Build a "Single Speed" from the Reject Pile (or real cheap anyway)
Wanna try a single speed? Don't got an extra $2000 for a full blown, deluxe, custom "bro built" unit?
A note about Refuse Piles:
Not all refuse piles are the same. I'll grant you that. I'll admit right now that I have an unfair advantage in that, my refuse pile is particularly well stocked. But, it is inappropriate to throw the stuff out, and I see a lot of stuff each year. What better use could it go to than a weird bike? (No - I am not shipping it to you - don't ask). With a little imagination, even less cash and some beer to trade I'm pretty sure the bros at the local bike shop will help you out with some of the stuff they have around too.
Frame and fork:
True single speed frames have horizontal slots in the dropouts so you can adjust the chain. The frames we converted in the shop used those. They work great, but you need a welding torch, or a framebuilder, and nutted axles on your hubs. Some frames have horizontal road dropouts too, and these will work in some cases. But they are rare and MTBs haven't had dropouts like this for a long, long time. That's why a lot of people pay a frame builder to weld a set of track dropouts into a frame built with verticals. Does this mean you have to buy a special frame or modify an existing frame if you want to lose all but two of your sprockets? Nope.
Go out and find a serviceable old frame that is the right size and that has decent single track geometry. Rigid or suspended, doesn't matter. Rigid is cooler, and it will really make you appreciate your suspension forks after you ride it hard. There are a lot of out of vogue frames like this out there rusting away. Vertical drop outs are just fine.
I "happened upon" an old frame of ours that was set up for a rigid fork and an ancient (but amazingly light!) brazed unicrown fork set up for a big frame. I cut the threads off the steerer and it was still long enough to use a threadless headset. It's a little too modern, but I am dabbling in modernity these days I guess. I can always say that it's because that's all we had laying around in the sample pile.
How do you get away with the verticals??? Coming right up.
You need to get a crank of some sort. An older MTB triple is fine. Think of all the older LX 5 bolt cranks that are accumulating as the trendy new 44/32/22 removable spider, 4 arm cranks hit. These older cranks are perfect.
Long arms are good in the hills. Shorter arms let you spin better on the flats. The best crank length for you depends on where you live and how you ride (and what you find in the pile - you can always make up some story about why it's best after you get them...).
You have a couple of options for hubs. An old road hub works fine. If it's threaded, you will need to re-space it so the flanges are about centered and the over locknut distance is dialed for your frame (135mm normally) and the chainline is about right. You'll need an axle. If you use the middle ring on the crank in it's normal position you should be able to work out the chainline pretty well.
BMX hubs work great with a little axle length and spacer tuning. The ultimate, deluxe units have threading on both ends of the hub. One side is smaller than the other. The smaller threads let you put smaller freecogs on the hub - down to 14 teeth. The normal lower limit for BMX freecogs is 16 teeth. More on this later. You can switch the axle on one of these to a hollow unit so you can use a QR too.
If you can only find old freehubs, no sweat. Bust up an old cassette and pick the cog you want. Use the spacers out of the cassette to center the cog where you need it. Lock it all down. You may need a few more spacers than you can get in one old cassette, but shops have dead cassettes laying
Tensioning the chain
Now for the tricky part. You can use verticals if you use a chaintensioner. And, there are some very nicely machined accessory units out there just for this. But, if you are sly, you will note that any old derailleur fits the bill perfectly! Pull the chain real tight so it doesn't slap or fall off in the bumps. Silence is one of the big benefits of a single speed. It lets you hear your heart pounding and knees creaking as you struggle up hills that are too steep for the gears and even lets you hear the sounds of gushing blood in your brain on a real good day!. Cut off an old cable, pull the end up into the barrel adjuster on the derailleur. Clamp the other end in the cable clamp on the mech, and use the barrel adjuster to center the jockey pulley on the single cog. Chainline tuned!
The manual transmission option
Okay, now for the second, real tricky part. When you use a derailleur for a chain tensioner, you can use more than one gear combination! This departs from the true single speed and I deserve the fate of a heretic, etc... The One and Only True Believer Jihad of the Single Speed will strike me dead one day no doubt. [Witnesses' report: It was weird. His heart burst on a climb - one that he does all the time. There were strange humanlike sounds coming out of the trees too - and he was screaming "No no, I didn't mean it. I was just kidding! Ahrrrggghhh!!!" - we didn't see it happen but it must have been awful by the twisted look on his face."). But in the mean time, I'll jabber on about it. Nothing left to lose I guess. I think the combination rules.
Imagine what is possible if you leave the granny gear on the crank. You can reach down and drop the chain onto that twiddle ring and get up that steepass technical hill you couldn't do on the 2:1. You have a chain tensioner!
Go for what you like or can find. Keep it light if you ride in the hills. Otherwise, no big deal. Use old stuff whenever you can. Don't pay for it if you don't have to. Live by the Schwag Rules. If you haven't heard of these before, here they are:
Cantilever brakes will be easy to find. We happened to have an abundance of XT V brakes that no one like to ride with because they rattle and squeal. Lucky me. Otherwise they work great.
Bars should provide lots of out of the saddle leverage. Lots. Rise bars or wide flat bars and bar ends are a good thing!
Bontrager OR Race rigid - old stock manufacturing and pain blem
any decent hardtail
Bontrager brazed Unicrown - old stock - unsellable
suspension or rigid - it just has to be sturdy enough to ride
Tange 1" threadless - used
anything that fits the frame
Bontrager race lite prototype
Bontrager FS protoype
anything that fits your butt
Bontrager Crowbar Race 13 degree prototype
lots of out of the saddle leverage and something good for technical work
Noname Taiwanese prototype 12 cm
Shimano XT 1 finger - used take off
whatever works with the brakes
Bontrager Foam - samples
whatever fits your hands
Shimano XT V brake - used take off
whatever you can find - good cantis are laying around everywhere
Shimano UN 52 107 mm - new
has to be good and cheap
Bontrager Comp Prototype
lucky me - anything that has the length you need, preferably with rings installed
Shimano LX 4 arm 32 tooth - leftover from crank tests
??? 4 arm 20 tooth - ditto
an old Rohloff sample that didn't work on Shimano IG cassettes - these are the best chains in the world - lucky me
anything - inexpensive Sachs chains that don't shift on a geared bike are perfect for a single speed
15 tooth/18 tooth - new
old Sante road derailleur - hosed
if you have to buy this you aren't trying
very used XT 32 hole
GT BMX 36 hole sealed bearing respaced - laying around
15 gauge - new
used spokes are not a good idea if you build wheels
BCX Red label 360 gram 32 hole blem
lucky me - score a used wheel for the best deal
BCX Red label 360 gram 36 hole blem
lucky me - ditto
Revolt SS prototype
old takeoffs are fine
Revolt SS prototype
lite presta - new
old tubes with patches don't weigh that much
Curve 171 mm 5arm test sample
for a spin machine
ALT FRONT HUB 1
Formula sealed 32 hole sample
ALT REAR HUB 1
32 hole Sanshin road - respaced
the cheap way to go
ALT REAR HUB 2
Bullseye 32 hole BMX - rescued from old frame factory
not the cheap way to go, but it builds the strongest wheel known to man