Bikes with hub gears aren't as popular in Britain as those with derailleurs. For commuting, they should be. While derailleurs need regular chain care and occasional adjustment, hub gears tend to run and run without any cossetting.
Gear shifting goes on inside the hub shell, where small pinions mesh together to rotate the rear wheel at a different speed from the sprocket. A hub gear is mechanically more complex than a derailleur, where the chain is simply derailed from one sprocket (or chainring) to a larger or smaller one, but the mechanism is hidden away from rain, grim and hard knocks, and gear changing doesn't depend on the state of the chain. For day-to-day transport bikes, hub gears take some beating. They particular suit roadsters, urban hybrids, and compact folding bikes, but are viable on a wide range of bikes.
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Hub gear advantages
You can shift gears when stationary, going from top gear to bottom while waiting at the lights, making it easy to set off again – particularly if you're heading uphill or carrying luggage.
With one chainring and one sprocket, the chainline is constant. The chain will last longer before needing to be cleaned and lubred – or being replaced entirely. The chain can be completely enclosed in a chain case, reducing chain maintenance further and enabling you to cycle in normal clothes without worrying about oily marks.
Rear wheel spoke breakages are rarer because hub gear wheels aren't dished like derailleur gear wheels. They're symmetrical. This makes them stronger.
Hub gears are simpler to use. Ordinarily, there's one shifter, with the gears numbered from 1 to 3 (or 5, 7, 8, 11, or 14…) There are no 'crossover gears' or duplicate gears: gear 1 is easiest (for climbing), gear 3 (or 5, 7…) is fastest. You don't have to anticipate gear shifts to the same extent either
Any glitches are usually due to problems with the cable tension, which can be adjusted easily at home. The hub itself should go on working for a long time, perhaps with an oil change at the bike shop every year or two.
Hub gear disadvantages
Most hub gears have a smaller range than derailleur gears: the difference between top and bottom gear is narrower. A 3-speed hub is fine on flatter or rolling terrain but can be hard work on hills. A 7-, 8- or 11-speed hub is a better bet there.
The number of gears is smaller than a derailleur setup too, so there are bigger steps between those gears. You can't change those steps. However, you can move the whole range up or (more usually) down. Retro-fitting a bigger sprocket or smaller chainring will make hills easier whatever hub you have. Ask your bike shop about this.
Hub gears aren't as efficient as well-maintained derailleur gears. All those pinions whirring around create friction. A simple 3-speed hub is comparable in efficiency to a 27-speed derailleur set-up. More complex, multi-geared hubs are typically two or three percent less efficient on average, with the greatest losses is in the gears furthest from direct drive. However, the efficiency of hub gears tends not to deteriorate – it may even get better as the hub wears in – whereas derailleur systems that aren’t well maintained get rapidly worse.
Wheel removal is more of a fiddle. You'll generally need a spanner to undo the axle nuts and might need to unscrew a torque arm from the chainstay. The gear cable will also need detatching. When you put the wheel back, it normally has to be correctly located in the dropouts to tension the chain. If you're not comfortable with this, avoid having to remove the rear wheel: check out our advice on how to prevent punctures.
Hub gears tend to be a bit heavier than derailleur gears, and it's noticeable because all the weight is in one lump. This doesn't really matter for commuting.
Inside the hub
Let’s take a 3-speed hub. Its meshing internals are made up of three elements: a ‘sun gear’, which is fixed to the axle; three or four ‘planet gears’, held in a cage and orbiting the sun; and a ring-shaped ‘annular gear’ that encloses the whole lot. Clutches in the hollow axle determine how the drive from the external sprocket gets relayed to the hub shell and thus the wheel.
To get high gear, the sprocket drives the planet gear cage, which turns the annular gear while the latter is connected to the hub shell. For a typical three-speed, the wheel then turns 1.33 times faster than the sprocket. To get low gear, the sprocket drives the annular gear while the planet gear cage is connected to the hub shell. The wheel then turns slower the the sprocket – typically 0.75 times as fast for a three-speed. Middle gear is simply direct drive: the hub internals are bypassed and the sprocket drives the wheel. Confused? The video here may help.
A 5-speed hub is effectively two 3-speeds in the same shell; direct drive isn’t duplicated so you don’t get a 6-speed. A 7-speed might be three 3-speeds in the same shell or two 5-speed hubs driving each other, with only the 'best' seven of 25 possible gears selected. Clever stuff!
How do you compare the range of a hub gear to derailleur gears? First, you need to know how derailleur gears work. A hub gear bike's chainring, sprocket and wheel size will give its direct drive gear. All the ratios are based on this and will be listed by the manufuacturer, for example 0.75, 1, 1.33 for a 3-speed. Multiply the direct drive gear by this ratio to find the size of each gear. If direct drive is 52in, first gear is 39in and third gear is 69in. Not a bad selection for round-town use.
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