It could happen to you and you may not always be riding with a friend who knows how to fix a flat for you. Practice fixing a flat at home to get the learning curve over with. If you need someone to give you an in-person demo, visit your local bike shop.
Step 1: Open the brake.
If you have a road bike, look for a lever to open the brake. If you have a mountain bike, unhook the cables of the brake.
Step 2: Remove the wheel.
To remove the wheel, either open the quick-release or unscrew the axle nuts, depending on your bicycle.
Step 3: Remove the tire and flat tube.
Unscrew the valve and let all the air out of your tire. Wiggle a tire lever under the edge of the tire and pry it off a little. Place another lever about half a foot away from the first lever and pry some more. Place the third lever half a foot away from the second lever, and pry again. Now you should be able to take the tire off with your hands. Remove the tube from the tire.
Step 4: Remove glass or debris from the tire.
First use your eyes to see if you can spot any broken glass or sharp pebbles. Then, run a cloth on the inside of the tire to see if anything snags. If you don’t catch and remove whatever caused the flat, you’ll be repeating this whole process very soon.
Step 5: Patch the tube (or, if you just want to use a new tube, skip to Step 6).
1. Make sure the tube is dry and free of dirt or debris.
2. Rough up the area around the puncture with a tool included in the patch kit. Glue will adhere better to a textured surface.
3. Apply the glue, but let the glue dry a little before placing the patch on. The glue itself is not actually the adhesive. It simply softens the rubber of the tube enough so that it will bond with the rubber patch.
4. When you put the patch on the tire, hold it as hard as you can for an entire minute. The more pressure you apply, the better the patch will hold.
5. Check to see that the patch has been sealed all around. If it hasn’t, glue can be used to fill the gap.
Step 6: Put the tire and tube back onto your bike.
1. Inflate the new tube slightly, so that there are no wrinkles.
2. Put the tube inside the tire.
3. With the tube and tire combo in your hand, stick the valve of the tube through its hole in the rim.
4. Work your way around the wheel, placing the tire-tube combo onto the rim, starting with the area closest to the valve. Never use a tire lever for installing a new tire–only use your hands. Otherwise you could pinch and puncture the tube and get another flat.
5. After the tube and tire are back on the rim, methodically circle the wheel, looking into the gap between the rim and the tire and make sure the tube is not stuck between the rim and the edge of the tire. Otherwise you will have an exploding and unsalvageable tube, not to mention a scary shock as you hear an incredibly loud and sudden blow-out from your bicycle while riding.
Step 7: Reattach the wheel to the bicycle.
You can either reattach the wheel now, or after inflating the tire. If you have fat tires however, reattach it now so you know it won’t be too inflated to fit between the brakes. Remember to reattach the brake.
Step 8: Inflate the tire
After you inflate the tire some, once again make sure that the tube is fitted correctly between the tire and the rim, with nothing sticking out. If the tube is sticking out, deflate the tire, reposition the tube and inflate again.
Step 9: Ride away!