Anyone who has ridden a bike with a derailleur drivetrain pretty quickly learns when, where, and how to shift smoothly. Mostly it’s a matter of shifting while pedaling, but not while under too much load. Shifting while under too much power can cause mis-shifts and may even cause premature wear on drivetrain components. And, of course, attempting to shift while the pedals are stationary doesn’t accomplish anything; in other words, the chain needs to be moving for the derailleur to do its work of “derailing” the chain from one sprocket to the next. As long as these basic techniques are used, derailleur drivetrains are pretty easy to shift.
The main difficulty with using derailleur drivetrains is not so much the technique of shifting the chain from one sprocket to another, but keeping track of where the chain is running on both the front and rear gear sets, particularly with triple cranks. As most experienced bicyclists know, it’s a good idea to avoid gear combinations that simultaneously place the chain on the inside chainring on the front and the outside cogs on the rear cassette, and vice versa. “Cross chaining”, as it’s called, places unnecessary wear on the drivetrain and may cause mis-shifts and even slippage. It’s perhaps a bit much to expect beginners to keep track of this while contending with traffic, pedestrians, dogs, joggers, and other bicyclists. I know of more than a few novice riders who rarely, if ever, shift out of the the middle chainring on their triple crank for this reason (my wife jokes that she rides a 3-speed even though her bike actually has 16 gear combinations). Of course, this completely defeats the purpose of having a wide-range triple drivetrain in the first place.
The difficulty of keeping track of 27 gear combinations may be one reason for the growing popularity of single speed drivetrains. It may also be a strong argument for internal gear hubs on commuting and city bikes.
Internal gear hubs (or IGHs as they’re often referred to), contain all of the shifting components within the hub. As such, they’re visually clean, they require minimal maintenance, and all of their gears are usable and controlled with only one shifter instead of the usual two found on most modern derailleur drivetrains. Shifting an IGH is linear, straight from the lowest to the highest gear with no possibility for cross chaining and no need to keep track of chain position. This straightforward shifting experience is a real boon to novices, and arguably, it provides a less-distracted riding experience for even more experienced riders.
So what’s it like to shift a modern IGH such as a Shimano Nexus/Alfine 8-speed, or a SRAM iMotion 9-speed? In general, they’re simpler and easier to use than double or triple derailleur drivetrains, with fewer mis-shifts and quieter operation, particularly for novices. Most use either indexed trigger shifters or twist shifters, though we’re starting to see road-style shifters designed specifically for drop bars. Probably their biggest advantage for city riding is that they can be shifted while sitting still. This allows the rider to roll up to a stop light in a high gear, then shift down to a lower gear while waiting for the light to turn. They can also be shifted while coasting and pedaling lightly. It’s not impossible to shift an IGH while under a heavy load, but it’s not advised; doing so is hard on the hub, and you will get some mis-shifts. And again, the linear quality of the shifting experience is simpler and less distracting than keeping track of three chainrings in front and 8-10 cogs in the rear.
I don’t expect to see internal gear hubs replace derailleur drivetrains. They’re heavier, mechanically more complex, and they can be expensive. Derailleur drivetrains are lightweight, highly efficient, relatively inexpensive, user serviceable, and they potentially offer a wider range and larger quantity of gear ratios than are currently available in IGHs. Internal gear hubs, on the other hand, offer simple operation, low maintenance, and a clean, simple look. Each has their advantages and disadvantages in different situations. The key is to fit the drivetrain to the needs of the rider. In my case, while I still enjoy the visual and aural aesthetics of a derailleur drivetrain (there’s nothing like the whirrr of a well-lubed chain snaking through a derailleur), I’m finding internal gear hubs more-and-more appealing as I ride them on a daily basis for commuting and utility use.