride regularly at some point. You can reduce your chances of getting one by making sure you change tyres when they start to wear out, but even then it only takes a sharp piece of glass or a thorn, and you’ll have a flat tyre. We always recommend, at a minimum, you take out a multi tool, along with a pump, a couple of spare inner tubes, and a couple of tyre levers. And it’s those last three we’ll need today to fix that flat tyre.
The easiest way to get the back wheel out is to firstly put your chain down to one of the smallest sprockets here, on the back. So just click the lever down, [and] give it a few turns until it’s on that smallest sprocket. Put the wheel on the floor – don’t be tempted to put your bike upside down and rest it on the levers, because you can potentially scratch them. Just gently put it down on the non-drive side, preferably on a bit of grass.
It’s time to remove one side of the tyre, but you don’t need to take it off completely. Firstly make sure that any air is completely out, [then] take one of your tyre levers, stick it in underneath the beading on one side of the tyre, put your other one a few inches further around (basically where you can get some grip underneath the bead). Sometimes [with a tyre] you can just start to slip your tyre lever round like this and it will fairly easily come off all the way around.
So, one side of the tyre bead is completely off. Pull it all the way out until you get here to the valve, lift the tyre over to reveal the inner tube, and then you’ll just be able to pull that inner tube out. Put it to one side on your bike and you’ll know that it’s the punctured one.
Right, before we go and put the brand new inner tube in, we want to check what’s caused this puncture in the first place. If it’s been a pinch puncture and you just hit a pothole very hard, that’ll be very obvious. However if it’s gone down slowly and you didn’t really notice until it began to go soft, you’ll want to go around the inside of the tyre carefully with your hands. I say carefully because of course whatever’s penetrated through your tyre and inner tube is likely to be very sharp and it could penetrate through your skin as well.
So in this case, the offending article is a sharp thorn, which I’ve been able to get out using my thumbnail. So once you’re satisfied you’ve got the offending item out of the tyre, it’s time to put the new inner tube in, and that is much more easily done if the tube has got some shape to it and is not just flat like this.
You’ve got a couple of options: you can simply undo the valve again here and blow it up yourself, or if you don’t want to do that you can simply attach your pump and do the same thing with that. It doesn’t need to be too pumped up, just to give it a bit of roundness so it sticks inside the tyre a bit easier. Then once you’ve got the shaped tube, do the valve back up here, find the valve hole on the wheel, which in this case is here, and then simply drop the valve through it after you’ve bent the tyre backwards. Then you want to get the bead over the inner tube there at the valve to start with, and you can start to tuck the inner tube in all the way around.
So once the tube’s bedded in, it’s time to start putting the bead back over onto the rim. In some instances, I think like possibly on this one, you can do the whole thing by hand. However if it’s not that easy and it’s a bit too tight, you can simply put the tyre levers up and use them to bend the bead of the tyre back on. Nut just be careful again that you don’t pinch the inner tube with your tyre lever.
Once you’ve got it seated back on the rim like this, we want to go around it step by step pulling it over on the side you put it back on, just to make sure you can’t see the inner tube protruding underneath the rim of the tyre. Because if you do and you start pumping it back up to a high pressure, it can actually explode again. So I’ve just got a bit here where you can see the inner tube underneath the tyre so before we start to pump it up we want to make sure that that inner tube is firmly inside the tyre. There’s no specific technique for this, it’s just simply a case of, you know, trying to roll it around until you can’t see the inner tube any more. On both sides. Once you’re happy with that, you can begin pumping.
Right that’s pretty hard now, reckon that must be somewhere up toward 100psi. And just one last check it’s seated properly: you give the wheel a quick spin, to make sure that it’s fairly smooth all the way round and if you get any big bobbles up and down in the tyre, it generally means that you’ve got your tube snagged underneath. Ok we’re ready to put that in. Just do the valve up here again and we’re ready to put the wheel back into the bike.
So almost in the same way that you put it in, push the rear mech down onto the cage part at the back to make sure that’s the case and as we’ve already put it into the smallest cog, that’s where you want to rest the top jockey wheel which should just slip in. OK before you set off, just give it a bit of pedalling, make sure that the chain’s still seated properly on both the chainring and the cogs at the back, you might even want to put it up a few cogs if you’re starting back on a climb like I am, before we get going.
Then it’s just a case of clearing your rubbish and your tools up.
One last thing though, before you get on your way: if you have loosened your cantilever brake up to get your wheel out, make sure that you do it back up!