These instructions are for repairing a rear flat tire. The process is the same for a front tire, just slightly easier since you don’t have to deal with the chain and gearing while removing the wheel.
1. Keep the bike right side up, and shift the into the most difficult gear in the back (smallest cog).
2. If you have caliper (rim) brakes, use the lever on the side to loosen the brakes. If you have v-brakes, push both sides in to remove pressure from the brake cable, and disconnect it. If you have discs, skip this step.
3. Stand on the non-chain side of the bike and open the quick release. Hold the wheel down with one hand and lift up on the bike with the other. The wheel should easily come out as you tilt it away from the frame. Set the bike down on the non-chain side.
4. If your bike has thru axles, you will need to unthread the axle until you can easily pull the entire axle out of the frame. Then the wheel can be easily removed.
5. Once the wheel is off the bike, start near a spoke and use the scooped end of your tire lever to grab the edge of the tire and work it over the edge of the rim. Attach the hooked end of the tire lever to the nearest spoke.
6. A few inches away from the first tire lever, use the scooped side of your second tire lever to work more of the tire over the edge. Once you have a few inches over the rim, work your way around the rest of the wheel to completely remove one side of the tire from the rim.
7. Pull the old tube out of the tire, beginning at the valve stem (the part where you connect a pump).
8. If you’re fixing a flat, check for the source of the flat before replacing the tube. Gently run your fingers through the inside of the tire, feeling for anything sharp, and visually inspect the outside of the tire for anything still stuck in the rubber. Remove anything that could immediately cause another flat. NOTE: Sometimes glass or other small sharp
objects can cause a flat tire. Run your fingers along the inside of the tire very carefully.
9. Take your replacement tube, and inflate it with enough air to give it just a bit of shape. This will make it easier to place in the wheel.
10. Start back at the valve stem hole, insert the valve stem, and work your way around the tire, tucking the tube under the entire way around.
11. Begin at the valve stem again, and use both thumbs to push the edge of the tire back onto the rim. It will become more difficult as you get more of the tire back inside the rim, but use your thumbs to tuck all of it under if possible. If the tire is too tight, carefully use the scooped end of the tire lever to press the rest of the tire back inside the rim.
12. Check that the tube has not been pinched by the tire by gently pushing the tire to the side as you work your way around the rim and look for any obvious pinches.
13. Using your pump, re-inflate the tire to the proper PSI. The flat is now fixed, and it’s time to get the wheel back onto the bike.
14. Make sure the quick release lever is on the opposite side of the chain, and use the end of the quick release to move the bottom part of the chain out of the way. Lay the top of the chain around your smallest cog (hardest rear gear), and gently push the bike into place.
15. Close your quick release lever, and close your brake if you have caliper or v-brakes.
16. If you have thru axles, insert the axle through the frame and hub, and then thread it in and close the lever.
17. Lift the rear wheel and give the bike a quick pedal to ensure everything is running smoothly.
18. Enjoy the rest of your ride.