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Mountain bikers realised early on that hills are much more difficult to tackle with a single-speed bike than with a wide gear range. Limiting yourself to a single sprocket on the rear wheel significantly increases the risk of ending up with too heavy a gear on the uphill or too light a gear on the downhill.
However, it was not until the early years of the original "Klunker" bikes that the technology was available to change several gears on a mountain bike. It was not until 1982 that the Shimano XT, the first MTB-specific gear shifting system was launched on the market, which - by the standards of the time - was stable enough to be used in rough terrain. In 53 years of mountain bike gears, many things have clearly changed for the better in terms of materials. So why is the singlespeed movement not dying out?
Simply simple
Dirt bikers and BMXers have never needed many gears. Without a rear derailleur that sticks out from the bike, without a gear lever that clings to the handlebars and without cables that have to run along the entire length of the bike, a single-speed bike offers fewer opportunities for a defect.
No battery that needs to be charged, no wearing parts that cost money, no annoying rattling because the setting isn't right: Single speed bikes are extremely uncomplicated to use. Simple and robust - these are the characteristics that mountain bikers want from their sports equipment. Ultimately, they can only be achieved with a singlespeed bike. A means of transport driven by two cogwheels connected by a chain is purist, simple and efficient.
Less mass
For singlespeed bikes, not only does "what's not on it can't break" apply, but also "what's not on it doesn't weigh anything". Singlespeed drivetrains also have to be robustly constructed in order to remain durable. However, you save the weight of the rear derailleur, trigger, cassette and, if necessary, cables.
However, the single-speed concept is not only found on lightweight hardtails, but also at the other end of the food chain, namely on some freeride and downhill bikes. As gravity bikes are not used to gain metres in altitude anyway, they save around 400 grams of unsprung mass on the rear wheel.
In theory, this reduces the bike's resistance to suspension movements and thus increases the efficiency of the suspension. Up to 15 per cent of the total unsprung mass is accounted for by the drivetrain. Single-speed fullys can therefore benefit from more grip thanks to a better functioning suspension.
The focus is shifting
If mountain bikers cannot shift gears, the question of choosing the optimum gear is no longer necessary. Single-speed bikers report an improved focus on the best line and a cleaner riding style on the downhill.
If you can't accelerate your bike efficiently by pedalling in every situation, you are forced to pay attention to a clean technique in order to lose as little momentum as possible. For example, Aaron Gwin's run at the Downhill World Cup in Leogang 2015, where the American rode to the podium without a chain, remains unforgettable.
On tours, the focus on a singlespeed bike is not only on maintaining speed, but also on pedalling. Without adapting the gear ratio to the speed, riders have to switch to pedalling in the cradle more often on climbs and ride at a high cadence on descents.
If the focus is shifted from the correct gear selection to the pedalling, a new riding experience will emerge in the medium to long term. Many singlespeed riders appreciate their special sports equipment for the meditative effect of changing their pedalling habits.
How it works
On most mountain bikes, the rear derailleur acts as the chain tensioner. If this is omitted on a singlespeed bike, a different way is needed to keep the drivetrain under tension. Without tension, the chain does not run reliably on the teeth of the chainring and sprocket. There are three options for tensioning the chain without a rear derailleur:
1. chain tensioner
The spring-loaded pulleys can be fitted to any derailleur hanger. High-quality models have an option to adjust the chain line. Because the pivot point of most full-suspension bikes is not in the centre of the bottom bracket, the chain length changes when the suspension is compressed (with the exception of a few slopestyle full-suspension bikes), so a chain tensioner is the only option here.
2. horizontally adjustable dropouts
A widely used option for varying the chainstay length is adjustable dropouts, which are clamped to the frame using solid bolts. Mostly found on classic hardtails.
3. eccentric bottom bracket
Due to the off-centre position of the bottom bracket in the frame housing, the chainstay length changes by rotating. If the bottom bracket is rotated towards the front, the chain is tensioned. The eccentric is usually fixed with two bolts on the underside. The absence of a classic derailleur hanger/ dropout makes a particularly clean look possible. Special single-speed frames with an eccentric bottom bracket are available from Sour, Veloheld or Niner, for example.
The singlespeed hub
In contrast to a fixie hub, a singlespeed hub has a freewheel so that the rider does not have to pedal permanently. Theoretically, all hubs can be ridden singlespeed with the appropriate adapters. With classic HG freehub bodies made of aluminium, it should be noted that individual sprockets can work their way into the material over time due to the one-sided load and damage the hub. There are now also adapter kits for freewheels according to the Sram XD standard, whose screw connection promises a longer service life.
Special singlespeed hubs with steel freehub bodies for mountain bike use and with a Boost installation width are available from Chris King, Hope, Noa or White Industries, for example. They are designed for the loads of a single-speed drivetrain and usually allow for smaller sprockets. Caution: Not all sprocket size options can be realised with all hubs and, unfortunately, high-quality singlespeed components are not cheap.
The right translation
If bikers decide on a single gear, they should make sure that it is suitable for as many riding situations as possible. You can try this out on a conventionally geared bike: Simply engage the potential gear ratio and test different gradients and inclines. For mostly flat commuting routes, for example, a ratio of 32 teeth on the chainring to 13 teeth on the sprocket is recommended. For real off-road use, the ratio should be smaller (about 34 to 18). Special singlespeed chains are designed to be extra tough.
Additional equipment
Many singlespeed bikes use a rigid fork instead of a suspension fork. By their very nature, singlespeed riders often have to ride in a pedalling position, which rules out bobbing suspension elements. In addition, a rigid and therefore lightweight and maintenance-free fork plays to the strengths of a singlespeed bike.
They are not usually used on trails, but rather on flat to undulating rides on gravel and forest paths. To improve the aerodynamics on a single-speed MTB without a drop bar, so-called inner bar ends are ideal.
I'm a big singlespeed fan and use my single-speed bike not only for commuting but occasionally even for 300-kilometre day rides and bikepacking trips. It's as clear as mud that biking without gears is an absolute niche. However, cycling enthusiasts should definitely give the monogamous relationship with a sprocket a try. - Jan Timmermann, BIKE editor
Jan Timmermann
Editor
