How to Build Your Own Single Speed or Fixed Gear Bike:
After years in the wilderness (about 18 I reckon) I bought myself a bicycle and actually “got into” cycling. Which was odd because I was never bothered before, even when I did own a bike. However, I’ve found it to be great fun, a useful form of transport as well as good exercise.
Not long after buying my bike I read in a magazine about single speed bikes and wondered what the point of it all was. After all I had my 18 speed bike (which is pretty old fashioned - most decent bikes seem to have 27 gears these days), why would anyone want something with only one gear. From a quick search on the internet it seemed that most people had similar thoughts, with single speed bikes being dismissed as a fad.
I soon found out why people wanted single speed bikes when my front deraileur trapped the chain, twisted it and then with minimal force it snapped. On top of that there were the clunky shifts when the chain was under tension. And that the chain would jump off the front sprocket if I switched the front chain ring from the middle to the granny ring with even the slightest amount of tension in the chain. I now realise that a lot of these problems were down to me having bad technique, but they’re pretty common problems to a lot of newbie cyclists.
Basically, my new found cycling wonderfulness was under a lot of question. I can happily wield the spanners in anger - I need to fix my motorbike enough - but cycling was more fun when I didn’t end up with grease covered fingers because the chain had decided to jump off the sprockets every time I went over a bump in the smallest sprocket.
Surely there had to be a solution to this stupidity. And then I read of hub gears. They sounded good. If I were to be honest anything that wasn’t a deraileur sounded good. Unfortunately hub gears all seem to be horrendously expensive, so that idea bit the dust.
And so the idea lay dormant for a while. I just kept on cycling more and more. Eventually I got bikes with better derailuer setups that were more reliable and shifted more cleanly and easily than the old bike (Campagnolo deraileurs are particularly good for this), but even they went out of adjustment eventually and needed some attention.
However, all the cycling had been paying dividends. My legs were getting a lot stronger and I was finding that I was using less and less gears, especially around town. So one week I thought I’d stick it in a particular gear and leave it there. And sure enough I managed perfectly well around Manchester. And so the plan was hatched to hack the gears off my crappy old bike and make it a single speed in time for winter.
Ingredients
- a kona smoke (this particular one is somewhat nonstandard, with an upgraded crankset and front derailuer, new bottom bracket, rack and longer seatpost).
- single sprocket crankset
- chain tensioner
- single sprocket and spacers
- BMX chain
Recipe
- First of all the rear derailuer came off
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before |
after |
- That was pretty easy. Just slacken the cable on the derailuer and pop the outer cable out of a cable stop. Once that was done it was easy to take the cable out of all the other cable stops. Then unscrew the deraileur.
- Next up the front deraileur came off.
Pretty similar to the rear. Undo the cable, pop the outer cable out of a stop and then take off the whole cable and the deraileur itself. Before you know it your seat tube will look all sleek and clean. Like this:
- Next up is to get rid of the heavy chainrings. They’re going to be replaced with another chainset that weighs a fraction of the crappy sprocket ridden crap.
- Then the rear cassette was taken off.
- Now to start putting the new bits on. First of all the new chainset.
- Then the spacers and the new, 16 tooth, sprocket.
- Next up was the chain. It didn’t fit exactly so it had to be fit to the next link. It was still rather slack, so the next thing to do was…
- fit the chain tensioner. At this point it was obvious the tensioner wasn’t the best thing in the world. It was impossible to fit or remove the wheel without almost completely removing the tensioner. Not exactly ideal.
- With the wheel fitted again the tensioner was fiddled with to get the chain tension right.
And then that was it finished. Dead easy. It only took half an hour. And this is the finished article:
Testing
The next job was to test it all. So along the street I went and the problems started to appear. First of all there was a steady clacking noise. It turns out the chainline wasn’t quite right. It had been hard to notice before because it only came up when the chain was under a decent amount of tension.
So the rear sprocket came off and the spacers were fiddled with. Then there was another test ride. It still wasn’t right. At this point I cheated and asked myself “what would sheldon do?“. Turns out I had a ready supply of spacers lying around in the form of the old gear cassette.
So that got hacked apart (with a masonry chisel and a lump hammer) and became a handy supply of spacers of various widths. The plastic spacers between the sprockets were fairly thick, but the sprockets themselves worked nicely as shims to get the chainline spot on.
The next problem that popped up was with the chain tensioner. It was pretty much impossible to get the surface of the roller at right angles to the chain and when the chain passed over the roller it was being forced off to one side or the other. On top of that it was a real pain to get the real wheel out. The only way was to remove the tensioner completely every time - not ideal.
Chain tensioner II
The original chain tensioner was causing tons of problems. The chain would keep moving around the roller and locking up against the sprocket. It just wasn’t working at all. So I bought a different tensioner.
