Building a SingleSpeed

The Frame

There are a couple of approaches to getting a SingleSpeed up and running as far as the frame goes.

1. Money No Object - buy a specific SingleSpeed Frame.

2. Get a cheap (or expensive ?) steel frame and get some track drop outs attached by a frame builder.

3. Buy a SingleSpeed chain tensioner - or use the limit screws on a rear mech. so it doesn't shift.

4. How to make a chain tensioner from an old mech. See Below

There are now quite a few manufactures producing SingleSpeed frames - Santa Cruz, 1*1, Spot, Bianchi, Voodoo etc. In addition some of the current crop of Dual Slalom bikes which would suffice try Azonics or DMR.

The one thing in common with all these frames is the rearward facing drop outs - in other words the rear axle can move closer or further away from the bottom bracket - allowing you to tension the chain.

Aside from that pick whichever frame suits your size and pocket as you would a normal MTB.

Wheels

Again a couple of choices - it is perfectly possible to convert a normal 7 or 8 speed into a suitable SingleSpeed rear wheel - simply by using the spacers which come with a cassette. Have a word with your Local Bike Shop (LBS) they probably have a box of them from old bikes. The advantage of this is that you can change the gear ratio pretty easy, and by juggling the spacers round it is easy to get a good chainline.

Or you can get a BMX rear hub, remove the axle, replace it with a MTB axle and add some spacers. Wheelpro can make you one of these up, and very nice they look too.

Or for a little more money you can get a SingleSpeed hub and get a wheel built up from it. Plenty of manufactures can sort this out for you. Hope, Pauls, Spot, 1*1 etc. I'm running a Hope and its loverly. Then you get the obligatory Shimano BMX freehub and sprocket and your pretty much done.

The advantage of the last one is the weight saving - pick up a normal rear wheel and compare the weight  with a front wheel. Some difference eh ? Well, with a SingleSpeed your rear wheel only weighs about 2/3 oz more than the front (Ha-Ha-Ha-Ha !)

If you are using an MTB hub you can either replace the axle with a solid axle and locknuts or tap a 6mm thread and use 2 bolts threaded in. This will allow you to lock the wheel tighter than a quick release ever can.

Also buy some chain tensioners which make it nice and easy to pull the chain to the right tension - rather than the hit and miss way it ends up without them.

Cranks

Get some very strong cranks.... You will be using all your effort to get up hills - putting an incredible strain on all the transmission parts. The mags. say longer is better  - as you get more leverage, I'm running 175mm at the moment - but with the B/B I've got I can't change them, mind you I can get up just about anywhere I want... If you want longer cranks  plenty of suppliers make them, Spot, Middleburn etc. Shortly after I typed this I destroyed a set of bullseye cranks.... 

Tyres

The mags say get a meaty rear tyre so you don't lose traction on rocky climbs. I'm running a very slender 1.9" semi-slick - why ? 'Cos its way light - which allows me to 'skip' the bike up climbs. When the weather turns worse I'll probably go for a 2.1" Velociraptor. 

Bars

Good and wide... A nice set of riser bars gives you loads of leverage when the trail turns upwards. On a SingleSpeed strength is more important than weight, so go for a good brand - and not the XC variety..

Gear Ratio

The size of the chainring is very important - a typical chainring will be a 34 or a 36 - double the amount of teeth on the front than the back to give a 1/2 ratio. 1 turn of the cranks gives two turns of the back wheel, or for each leg you push down you go forward one rotation of the back wheel (approx. 2 metres). 32 teeth rings are available from Middleburn to special order (and in a range of colours)

The freehub on the back should be therefore be a 16/17 or a 18.

Listed in one suppliers catalogue we spotted a 13 tooth BMX freehub. this would allow you to run a 26 on the front, so if your chainline would allow it you could run a 26th granny ring rather than the 34 or 36 middle ring. This would give you miles of ground clearance !

Of couse what works for you might be different due to local conditions, if its way hilly then try a slightly different ratio, like a 32*17, or even a 32*18. If its flat where you are then see what you can get away with. Anyone running 1*3 ? (48*16) ?!?!?

Chain

The mags say use a BMX chain, but if you are using an MTB chainring the chain does not fit quite right (according to my LBS who sell both) and you will wear your chainring and chain out much quicker (I stand to be corrected on this point) I have a normal XT type chain on with a split link instead of the jointing pins. There have been a couple of occasions where I have expected to break it, but haven't so I'll probably stick with it.

Chain Tensioner

Ok - not everyone has or can afford a frame with horizontal dropouts to tension the chain, so what other options are there ?

Well, you could leave the rear mech on and centre it using the limit screws. The only problem is that the limit screws probably won't move the mech far enough to keep it in place, the good news though is that they are a standard size that you can replace easy enough with longer bolts ! Take them out, take them to your LBS, or local engineering supplier and they will probably have some with the same thread  - I was going to post the size here, but then remembered that the ones my mech take may not be the same as yours....

If you want something a little different you could try a singulator available from your LBS, or try this link...

Or..... You could make your own ! This is so cool it even impressed my LBS manager - and he's an ex-engineer !

I'm going to do a photo series on this on my page shortly, but for now here is 'How to make a funky tensioner for free !'

I had an XTR mech that I'd unfortunately destroyed the cage and lower jockey wheel on - for some reason I'd kept it since I broke it about 6 months ago, but just about any mech will do as long as it still has a top jockey wheel

1. Remove the side of the cage that would be nearest the spokes (left hand side looking at it from top down) and both the jockey wheels
2. Cut the remaining side of the cage just below the top jockey wheel and file off all the sharp edges (a grindstone saves time with this - but ask you parents first LOL)
3. Replace the top jockey wheel and loctite the screw into place. It doesn't need the left hand side of the cage, the wheel will rotate quite happily without it.
4. Remove the limit bolts and replace with longer bolts - I happened to have two from a Mr Crud front mud guard, but your lbs will probably have something similar for next to no cash.
5. Bolt back onto bike and run the chain over the bottom of the jockey wheel and round the rear sprocket. Make sure the chain is pretty tight and the mech almost horizontal, if its not the angle the chain takes is not sufficient to stop it jumping under load.
6. Adjust the limit screws so the mech is in line with your rear sprocket and go shred !