1. First step is to take a quick look around the tyre to see if you can spot the thorn. If it’s wet, look for bubblings. If you see the thorn, pull it out. At this point, most of the remaining air in the tube will escape. Let the rest out through the valve – Schrader (car-type) valves will need the inner core pushing in, Presta (thin) valves require the knurled brass bit to be undone and then the core pushing in.

2. The trick to getting tyres off without levers is to work all the slack in the bead around to one point. Rims are deeper in the middle than at the edges, so use this to your advantage. Stand the wheel up in from of you with the valve at the top and push the tyre beads together and down into the rim.

3. Then use your thumbs to “push” the tyre around the rim from top to bottom. You’re trying to get the bit of slack you’ve obtained from pushing the top of the tyre into the well of the rim all the way around to the bottom. As you work your way round you’ll find yourself picking the wheel up with the valve side resting on your upper legs somewhere.

4. When your thumbs meet at the bottom, you should have generated enough slack to push the tyre sideways over the rim. Push outwards and down with your thumbs – your legs will give you something to push against.

5. With one bit of the tyre over the side of the rim, you should be able to grab it with one hand and the wheel with the other and pull the two apart with a flourish and a small ripple of applause.

6. Put the wheel to one side and pull the tube out of the tyre. If it seems to be stuck, gently peel it away from the inside of the tyre. If it’s stuck in one place there may be a previously-unseen thorn there. If you can find it on the outside of the tyre, pull it out. With tube and tyre separate, hand the old tube to a willing assistant to roll up and run your fingers around the inside of the tyre to locate any further thorns. If you don’t find any, check again but don’t worry too much – they often just fall out. Or you may have sustained a “snakebite” or impact puncture. If you hit a rock fairly hard and the tyre went down very quickly, chances are that you bottomed the tyre out and pinched the inner tube between the ground and the edge of the rim.

7. Partially inflate the new tube. This makes it easier to handle and makes it less likely that you’ll trap it between the tyre bead and rim when reinstalling. Then get the tyre and pop one bead back into the rim. If your tyre’s directional, make sure you get it on the wheel the right way round – check the sidewall for arrows.

8. With the tyre half on the wheel, pop the valve of the new tube through the hole in the rim. If it’s a Presta valve there ought to be a lockring to hold it in place. Take that off before putting the valve in and replace it on the hub side of the rim. If the valve won’t fit through the hole, you’re probably trying to put a larger Shrader valve through a Presta-sized hole. Debates rage over with valve is better – we don’t really care, but have all our rims drilled for Shrader (so we can use either tube) and tend to carry Presta spares (so anyone can use ours). You can get grommets to fill up the gap that results from using small valves in large holes.

9. Adopting a similar position to when you removed the tyre, push the inner tube completely into the tyre all the way around. If it doesn’t seem to want to fit, let a little air out – you need just enough so that it holds its shape.

10.Starting at the valve, push the other tyre bead into the rim and then use more deft thumb action to pop the bead into place all the way around. Take care not to pinch the tube between bead and rim. If you pushed it fully inside the tyre it shouldn’t be a problem, but watch out for it anyway.

11.The last couple of inches may need a bit of grunt. Again, you’ll have one side of the tyre on your legs, giving you something to push against to get the last bit of bead over the edge of the rim with a satisfying “pop”. Check around the tyre on both sides to make sure it’s properly seated and reinflate. And don’t forget to mend the old tube when you get home…