How to Pump Air Into Bike Tires

Closeup of outer tire. Inside is an air filled inner tube.

The tire on a bicycle is a durable rubber tube filled with compressed air. This tube is protected by another piece of rubber used for direct contact with the road. Tires built this way are lighter and absorb road impacts better than solid rubber tires. Though generally superior to older types, air-filled bicycle tires are susceptible to puncture and air leaks through cracks and faulty valves. With low air pressure inside, the tire cannot support itself and you won't be able to use the bike.

Things You'll Need

• Bike air pump (either electric or manually operated)
• Pressure gauge

Instructions

1. Unscrew the protective thread cap from the valve stem on the bike tire.

2. Connect the air pump's end connector to the valve stem of the tire. The connector will either screw on or have a latch-type mechanism to make an air-tight fit.

3. Pull the bike pump's piston (handle) up and push back down. Repeat. When the piston moves up, air is pulled into the cylinder of the pump. When the piston is lowered, the air is forced into the bike tire.

4. Measure the pressure inside the tire. Do not over-inflate. If you do, the tire's inner tube may rupture.

5. Replace the cap on the tire's air stem. This will keep out dirt and reduce air leaks from a mildly faulty valve spring.

Tips & Warnings

• Check the maximum PSI (pressure per square inch) the inner tube can support. It's usually written on the surface of the tire.

• Some pumps use a double valve and two cylinder chambers to simultaneously pull in new air and force old compressed air all in one stroke of the pump's piston. In this case, fewer strokes are required to inflate a tire, although more effort for each stroke will be needed.

• If the tire will not inflate, remove the inner tube off the bicycle rim and submerge in water. Air bubbles will rise from the point of puncture.

References

• Bicycle South: How to Air a Tire