A fixed-gear bicycle does not have a freewheel mechanism, which allows the fixed gear to move both forward and backwards. A fixed-gear bicycle also cannot coast, as the bike pedals will move whenever the bike is in motion. Fixed-gear bicycles also have only one gear, so there is no shifting. Fixed-gear bicycles are popular in urban areas--particularly with bike messengers--and require less maintenance because fewer mechanical parts are used on the bike. The most inexpensive method of building a fixed-gear bike is converting a freewheeled model. Almost any bike can be converted to fixed-gear, although road bikes with a horizontal dropout are best suited to the process.

1. Remove the rear wheel. Release the brake by unhooking the brake cable or releasing air from your tire. Shift your gears until the chain is on the smallest sprocket. Move the carbon wheels quick release lever on your wheel into the open position. Hold the bicycle wheel by the cap on the opposite side of the quick release lever and spin the lever counter-clockwise until the wheel becomes loose. Remove the wheel from the bike fork.

2. Remove the rear wheel. Release the brake by unhooking the brake cable or releasing air from your tire. Shift your gears until the chain is on the smallest sprocket. Move the quick release lever on your wheel into the open position. Hold the wheel by the cap on the opposite side of the quick release lever and spin the lever counter-clockwise until the wheel becomes loose. Remove the wheel from the fork.

3. Remove the rear brake and shifter. Follow the loose cable to the corresponding brake lever. Loosen that brake lever with the 5mm allen key and separate the brake lever from the shifter. Turn the shifter to the highest gear. Loosen the allen bolt on the shifter and slide the shifter off the bike. Slide the rear brake off with it. Fixed gear bikes do not need rear brakes (they do need front brakes), and there are no gears to shift.

4. Remove the derailleur. Insert a hex wrench into the derailleur mounting bolt, and with a counter-clockwise motion twist until the derailleur comes off. You will not need it anymore.

5. Remove the bicycle crankset. Insert a 14mm crank bolt wrench over the nut of the crank. Hold the wrench firmly and rotate the crank arms in a forward direction. Remove the nut. Insert and thread a crank arm extractor into the crank arm. Hold the crank arm extractor steady and rotate the crank arms backward until there is tension on the extractor. Rotate the extractor forward once there is sufficient tension and the crank will come off.

6. Replace the crankset. Typical fixed gears have a 165mm-length crank with a 3/32 ring. Slide the crankset onto the bike. Grease the bolts before inserting them into the crankset and tighten with a torque wrench.
 
7. Install a rear wheel with a track hub. Apply grease to the cog threads and thread the cog over the hub in a clockwise motion. Tighten the cog with a chain whip. Place the lockring over the cog and use a lockring tool to tighten the lockring without stripping the threads. The lockring will prevent the rear sprocket from unscrewing when applying resistance to the pedals. Insert the rear wheel and tighten the bolts securely with a 15mm wrench.

8. Install the chain. Fixed gear bikes cannot have slack on the chain. The chain needs to be tight. Release as many links as necessary with a chain tool until the chain is straight when wrapped around the front and rear sprocket.