How to build a Single Speed

Scrounge up a bike. No, don't steal it. Bad karma will come your way in the form of rabid bikers hunting you down and beating you with old seat posts. We're going to assume you are starting with an already assembled geared bike. Sorry, but this isn't "Bike Assembly for Dummies". A frame with horizontal dropouts is best, but not mandatory.

Remove the shifters, derailleurs and their cables. Build a small fire. Burn these parts. (You might want to wait on the rear derailleur).

Figure out what gear ratio you want to run. MTB - Try starting with 2:1 (i.e. 32 up front, 16 in the rear). Road - try something like a 2.8:1 (42/15) or 2.47:1 (42/17). If you've got parts laying around, use them first to experiment. They're free and you might be changing things depending on your terrain.

Remove the extra chainrings from the crank. You only need one, so pick the one that fits with your decision in #3. Get some BMX style chainring bolts or use some spacers with the ones you've got so everything fits together nice. Try the ring in the middle position. You want a straight chain line when you are done messing with the back wheel.

Remove the rear wheel. Cassette - go to 5.a. Freewheel - go to 5.b.

Remove the cassette. Bust it apart to get the cogs and spacers. Save the lock ring. Pick the appropriate cog for the decision you made in #3. Find some more spacers. If you don't have any, take your local bike shop guy a pizza and ask him if he has any junk cassettes you can cannibalize. Or, get a piece of PVC pipe that fits exactly over the freehub body and cut to length as needed. Space the cog on the free hub so you have a straight chain line with the front ring. Put the lock ring on and reinstall the wheel.

Assuming this is a multi-geared freewheel, remove the freewheel. If not multi-geared, what are you doing reading this - you probably already have a SS. Go to the LBS and get a BMX freewheel in the size you decided on in #3. Thread this on and reinstall the wheel.

Shorten your chain. Horizontal drops - go to 6.a. Vertical drops - go to 6.b.

Double check the chain line, snug the wheel up so you have tension on the chain without binding and tighten the rear wheel. Adjust your brakes if necessary.

You've got a little more work pal. If you are lucky, you can remove some links and the chain will fit nice and snug. Hate to break it to you, but it probably won't, so here's what you do. Shorten the chain as much as you can. Now you need a chain tensioning device to pick up the slack and keep the chain on track.

Option 1: Surly and Paul's both make single speed chain tensioners for these conversions.

Option 2: You can use that rear derailleur you took off in #2 (didn't burn it yet did you?) and play with the adjustment screws to get things aligned.

Option 3: Do it yourself - head over to the Dragon Tongue SS page for some instructions on building your own.

Option 4: Get an eccentric axle from Fixed Innovations. This will allow you to adjust chain tension with a vertical dropout.

Get the tensioner installed, check the chain line and tighten the wheel.

Take it for a test ride. Readjust.

Have a beer. :DGo on another ride. Think about what little maintenance this bike will be.

Repeat #8 as necessary.