How to fix a flat bike tire

A flat tire is annoying, but fixing it yourself is quicker than walking to a bike shop. With a few simple tools, it takes about twenty minutes.

What you need

• a puncture repair kit with patches, glue and sandpaper,
• two or three tire levers,
• the bike pump with gauge,
• a bucket of water,
• the multitool, 15 functions, or a wrench for the wheel nuts,
• a piece of chalk or a pen.

Step 1: check the valve

Sometimes the tire isn’t punctured, but the valve leaks. Pump the tire up a little, and put a drop of water on the valve. If it bubbles, tighten or replace the valve. Problem solved.

Step 2: take off the tire

On most front wheels and many rear wheels, you can leave the wheel on the bike. Let all the air out of the inner tube. Push a tire lever under the edge of the tire, opposite the valve, and lever it over the rim. Hook the lever onto a spoke. Do the same with a second lever ten centimeters further. Then slide one lever around the rim until one side of the tire is off.

Pull the inner tube out, starting opposite the valve. Push the valve out of the rim last.

Step 3: find the hole

Pump a little air into the tube. Move it slowly through the bucket of water, a short piece at a time. Where bubbles come out, you have found the hole. Mark it with chalk or a pen, and dry the tube.

Step 4: find the cause

Before you patch, find what caused it. Run your fingers carefully along the inside of the tire. A small piece of glass or a thorn often sits there still, and it will puncture the new patch at once. Remove it with the pliers of the multitool.

Step 5: patch

1. Roughen the area around the hole with sandpaper.
2. Spread a thin layer of glue, a little larger than the patch.
3. Wait until the glue is dry to the touch, about five minutes. This is the step most people rush.
4. Press the patch firmly onto the glue, and hold it for a minute.

Step 6: put it back

Push the valve through the rim first. Tuck the tube into the tire all around, pumping a little air into it so it holds its shape. Push the tire back over the rim with your thumbs, starting at the valve. Use the levers only for the last bit, carefully, so you don’t pinch the tube.

Step 7: pump to the right pressure

The right pressure is printed on the side of the tire. Use the bike pump with gauge, which fits both common valve types. City bikes often need 3 to 5 bar. Check that the tire sits evenly on the rim all around.

Prevent the next one

Most flats come from tires with too little air. Check the pressure every two weeks. Ride around glass, and replace tires when the tread is worn.

Ride safely after dark with the bike lights set, rechargeable.