Author Topic: Single Speed  (Read 2254 times)

Single Speed
« on: April 08, 2008, 11:08:04 am »
You might notice that a few of my bikes are single speeds (SS). 
First let me say this.  I am making no claims that SS is better than fixed (or vice-versa).  I’ve seen all the arguments for both and they both have good and bad points.  But they are both bikes and we shouldn’t criticise anyone for the bike that they ride, should we?

Why should the bike bodger consider going 1FG?  

Firstly, because it prevents replication of your best bike.  I could have left the gears on my Threatened Fixie, but then I’d have two bikes that were best suited to exactly the same purpose.   
Secondly, because an old skip bike will tend to be a little heavier than a more modern shop bought bike.  Removing much of the drive train helps to redress the balance a little. 
Thirdly, because it’s cheap: your raw skip bike often has rusted up or damaged components and removal is cheaper than replacement. 
Fourthly, because the above are just excuses, the real reason is: one gear is just so much fun.

But why SS over fixed?  For bike bodgers it’s often just a question of cost and ease.  If you are starting with a cassette hub then going SS is cheaper because you don’t need to replace the hub or wheel.  A SS on a cassette hub also makes getting the chain line right a piece of cake.  If however, your wheel has a block on it, then you might prefer to go fixed by screwing on a fixed sprocket and possibly a BB lockring (although there is debate as to whether this is a help or a hindrance).  The problem with screwing on a fixed sprocket is that getting the chain line right might require respacing the hub and redishing the wheel. 

So, you’ve got your shimano cassette hubbed bike – how do you go SS?
Here's a simple and basic guide that should cover the typical 1980s/1990s bike:
1.   Remove gear shifters
2.   remove front and rear mechs
3.   remove gear cable and casing
4.   if you’ve more than one chain ring: remove chain rings until you only have one left – you will either need some shorter bolts now or might get away with reversing the ones you already have.
5.   take cassette off the hub
6.   take cassette apart – there are three pins running through it.  They either have rivet or allen key heads.  If rivet then file down and remove, if allen then unscrew.
7.   Put all of the plastic spacers back onto the cassette.
8.   Select one of the sprockets and put that on the cassette.
9.   Now get a second cassette – an old knackered one will do (loads in the bin at the LBS) and take apart.  Put the plastic spacers from this on to the first cassette until it’s full.  Put the lock ring back on.
10.   put cassette back on wheel and wheel back on bike.  Are the chain ring and sprocket in line?  If not then take the cassette apart and move the spocket along until it is in line with the chain ring
11.   Have you got horizontal or near horizontal drop outs?  If yes then reduce the chain to the correct length and slap back on – finished.  If not then you will need a tensioner or magic gear.  A chain tensioner can be bought fairly cheaply, less than a tenner from e-bay, it screws into the hole for the rear mech, you wrap the chain around the jockey wheel on it and it keep enough tension in the chain to keep it on the cogs.  Or, you could just use your old rear mech – you’ll need to get it in line by threading a bit of gear cable from the clamp, through the barrel adjuster, back over the top of the barrel adjuster and into the clamp.  Then use the barrel adjuster to get the line right as using the Hi/Lo stops doesn’t always work for this.  Finally the magic gear option: here you experiment with different sized chain ring and sprocket until you get one that fits perfectly with not too much slack in the chain and doesn’t make it too tight.  Problems with the magic gear: 1, as the chain stretches you won’t be able to adjust the tension for the stretch. 2, chances are that the magic gear that you find won’t be the one that you want to ride with.

Things not to do:

1.   If you build a SS DON’T remove the rear brake.  Fixies can do this because they can use the cranks to slow down, on an SS you can’t.
2.   If you build a fixie DON’T use a chain tensioner – if you do and you live to regret it you will be lucky.

Of course, you can go full bodge and not bother taking the cassette apart, this means that you have less choice in what gear you ride but it’s less work to build.

What else do I need to mention? 

Chain tension – how much should you have.  If you grab the chain half way between crank and sprocket you ought to be able to move it up and down a little less than around 1cm either way, but at least around 0.5sm either way.

What sized gear?  Depends how strong you are.  For a SS you can ride slightly lower than for a fixie because you won’t need to spin like a demon on the down hills.  Perhaps around 60 to 65 inches is a good starter.

QRs – if you have horizontalish dropouts and a crappy lightweight QR in the rear hub then bin it and get a nice strong steel one.  The extra force going up hills can pull the back wheel out of position if the QR isn’t quite tight.  The steel ones are easier to get tight than the light weight ones.  Or you could fit a chain tug but if it’s a forward facing drop out then you’ll have to shop around to find one that fits.  I got some cheapo HubJub ones and remanufactured them slightly to fit mine.