This one was much better. It is spring loaded so it automatically sorts out the chain tension. The derailler jockey wheel on it is a lot more forgiving when setting up the chainline. And For that matter setting the chainline is significantly easier. And it’s much easier to remove the rear wheel.
It solved all the problems of the original chain tensioner. The only downside was that because it pulls the chain down instead of up the chain doesn’t wrap round the rear sprocket as much. Which didn’t seem as much of a problem at the time…
15 tooth sprocket
With the new tensioner the bike was finally usable. So after a few test rides it was time to hit Manchester. That’s where the new problems appeared. Basically, the chain was about half a link too long and there was a lot of slack in the transmission. So much that it was very easy to get the chain to skip round the sprocket. Obviously this was down, at least in part, to the new tensioner not wrapping as much of the chain round the sprockets as the first tensioner, which pushed the chain upwards instead of downwards.
To begin with it only happened accelerating away from traffic lights. Then it skipped going up hills. Eventually, after a few days, it was happening just about all the time.
So when I got to work I popped the rear wheel out and had a look at the sprocket. It wasn’t looking too happy.
Although it’s not easy to see on the photo, there’s a few bent teeth and the metal at the base of the teeth is distorted. It’s just a mess really.
So off I went and bought a nice new rear sprocket. Instead of a cheap and crappy pressed steel thing I got a nice CNCed steel sprocket. This time with 15 teeth instead of the 16 on the old sprocket. It was a hell of a lot nicer. See:
How nice does that look? It’s lovely.
Anyway, It fitted better than the last sprocket (needed less spacers because the base of the sprocket is wider) but a new problem came up. The one extra tooth meant there was more slack in the chain. I was pretty sure I’d have been able to drop a link and get a good, taut, chain but it turned out there was about 3/4 of a links worth of slack.
Because of this the chain was jumping a lot more than it had been. It was quite painful really. Anything more than the slightest acceleration lead to a nasty *clunk* *clunk* *clunk* as the chain jumped over the sprockets. So that needed fixing, which lead to…
half link chain
The solution to having to tighten the chain a bit was pretty obvious. I should take my steel frame to a frame builder and get track ends fitted. That would be the perfect solution but not the most practical solution - to get a half link.
The usual source of half links everyone on the net mentions is St John’s Street Cycles. They have them in both 1/8″ and 3/32″ sizes, and are really an excellent company to deal with (I bought a bike from them and the chap in the shop happily spent 2-3 hours making sure I had the right size and that it was specced out sensibly for what I wanted it for). The only problem is that the 3 quid postage charge seemed a bit crappy for a tiny half link.
So in a fit of complete and utter non-logic I instead bought a strangely named reluctant half link chain from chain reaction cycles which cost twice as much. But at least it meant I didn’t have to break the old chain, which would have been getting a load of dodgy links with my attempts to lengthen and shorten it so it would fit. If I were honest though, the main reason I bought that over a single half link was that it just looked better. In a strange way it looks like it’s made from fish scales, all shiny and overlapping.
Anyway, that went on with a load of hassle (which broke my chain tool) and fitted pretty much spot on. It almost didn’t need the tensioner, but in the end there was just a little too much slack, and I put the tensioner back on (one handy feature of this particular tensioner is that you can easily put it on with the chain fitted - you don’t need to route the chain through it before fitting).
The finished product
With the half link chain on everything worked just fine. The chain didn’t skip at all. The tension was good. The chainline was pretty much spot on. It was all happy.
With a transmission giving 72.1″ of gear inches (5.4 gain ratio) it can be a bit slow to accelerate from a standing start, but once it’s past walking pace it’s a doddle to accelerate to a decent speed (I don’t know what sort of speed; in keeping with the minimalist nature I don’t have a speedo) - enough to keep up with cars around town.
The final incarnation of the drivetrain seems to work pretty well. I suspect the only improvement I could make would be to swap the frame out for one with track ends but then I’m not sure if it would be this bike any more. It would be like a whole new bike, and at the moment I’m perfectly happy with it as it is.
The final part of the conversion: me
To begin with I was only going to use this bike around Manchester. It’s all flat round there so the lack of gears wouldn’t be a problem. But then one day I used it to climb one of the local hills. More by accident than anything. Since then I’ve used it more and more and reaped the benefits. With the only way to get up hills being brute force I’ve become a lot stronger. This has spilled over onto the times I’ve ridden a bike with gears - I don’t change gear as often and find it easier to muscle my way up hills instead of spinning.
Just about everything about riding this single speed has been positive. Or at least it has been once the initial problems were sorted out. But there’s one more step to go. But for that I’ll need a new frame with horizontal drop outs or track ends. I mean to get myself a fixed gear bike now I know one speed is enough.
“I still feel that variable gears are only for people over forty-five. Isn’t it better to triumph by the strength of your muscles than by the artifice of a derailleur? We are getting soft… As for me, give me a fixed gear!”
–Henri Desgrange, L’Equipe, 1902