Single speed drivetrains have significant appeal. They’re simple, lightweight, and tough. They boil the riding experience down to its most basic form, eliminating the distractions associated with more complex drivetrains while putting the rider more closely in touch with the terrain. The trade off for this simplicity is the inability to change gear ratios (of course) which makes riding in varied terrain more challenging, particularly if any kind of loads are involved. Plus, riding a high gear at low cadence can put considerable strain on joints and connective tissue which can lead to injury over the long term.
At the other extreme are 3×9 27-speed drivetrains designed for mountain biking or loaded touring. These drivetrains are well-suited for riding in rugged, off-road conditions or carrying heavy loads long distances over mountain passes and across deserts. In other words, they provide a wide range of gears to suit those who ride in a wide variety of conditions. They’re so effective that they’ve become standard issue on many bikes, even bikes that may never see a single track or a mountain summit. The downside to these versatile drivetrains is the added complexity and cost, as well as the higher maintenance required to keep them running efficiently.
After riding a number of 8-speed and 9-speed IGH-equipped bikes for the past two years, I’ve found they cover my needs for city riding quite well as long as the overall range is sufficiently low. And on my bikes with double and triple cranks, I’ve found I spend nearly 100% of the time on a chainring in the 40-42 tooth range. This has me thinking that a 1×9 drivetrain with a single 42 tooth ring up front and a 11-34 cassette in the rear may be a perfect set-up for the type of utility riding that I do on a daily basis.
Consider the following:
- The gear combos I use 99% of the time on my derailleur bike: 42 x 11/34 (700c)
- The gear inches for that range: 33.4″ – 103.1″
- The gear/cadence/speed relationship in the highest gear: 42×11 @ 80 rpm = 24.5 mph
- The gear/cadence/speed relationship in the lowest gear: 42×34 @ 60 rpm = 6 mph
On a city bike to be used for commuting or running errands, I rarely top 20 mph, and I certainly have no need to spin out past 80 rpm at 25 mph, even on a downhill; beyond that I just coast.
On the low end, I find 33” (6 mph at 60 rpm) plenty low for loads up to 60-70 lbs on moderate hills, the typical max I experience. Of course, on a cargo bike in mountainous terrain, where the loads are greater and the hills are longer and steeper, lower gears are a must.
I’d say that I’m going to give a 1×9 drivetrain a try, but the fact is, I’ve effectively been using a 1×9 drivetrain for a number of years. You only have to look at my crank to see what I mean; the outer ring was replaced with a chainguard long ago, and the inner ring has zero wear on it. I do plan on replacing the triple with a single crank, if for no other reason than to make it official.
All calculations were made using the late Sheldon Brown’s excellent Gear Calculator.