A sharp object on the ground can penetrate the tire and puncture the inner tube, causing air to escape and leaving the rim vulnerable to damage. A rear tire is particularly susceptible to flats, due to the weight of the rider being placed directly over the tire. Fixing a flat yourself is a quick and cheap way to get your bicycle back on the road.
Things You'll Need: Adjustable wrench (as needed), Tire levers (set of three), Replacement inner tube
Tire and tube removal
- Shift the chain to the outermost gear combination. This will place the chain on the smallest rear sprocket and largest front chain ring.
- Use an adjustable wrench to loosen the rear wheel axle nuts. Newer models may feature an axle skewer with a quick-release. In this instance, no tools are required---simply open the release arm and loosen the nut on the other end.
- Elevate the rear wheel, and push it from behind to dislodge the axle from the frame. Remove the wheel from the bicycle.
- Insert the flat end of a tire lever beneath the bead of the tire and wrap the opposite, hooked end onto the nearest spoke. Be sure and work opposite the valve stem. The stem will be the last portion of inner tube removed from the wheel.
- Insert a second tire lever beside the first lever, mirroring Step 4.
- Insert the third, and final, lever on either side of the above pair, and slowly rotate the lever around the circumference of the tire bead. The first two levers will probably drop away from the tire. This is fine.
- Reach inside the tire, opposite the valve, and remove the inner tube from the tire. Again, the valve stem will be the last portion of the tube removed. Simply pull this from the hole in the rim.
Inner tube installation
- Remove the cap from the valve on the replacement inner tube. With your mouth, blow air into the valve. This will give the tube a little bit of shape, making installation easier.
- Insert the valve stem through the hole in the rim, and gradually work the tube onto the rim.
- Use your thumbs to fold the tire bead back onto the rim. Once the bead is in place, inspect the tire to make sure there is no inner tube showing anywhere.
- Inflate the tire at or slightly below the recommended PSI (pounds per square inch). The recommended PSI will be printed on the sidewall of the tire.
- Screw the valve stem cap onto the valve and insert the wheel back onto the bicycle. Check that the axle is firmly seated in the frame.
- Tighten each of the axle nuts. Alternatively (for bikes with quick-release skewers) tighten