Cycling
Single Speed Riding Works Until the Ground Stops Being Flat
One gear removes the parts that go wrong and the choices you have to make. It also removes every option you had on a hill.
There is a short answer about single speed riding and a useful one, and they are not the same. What follows is the useful one.
The short version
- Removing gears removes cables, adjustment and the parts that bend.
- One ratio means the cadence changes instead of the effort.
- Terrain, not preference, decides whether one gear works.
What actually gets deleted
A single speed drivetrain has no shifters, no cables, no derailleurs and no cassette, which removes most of the components that need periodic adjustment. The chain runs in a straight line between one chainring and one sprocket, so it does not have to bend sideways to reach anything. That straight chainline reduces the sideways wear that eventually turns a chain and cassette into a skipping mess on a geared bike.
There is no rear derailleur hanging low behind the wheel, which is the part most likely to be bent by a fall or a badly parked neighbour. Fewer components does not mean no maintenance, since the chain still wears, the bearings still need attention and the brakes still matter more than everything else.
What replaces gear choice
On a geared bike a change in gradient is answered by changing gear and holding roughly the same pedalling rhythm and effort. On a single speed the ratio is fixed, so a change in gradient is answered by your legs turning slower and pushing harder.
Come the wet months, that is fine across a modest range, because the human body tolerates a fairly wide band of pedalling speeds without complaint. Beyond that band the options run out, and you are either grinding at very high pedal force or spinning uselessly fast downhill. Grinding is the one to avoid, because sustained high force at low cadence loads the knee joint far more than the same work spread across faster, lighter strokes.
Choosing the one ratio you get
The single decision on a single speed is the ratio, and it should be set by the hardest part of your regular route rather than the flattest. A ratio that climbs your worst hill seated will feel slow and spinny on the flat, which is a mild annoyance rather than a problem.
A ratio that is comfortable on the flat may simply be unrideable on that hill, at which point you are pushing the bike. Changing the ratio means changing a sprocket or chainring, and often the chain length with it, so it is not a decision you revisit mid-ride. Riders in genuinely flat cities converge on ratios that would be laughable in a hilly one, which is the clearest evidence that terrain decides this.
Fixed and freewheel are not the same thing
A freewheel single speed coasts like any other bicycle, with the pedals staying still while the rear wheel turns. A fixed drivetrain locks the pedals to the wheel, so if the wheel is turning your legs are turning, with no option to stop.
By the second week of riding, that connection gives a direct feel and allows speed control through the legs, which some riders find genuinely pleasant on flat urban roads. It also means you cannot stop pedalling to take a hand off, and a moment of inattention over a bump can throw you off rhythm.
A fixed machine should still carry a working brake, and in many countries a brake is a legal requirement regardless of drivetrain, though the details differ by jurisdiction.
Chain tension and the thing that goes wrong
Without a derailleur there is nothing taking up slack, so chain tension is set by moving the rear wheel back in the dropouts or by an eccentric bottom bracket. Too loose and the chain can climb off the sprocket under load, usually at the worst possible moment while accelerating away from a junction.
In the saddle, too tight and you are loading the bearings continuously, which wastes effort and shortens their life without any benefit. The target is a small amount of vertical movement in the chain at its tightest point, checked by rotating the cranks through a full turn. Sprockets and chainrings wear into a shape that only matches a worn chain, so replacing a stretched chain onto old teeth often produces skipping.
Range and charging figures are quoted under conditions nobody commutes in.
Who it genuinely suits
Riders in flat cities with short journeys and secure parking get most of the benefit and pay almost none of the cost. Riders in hilly places, or anyone carrying children and shopping, will find the missing low gear becomes the defining feature of every ride.
Come the wet months, it is a good winter machine in wet places, because there is less exposed mechanism for grit and salt to attack. It is a poor choice for anyone with knee problems, because the drivetrain removes exactly the adjustment that protects the joint. The simplicity is real, but simplicity that forces you into high pedal forces is a trade rather than a free gain.
The takeaway
One gear is a lovely idea in a flat city and a daily argument in a hilly one.
Most of riding well is being boring and predictable to everyone else on the road.
Questions readers ask
Is single speed bad for your knees?
It can be, because the fixed ratio forces high pedal forces on climbs where a geared bike would let you spin. If the ratio suits your terrain and you rarely grind, the risk is much lower. Persistent knee pain is a reason to see a clinician.
Can I put a single speed on a hilly commute?
You can, but the ratio has to be set for the steepest climb, which leaves you spinning out everywhere else. Most riders in hilly cities find the compromise unpleasant enough to go back to gears.
