Liz Bernier is the Bike Coordinator at the UCLA Bike Shop in the John Wooden Center. She teaches all types of courses on bike maintenance, including how to build your own bike wheel. Go to UCLA Recreation's website for upcoming workshops.
Did you know that inflating your tires weekly to the proper pressure and replacing them when they’re worn can help prevent flats? It’s worth the effort. If you do eventually get a flat, here are some tips about how to fix it:
What to carry:
- Frame pump with a pressure gauge
- 3 tire levers
- Extra tube (stored in a plastic bag and coated with talcum or baby powder)
- Wrench (for bolt-on wheels)
- Patch kit
How to fix a flat:
- Flip the bike into an upside-down position or lay it on the side of the bike without the chain.
- Remove the wheel. This step may require opening the brake by unhooking or releasing it. For quick-release wheels, open the quick-release lever and, if necessary, unscrew the nut on the opposite side a few turns. For bolt-on wheels, use your wrench to loosen the axle nuts. For rear wheels, shift the rear derailleur to the smallest cog, release the wheel, then pull the derailleur towards the rear of the bike while pushing the wheel past it out of the dropouts.
- Remove the tire. If this step is difficult, place one, two, or three tire-levers under one bead of the tire (not under the tube) within two inches of each other. Push this bead over the tire levers and off the rim. Separate the rest of this bead from the rim with your fingers. Use the same technique to remove the other bead of the tire from the rim.
- Remove the tube from the tire. Inflate the tube to find the hole and try to understand what caused it (e.g., puncture, blowout or pinch).
- Check the tire for debris and holes. Remove anything stuck in it (e.g., glass, thorns, metal). If the tire has a hole larger than 1 or 2 millimeters, cover the hole from the inside of the tire with a patch.
- Either patch your damaged tube or use your spare. Inflate the tube enough to give it a round shape, then place it into the tire without folding or twisting it.
- Check the rim strip to make sure it covers the spoke nipples or spoke holes well. Make sure there isn't anything sharp on the inside of the rim.
- Install the tire. First, put the valve stem through the rim hole and push one bead of the tire onto the rim. Next, push the second bead onto the rim starting at the valve stem and moving away from it in both directions. For difficult-to-mount tires, release the air from the tube. Then, lean the wheel against your thighs and push the second bead over the rim with both hands. Be careful not to pinch the tube between the tire and rim.
- Inflate the tire about halfway, then spin the wheel to check that the tire is seating properly. If it is, inflate the tire to the range specified on the sidewall. Spin the wheel again to ensure that the tire is still seated well.
- Reinstall the wheel by putting it all the way into the dropouts. For rear wheels, place the axle between the top and bottom sections of the chain and set the chain on the smallest cog. Pull the derailleur backwards to allow the wheel to slide past it into the dropouts.
- Secure the wheel by closing the quick-release lever properly or tightening the axle nuts well.
- Re-engage the brake, take a test ride, and off you go!
Have any questions for Liz? Send them our way, and we'll try to answer it in a future blog post.