Thoughts on Drivetrains

I’ve been fortunate enough to spend time riding at least six different drivetrains over the past year including a reversible single speed/fixed gear hub; a 1×9 with a track crank and 9-speed cassette; a touring triple with an 8-speed cassette; a chain-driven SRAM i-Motion 9 internal gear hub; a chain-driven Shimano Alfine 8 internal gear hub; and, a belt-driven Shimano Alfine 11 internal gear hub.* The following is not intended to be an exhaustive overview of the myriad drivetrains on the market; these are just my thoughts and impressions regarding these particular set-ups.

Track Crank

Single Speed / Fixed Gear Drivetrain
I think the main attraction of single speed and fixed gear drivetrains is that they’re simple and bullet-proof. There’s an appeal to stripping a bike down to its bare essentials, eliminating the need for shifting and fussing with derailleur trim, etc. Eliminating a geared drivetrain is a weight savings as well. The obvious downside to single speed drivetrains is that you’re stuck with only one gain ratio, which may not work for people who live in hilly areas or for those who have physical limitations such as bad knees (which includes many of us over 40 who played sports or rode bikes their entire lives).

1×9 Derailleur Drivetrain
A 1×9 derailleur drivetrain uses a single, track-style crank up front and 9-speed cassette in the rear. I really enjoyed the 1×9 on my old Surly. It was clean and simple, and the linear shifting was similar to the internal gear hubs on my other bikes. Certainly, if a person needs a wider range of gears, a double or triple makes more sense, but for city riding in relatively flat areas, the 1×9 is a good compromise that offers at least some of the advantages of single speed and IGH drivetrains.

Shimano 8-speed Cassette
Touring Triple

Touring Triple Drivetrain
For versatility it’s hard to beat a touring triple drivetrain. A triple provides the widest range of gears while still remaining relatively lightweight and simple to set-up and repair. With three chainrings up front and 7-10 sprockets in the rear, there is great potential for customization within the range of the system. Disadvantages include the need for relatively high maintenance (due to exposure to the elements); a steep learning curve for beginners due to the complexity of overlapping ratios and multiple shifters, etc.; susceptibility to damage in public bike racks; and incompatibility with most chain guards.

Alfine 8
Alfine 8

Shimano Alfine 8-speed IGH
It’s no secret that I very much like the Alfine internal gear hubs. A number of commuting bikes that I tested over the past two years were spec’d with the Alfine 8 including the Breezer Finesse, the Raleigh Alley Way, and a pair of Civias. At this point the Alfine IGH is a mature product with low failure rates and superb performance when used for its intended purpose (commuting). When combined with the Rapid-Fire shifter, shifts are clean, quick, and accurate. One major advantage of this and other high-quality internal gear hubs is that they can be shifted while stopped, coasting, or under power. Disadvantages include a limited gear range when compared to a touring triple; the need for either horizontal dropouts, an eccentric bottom bracket, or a chain tensioner to tension the chain; and added weight when compared to single speed or derailleur drivetrains.

SRAM i-Motion 9-speed IGH
The i-Motion 9 is an internal gear hub from SRAM that competes directly with the Shimano Alfine 8. I’ve enjoyed using this hub on my Civia Loring. Besides the obvious advantage of having one extra gear, the i-Motion also covers a wider range and has more evenly spaced ratios than the Alfine 8. The smaller, more even steps between gears are a real advantage over the Alfine’s somewhat inconsistent spacing. The i-Motion is also easier to remove and re-install in the event of a roadside flat. Disadvantages include shifting performance that is not quite as smooth as the Alfine’s, and a limited selection of shifters, all of which are twist-type.

Alfine 11
Alfine 11 / Gates CenterTrack Belt

Belt-driven Shimano Alfine 11-speed IGH
The only difference between a belt-driven and chain-driven Alfine IGH is the sprocket; the internal parts and shifting performance are identical. The new Alfine 11 IGH is a major step up from the 8-speed in performance (and unfortunately, cost); it’s smoother, quieter, and the gear ratios are more evenly spaced over a wider range. The 11-speed runs in an oil bath which makes it easier to service and should result in longer life and fewer failures when compared to the grease-lubed 8-speed. When combined with Gates’ new CenterTrack belt drive, the result is buttery smooth and nearly silent, almost like riding a well-oiled single speed drivetrain. If you’re already on-board with internal gear hubs, this is the next step that really completes the package. Disadvantages include those mentioned above, as well as the need for a frame specifically designed to allow installation of a one-piece drive belt.

*I’m currently evaluating a NuVinci N360 CVP; I’ll provide a detailed report on that hub at a later date.

© 2011 EcoVelo™