A single-speed bicycle is a kind which has a single-gear ratio. Gear ratio is the connection between the number of teeth on two gears, meshed with each other. It is two sprockets linked with a single roller chain. There are usually two types of gears in bikes, derailleur gear and hub gears. But these single-speed bikes do not have these gears. Moreover, in single-peed bikes, there are various types, like mountain bikes or trek bicycles, road bikes, hybrid bicycles, and so on. The parts are fixed in such a way that they allow coasting through its free-wheel mechanism.
Weight: This is good news for those who are ruminating about which bike to buy. One of the most appealing advantages of a single-speed bike is that it is lightweight as compared to a geared bicycle. This is thanks to the absence of derailleurs and hub gears, which are normally found in multi-speed bikes. A few other parts can be made stronger too, without making the bike too heavy.
Maintenance: Lesser accessories means less maintenance, and that is a huge relief for owners. Who would not want low bills for maintenance! The tires are also sturdier, and replacing gears and other parts is not a major hassle, again, on account of derailleurs.
A reason why bikers go in for single-speed bikes in winter, is because the drive chain of a single-speed can endure wet, muddy, and gritty conditions, unlike normal geared bikes. If normal geared bikes have to go through this, their components, which are expensive too, will wear out. This will obviously lead to high maintenance costs.
Cost: This bike is not just light in weight but light on your pocket as well. Single-speed bikes are significantly cheaper than their geared counterparts. Be it buying or assembling one, they definitely save you a good buck or two. Moreover, you will not compromise on the strength and efficiency of the bike.
Drive Train Efficiency: Now, as compared to geared bikes, the drive train efficiency of the single-speed bike is much better. The derailleur is not present in this kind of bike. This reduces the drag in the chain system, typically associated with derailleur's jockey pulleys. The chaining and cog of these bikes is in such a way that it lags behind on ramps and pins, which adds to its advantages.
Sentimental Value: Although this is not admitted by those who ride single-speed bikes, it is a fact. The idea and the knowledge that their bike is different from run of the mill geared bikes is something which they cherish. Moreover, they get that high, that even without sophisticated gears, their bike can ride on the same roads and difficult terrain. Plus, it is a great workout method, and develops and tones your leg muscles in lesser time.