Shimano are a Japanese manufacturer of cycling components. They're not just any manufacturer, they are the leading manufacturer - it is estimated that 70-80% of the global bike component market is made up of Shimano products. They make a lot of components. Here we're going to look at gears, in particular, the Nexus 7, Nexus 8 and Alfine 8 so you can choose the best one for you.
Shimano Nexus 7
Shimano’s super-reliable Nexus 7 hub offers all the low-maintenance reliability of the traditional 3-speed Sturmey Archer hub that your grandad used, but with a much wider range and smaller steps between the 7 gears, giving gearing equivalent to an 11-27 7-speed cassette. With a typical chainring and sprocket combination of 40/19 the bottom gear is 36 inches and the top is 88 inches, enough for modestly hilly terrain. The shift is smoother and faster than the old hub gears, and you can change gear at a standstill (no more lifting up the back wheel at the traffic lights!) With no shifting between sprockets, the chain lasts ages, and can be enclosed, and the hub itself needs servicing only every two years or 5000km.
Shimano Nexus 8
Shimano's Nexus Inter-8 hub has all the same benefits but with an extra gear for an even wider range, equivalent to an 11-34 cassette, so better for hillier terrain, although some of the gear steps are a little wider as a result. The same 40/19 ratio gives a bottom gear as low as 30 inches and a top of 92 inches. With sprockets up to 22 teeth available the gearing can be as low as 26 inches, lower than 1:1 gearing on a derailleur equipped bike. Shimano’s precise manufacturing standards mean the hub has very low drag, beaten for efficiency only by the most carefully maintained derailleur gears, and labyrinth seals shut out dirt and water to extend the service life. Inter-8 hubs use pedal power to aid down-shifting resulting in fast and accurate shifts with an exceptionally light feel. Read our blog on Why You Should Consider Nexus 8
Shimano Alfine 8
Shimano's Alfine 8 hub was developed for mountain bike use and is designed to be ultra reliable even in extreme conditions, and Shimano say it’s their most efficient yet. Gearing is identical to the Nexus 8, though it’s only found on disc braked bikes, and shares most of its internals with the recent Nexus 8, with labyrinth seals for weatherproofing, and similar needle bearings for increased durability and high drive efficiency. The Alfine’s top-normal internal structure gives improved tolerance when shifting while riding under load, making it ideal for E-bikes and offroading, while the double roller clutch engagement also gives a smoother quieter shift.