How to Convert a Fixed Gear Bike to Variable Speed

Converting a fixed gear bike to variable speed gives you the ability to change to an easier or harder gear.

Before you convert your fixed gear bike into a variable speed bike, you need to check two important features. First, the frame must be wide enough to accommodate a wider hub and the additional gears. Federal law mandates that all bikes on the road have brakes, but not all bicycle frames are designed for brakes. Ensure that your frame has the correct holes in the fork and frame to attach brakes.

Things You'll Need

• Bottom bracket
• Bottom bracket tool
• Adjustable wrench
• 15 mm socket wrench
• 14 mm socket wrench
• Crank puller
• Cranks with double or triple chainrings
• Metric allen wrench set
• Pliers
• Chain
• Chain cutter
• Front and rear derailleur
• Derailleur hanger
• Rear wheel with cassette or freewheel hub
• Cassette or freewheel
• Cassette tool
• Brake/shift levers
• Brakes
• Brake cables and housing
• Shift cables and housing
• Cable cutters
• Cable ends
• Bar tape
• Grease

Instructions

Disassembly

1. Use the 15 mm wrench to loosen the nuts on both sides of the rear wheel on your fixed gear bike. Slide the wheel forward in the dropouts and lift the chain off the cogs. Remove the wheel and set it aside to reuse the rim tape, tube, and tire.

2. Use the chain tool to push one pin out of a link in the chain. Remove the chain and discard.

3. Use the 14 mm socket wrench to remove the crank bolt on both sides of the bike. Thread the crank puller into the crank arm as far as it will go. Turn the handle of the crank puller to the right, tightening the tool against the bottom bracket spindle to release the cranks. For self-pulling cranks, use a 15 mm allen wrench to remove the crank arms.

4. Insert the bottom bracket tool into the bottom bracket. Tighten the adjustable wrench around the bottom bracket tool and hold the assembly tight against the bottom bracket. Turn the bottom bracket toward the front of the bike to remove. On the drivetrain side of the bike, bottom brackets have reverse threads and do not loosen to the left.

Preparation

1. Use a rag to clean the threads inside the bottom bracket. Apply clean grease to the threads.

2. Remove the bar tape from the handlebars.

3. 

   Cassette cogs are not connected as a single unit like a freewheel

   Apply grease to the threads of the freewheel if using one, and hand-tighten the cogs onto the hub. If using a cassette, place the cogs on the freehub body, starting with the largest cog. Insert the cassette tool into the threaded cap and use the adjustable wrench attached to the cassette tool to gently tighten the cogs in place.

Assembly

1. Insert the wheel into the dropouts and tighten the quick release skewer and close the cam. Orient the wheel so the cogs are on the right side of the bike.

2. Install the bottom bracket cup in the left side of the frame and tighten using the bottom bracket tool and adjustable wrench. Turn the tool to the right to tighten. Install the right-hand side of the bottom bracket and, using the bottom bracket tool and adjustable wrench, tighten to the left.

3. Place the cranks on the bottom bracket spindle so the crank arms are oriented 180 degrees away from each other. Install the crank arm with the chainrings on the right-hand side of the bike.

4. Install the front derailleur just above the largest chainring so the outside of the derailleur cage does not touch the chainrings when you put tension on the spring. Tighten the clamp around the seat tube with a 5 mm allen wrench to hold the derailleur parallel to the chainrings.

5. Install the rear derailleur by using a 5 mm allen wrench to thread the derailleur into the derailleur hanger. If your frame is aluminum or carbon you may need to install a derailleur hanger. Derailleur hangers are molded to fit snug against the frame around the dropouts. Tighten the hanger into place with a 4 mm allen wrench.

6. Thread the new chain over the smallest chainring, through the front derailleur cage and over the smallest rear cog. Thread the chain around the front of the upper pulley of the rear derailleur and around the back of the lower pulley. Bring the two ends of the chain together and measure the correct length by putting a small amount of tension on the rear derailleur, just enough so that the bottom pulley no longer rests against the body of the derailleur.

7. Use the chain tool to cut the chain to the measured length. Ensure you cut the chain so one end link is male and the other end link is female. Holding the two ends together, insert the spare pin and push it into place with the chain tool. Use a pair of pliers to break off the guide pin. If the chain doesn't move freely, adjust the position of the pin with the chain tool.

8. Slide the brake and shift levers onto the handlebars and position them so the top of the hoods are level with the top of the bars. From the front of the brake, insert a 5 mm allen wrench under the brake hood and tighten the bolt on the outside of the unit.

9. Bolt the brake calipers to the frame at the front and back of the bike using the 5 mm allen wrench. Center the calipers over the wheels so the shoes are equal distances from the rims.

10. Trim the brake and shift cable housing using the cable cutters. Remove the housing from around the cables before you cut it. Ensure that the handle bars can turn all the way to the top tube without pulling the housing out of the stops on the top tube or the brake calipers.

11. Route the cables and housing to the brakes and derailleurs. Cables from the left-hand brake/shift lever go to the front brake and front derailleur. Route the right-hand cables to the rear brake and rear derailleur.

12. Loosen the brake cable clamps on the calipers and insert the cable behind the bolt. With one hand, squeeze the calipers together until the brake shoes almost touch the rims. Use the 5 mm allen wrench to tighten the cable clamp. Adjust the brake shoes so they sit parallel to the rim and when you squeeze the brake lever, that they lay fully flat against the rim and do not touch the tire. Use the cable cutters to trim off the excess brake cable.

13. Loosen the front derailleur clamp with the 5 mm allen wrench and pull the cable behind the bolt. With the clamp bolt still loose, pull the front derailleur out away from the frame to center the cage over the chain. Tighten the bolt and trim the excess cable with the cable cutters.

14. Hook up the rears derailleur by using the 5 mm allen wrench to loosen the clamp bolt. Pull the cable behind the the bolt and push the derailleur toward the wheel until the section of chain that goes around the bottom derailleur pulley is parallel to the section of chain that runs over the smallest rear cog. Tighten the bolt clamp to secure the cable and trim off the excess.

15. Cinch cable ends on all of the cut cable ends.

16. Wrap the handle bars with bar tape.

Tips & Warnings

• Some of the tools required for this work are expensive for one-time use. Instead of buying the specific tools, take your frame and parts to your local bike shop. For a small service fee they are usually happy to swap out bottom brackets or cut and install a chain to fit your bike.

• Before you remove your bottom bracket, use a pair of calipers to determine the length of the spindle. Some bottom brackets on a fixed gear bike may have a long enough spindle to accept a crank with multiple chainrings.

• If your frame is titanium, do not grease the bottom bracket threads. Apply anti-seize to the threads to allow you to remove the bottom bracket later.

• It's easy to tell the difference between the brake cables and the shift cables when deciding which goes where; shift cables are thinner than brake cables.

• Bicycle components are very brand specific and not all parts are compatible across brands. Make sure you verify the compatibility before purchasing parts.

• Bottom bracket tools are also very brand specific. Do not use a bottom bracket tool designed for one brand of bottom bracket on another brand because this will ruin your part and can ruin your tool.

• Cables have sharp edges that can cut you. When trimming brake and shift cables, use caution and wear safety glasses to prevent small pieces of cable from flying into your eyes.

References

• San Diego Union Tribune--Fixed Gear Bikes vs. Geared Bikes and the Risks
• How to Replace a Cartridge Bottom Bracket
• Calculating Chain Length