How to fix a flat tire on a bicycle
March 6, 2020 Filed under Advice
This advice is cobbled together from various internet sources.
Step 1: Remove the wheel and tube
Your best friend here is a pair of plastic tire levers.
Unscrew the little metal ring at the base of the valve and remove it, so you can separate the tube from the tire. Insert one lever between the tire and the rim, just next to where the valve is, and lift that part up and over the edge of the rim so it’s outside it. Usually a tire lever has a little anchor on the opposite side that you can then use to fix the lever in place by hooking that end onto the nearest spoke.
Leave that lever in place, and grab the second lever. Use it the same way you used the first, except instead of hooking it onto a spoke, drag it in a circle around the inside of the tire, levering the whole tire off one side of the rim.
With one side of the tire off, you can then grab the tire and pull the other side over the rim in the same direction, removing the tire entirely with the tube still inside it. Some people who are in a hurry will try to pull the tube out from between the tire and the rim without taking the tire all the way off, but I don’t recommend this. If you take the tire all the way off, you can check the inside for the piece of crud that caused the flat in the first place, and remove it.
Step 2: Find the puncture
Often times a puncture is very hard or even impossible to see. Especially a slow leak. Your best bet is to re-inflate the tube a little bit, then immerse it in water and watch for bubbles to rise. It probably won’t be a dramatic leak when you find it. In fact you may need to squeeze the tube a little bit to drive air through the puncture, in order to find it.
If you don’t have a spare and need to fix the leak “in the field”, and you don’t have any water to spare, you might want to try listening for an obvious “hiss” as you run the tube close to your air. Another way that works even in loud traffic (or if you’re deaf) is to move the tube past your open mouth and feel the air from the leak with your lips.
Once you’ve found the hole, mark it with something obvious. Hopefully you have a pen nearby, or you can try to place your fingernail near it.
Step 3: Roughen the area around the leak
To work with the tube, you need to get it pulled taut and flat with the puncture centered. You can take your tire levers and snap them together, then wrap the tube around them (it’s what I do) or you can wind the tube around a handlebar or a big stick (also good), or lay it across your knee (I don’t recommend this). The point is to get the area exposed and flat where it won’t slip around.
To roughen, you can use the little square of sandpaper that comes with a puncture kit, or a nail file on your pocket knife, or something similar. The important factor is that whatever you use, it can’t leave any residue like grease or dust.
The area you roughen should be bigger than the patch you’re applying it to, and if this is the first time you’ve done this, you’ll want to roughen it up a bit more than you think.
Step 4: Apply vulcanising solution
This is the tube of stuff that comes with most patch kits. Or, if you’re using a pre-vulcanized stick-on patch, this step is done for you: The solution is applied to the underside of the patch already.
Spread the solution over an area that’s larger than the patch, then leave it to cure for at least five minutes. Don’t proceed until this curing is done: This isn’t glue; it’s a surface preparation that makes the tube a much better bonding surface for the patch.
Step 5: Apply the patch
Patches usually have a foil backing. The backing is usually in two parts, so you can peel half of it off at first, then put the patch in position, then peel the other half.
Peel half the backing off, taking care not to touch the underside itself. Make sure the patch is centred over the hole, then press it down into place firmly for 30 seconds or so. Then peel out the other half of the backing, being careful to lift that half of the patch as little as possible. Then press down the entire patch for another minute or so.
Step 6: Inflate the tube (just a bit)
You’ll want to inflate the tube just a little to get it back inside the tire easily. As you do, check that the patch stretches with it. If a gap appears under one edge of the patch, remove it and start again. You’ll need to roughen the tube more thoroughly, and let the vulcanising solution dry for longer.
Once the patch looks solid, you can prevent the tube from sticking to the inside of the tire by getting a little road dust or talc around the patch.
Step 7: Check the tire for the vile beast that did the deed
Before you put the tube back inside the tire, grab the tire and run your fingers carefully around the inside. You will probably find a piece of wire, or glass, or a thorn, or something else that shouldn’t be there. Keep looking until you find something. If you don’t, there’s a good chance you’ll just spring another leak a few more miles down the road.
Sometimes if you can’t find the thing on the inside, you can see it on the outside of the tire, so have a look there next.
Step 8: Get the tire back on the wheel
Use the tire levers to put the tire back on, in a reverse of the procedure you used in step 1. Here’s some advice for getting a stubborn tire back over a rim. Once the tire is in place, re-inflate it in two or three stages, rather than taking it all the way up to like 100psi in one go. It gives the patch more time to stretch without breaking.
Don’t forget to re-apply the metal ring you removed at the beginning!
