The step beyond singlespeed is fixed wheel. Fixed wheel bikes are for track and skilled road use only. They are similar to singlespeeds in that they only have one gear – a single sprocket at the back and a single chainring – but there is no freewheel in the back wheel. This is the ratchet that you can hear ticking along when you coast without pedalling on a normal bike. Riding fixed wheel means you have a really direct connection between the pedals and the back wheel and can control the speed of the bike very precisely.
You can slow the bike down just by pedalling more slowly. This feels odd at first. It’s very much like pedalling forwards, but you have to put pressure on the pedal when it’s at the back of its stroke, rather than the front. Riding fixed takes some practice to do safely as there are a few quirks that can catch you out.
It’s often said that, once you learn to ride a bicycle, you never forget. Riding fixed, you have to deliberately unlearn some of the most basic lessons. The trickiest is that you cannot stop pedalling – the wheel will keep on spinning and the pedals are directly connected to it, so they’ll keep moving. If you tell your feet to stop, the pedals will catch them and drag them forwards, jerking you with them. This is unsettling – a bit like thinking you’ve got to the bottom of a flight of stairs and then finding that there’s another step. Cornering is another problem area. Cornering at speed usually means leaning into the corner. If you’re on a normal bike which freewheels, you can stop pedalling and lift the inside foot up to stop the pedal scraping on the ground. On a fixed model, you can’t stop pedalling so you have to judge corners very carefully, otherwise your pedals will slam onto the ground as you lean into the corner and flip you off the bike.
As well as going along and cornering, there’s another potential problem as well – stopping. Fixed wheel bikes were inherited from track racing, where fit people on sparse track bikes hurtle round banked wooden tracks at unfeasible speed in the kind of tight bunches that means it’s in everybody’s interests to stay upright. Brakes in this situation are a liability – as long as everybody is moving at the same speed, there’s hope of keeping your place in the pack. The last thing you want is for the person in front of you to panic and haul their brakes on. The gaps between each rider can be inches and there would be no time to take evasive action. Bikes that have been built for the track may not have brakes at all or, if they do, they’ve just been stuck on there to make the bike legal to sell.
Transferring the bike onto the streets involves different demands. Your biggest danger is a truck turning left in front of you, not the potential for inadvertently bringing down somebody riding right up your tail, so it’s essential to fit some properly working brakes. Many people make do with just a front one, because you can use the pedals to slow the back wheel down. Some riders take it to the extreme and have no brakes at all, relying on controlling the speed of the back wheel alone to stop them. This is just stupid. It does make the bike look lean and mean, until you wrap it around something you should have been able to avoid. It may then still look pretty if it was a nice colour to begin with, but it won’t work very well. Fit proper brakes.
“Your pedals will slam onto the ground as you lean into the corner and flip you off the bike”
You can buy singlespeed road bikes fitted with a fixed rear hub (or a ‘flip-flop’ hub, fixed on one side and with a freewheel on the other, simply take the wheel off and flip it around as necessary) off the shelf (or from several internet retailers) or make one by removing all unnecessary complications from a (usually old) geared bike. The one essential requirement for a conversion to fixed wheel riding is horizontal dropouts for the rear wheel. Since most modern frames are built with vertical dropouts, this restricts you to old road frames, and newer frames that have been specifically designed for singlespeed riding.
It’s essential to use the right kind of hub with fixed wheel. As well as a normal, right-hand thread for the fixed sprocket, it also has a slightly smaller reverse thread. This is for the lockring. The lockring must be tightened securely against the fixed sprocket, stopping it from unwinding when you put pressure on the pedals to slow down and stop. It’s essential that the threads on the fixed sprocket, the lockring and the hub are in good condition, so that there is no possibility of the sprocket working loose under the constantly reversing pressures from your pedal. Don’t be tempted to make up a fixed hub out of a normal freewheel wheel and any likely-looking lockrings you may have lying around – the reverse thread on a fixedspecific hub is essential for holding everything safely together.
It may seem from this that riding fixed is anachronistic and more trouble than it’s worth, but it does feel fantastically direct and makes any journey more exciting.
Source : BIKE MAINTENANCE TIPS, TRICKS & TECHNIQUES
See also bike maintenance tips, tricks and techniques “Single speed riding for getting about”