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Fixing flat
bike tyres
If ever you run into a puncture on a bike ride, it’s good to know how to get it fixed so you can get going again. If you have air leaking out of your tyre, it’s important to locate the source and problem behind the leak as quickly as possible.
Has the leak just started, or has it been happening over time? Are your tyres often flat, even when you’ve just inflated them? Or do you notice air suddenly escaping from your tyre?
Read on to learn how to identify the cause of the problem and fix it. It’s worth noting that we’ll be discussing traditional bike tyres in this guide rather than tubeless. Some of the steps will require knowledge of wheel removal, which we'd recommend getting comfortable with before attempting to repair a flat tyre.
How to fix a punctured tyre
Bike tyres are usually punctured by sharp objects on the ground, which can pierce the tread or the tube. Sharp thorns, metal, and broken glass are often the culprits for flats.
If your bike puncture is too big to repair, it’s best to change your tyre. If the puncture is smaller, you can attempt to fix the tube and save yourself from having to buy a replacement tube or tread.
Before attempting the repair, carefully check the tread and remove all sharp objects so that you can re-inflate the repaired tube smoothly.
To fix the tube, you’ll need a bucket of water, a bicycle pump, a bike repair kit, and a felt-tip pen. Follow the steps below.
Inflate the tube and immerse it in the water. Little bubbles will come up, showing you where the puncture is located.
Put your finger over the hole, take the tube out of the water, and mark the location of the puncture with the felt-tip pen.
Sand down the area around the hole with the sandpaper from the repair kit.
Apply the vulcanising solution/sealant around the damaged area. The solution should be runny; very viscous or thick solutions are usually too old and should not be used. Apply a thin, even layer of the solution over the damaged area.
In your repair kit, you’ll usually find a patch. Press this patch firmly onto the hole and hold it in position for 5 minutes to give it time to set.
After the 5 minutes are up, remove the foil from the patch. You can now slowly inflate your tyre and confirm if the patch has fixed the puncture.
Diagnosing bike valve issues
All bike tubes have a small metal tube that allows you to pump air into them. Inside this small tube is a valve that prevents air from escaping. Most traditional tyres use Schrader valves as opposed to Presta valves.
If you notice air escaping from your tyre over time (resulting in a flat tyre), it could be that the valve has come loose due to the pressure in the tube. If the small bolt ring that holds the valve in the rim is even slightly loose, air will escape from the tyre. Therefore, these bolt rings should always be tightly fastened.
How to tighten valve bolt rings
First, remove the valve cover from the valve. You should see a small female screw; loosen it carefully to expose the valve.
If the tyre has too much air, all you have to do is press the pin on the top of the valve, which lets excess air escape.
Finally, fasten the valve and put the valve cover back on.
Spot leaks in your tyre rubber
If you’ve repaired your tyre and checked the valve, but you’re still finding that it goes flat again after a few days, then it might be that there’s a sharp object in the rubber. If left unchecked, this will continue to damage your tyre tube until it’s removed.
Another possibility is that the outer tread has some serious holes or tears, so that the inner tube isn’t very well protected. This means the tube is exposed in places that can lead to small leaks, punctures, pierces, or even bursts.
Small, superficial tears in the outer tread are not necessarily a reason to buy a new tyre. However, we’d recommend keeping an eye on these, as it’s quite easy for a small tear to develop into something more substantial.
If and how quickly those tears develop can depend on things like your cycling style, the types of surfaces you cycle on, and even UV rays. Our general advice is to get a new tyre if you detect deep grooves in the rubber.
Issues with the rim or rim tape (liner)
Your bike rims are a braking surface; brake blocks from the rim brakes will press against the metal of your rims as you brake to help you slow down. A natural consequence of this is a lot of wear on your wheel rim, which then means it may need to be replaced. If your rims are worn, this can then impact your tubes.
Rim wear indicators
Most bike rims will come with a wear indicator. These are typically either a groove that runs around the entire rim, or a hole. If these indicators disappear, then it’s time to get a new rim.
Tips on rim liners & installing new tubes
Before you install a new tube, check that it comes with a rim liner. This will protect the tube from any damage from the rim itself. It’s important to monitor your rim liner over time; displaced or worn liners can allow mud or dirt to enter the tube, which can result in punctures.
Tubes that are not properly aligned on the rim are also vulnerable to damage. Make sure that the rim width matches the size of your bike tyre. The rim liner should be wider than the inner side of the rim itself by 2–4 mm.
Check your tyre pressure
Your bicycle tyres’ pressure should also be kept at an ideal level to minimise the chance of punctures in the tyres and the tubes.
Generally, tyre pressure requirements depend on the road surface, the kind of tyre, and the type of bicycle. Wider tyres need less pressure than narrower ones. To check your tyre pressure, you can use a specific pressure gauge. Some bike pumps also come with a pressure gauge that will tell you your current pressure as soon as you connect it to your valve.
FAQs
What causes a flat bike tyre?
Flat bike tyres can be caused by several issues, including punctures, worn rims, incorrect tyre or tube placement, and more.
Can I ride my bike with flat tyres?
We strongly recommend that you do not ride your bike with a flat tyre, as this can damage your wheels.
How do you fix a flat bike tyre?
How to fix a flat bike tyre will depend on the cause. Simple punctures can be repaired using a repair kit, but wider issues caused by rims may mean replacing your tyre tube.