Internal gear Hubs and Belt Drives for Commuting and Touring

Since I just finished my Pan-American bike tour (http://www.panamericantour.net) I won't be doing any big tours for a while, but I plan to commute to my new job by bike and I've been thinking about the perfect bike for the job. As always, I had a few things at the top of my priority list: steel frame, internal gear hub, belt drive and disc brakes - a list similar to that of my dream off-road touring bike.

I've always thought that internal gear hubs are a great idea, and they seem like the logical evolution of bicycle transmissions. The most highly regarded internal gear hub is the Rohloff Speedhub, and Shimano recently released the Alfine 11, so those are the two that I looked at and will be writing about. Internal gear hubs are protected from the elements, requiring less maintenance, and have other benefits including the ability to shift without pedaling.

One of the greatest parts of an internal gear hub is that it allows you to use a belt instead of a chain. Gates' Carbon Drive system is the big player in that market. A belt lets you avoid the rust, black calves, and maintenance that plague the riders of chain-driven bicycles, and can also give you some weight savings to boot. The tricky thing about using a belt instead of a chain is that belts are continuous loops, so while you have to open a chain to get it around your frame, you need a special frame that opens to accommodate the belt. At this time there aren't many framesets designed for internal gear hubs and belts.

Unfortunately, I did my research out of order - spending time searching for off-the-shelf belt driven bikes (see Gates' Contact page, and the Belt Bikes website), as well as framesets, before crunching the numbers to see what gear ratios a belt bike could give me. Lets start with what Gates gives us to work with. Their CDC and CDX lines only allow you to use a 24 tooth sprocket on back with an Alfine hub, and following Shimano's recommendation of using a gear ratio of no less than 1.9, that leaves you with a minimum front sprocket size of 46 teeth. If your comfortable cadence is 90 RPM and you have 700c wheels, you get the following speeds (in MPH ) from this combination:

7.43
9.60
10.85
12.37
14.02
15.98
18.21
20.61
23.49
26.61
30.34

Seven and a half to thirty miles per hour?!?! This is totally ridiculous for a touring bike, and almost as impractical for a commuter. Incidentally, the Alfine 8 has very similar gear ratios for speeds one to eight as the Alfine 11, so if you don't plan on riding between 20 and 30 miles per hour, you can save yourself about $300 USD by purchasing that hub instead.

Now lets look at the Rohloff Speedhub. Rolhoff requires a ratio of right around 2.4, which you can get pretty close to with a 38/16 sprocket combo - at a ratio of 2.38 it is the lowest they permit. Again, at 90RPM with 700c wheels, you get the following speeds in MPH:

4.87
5.52
6.29
7.14
8.10
9.22
10.48
11.91
13.52
15.39
17.46
19.82
22.56
25.62

So right away we see a much saner low-end speed, which is good if you plan to spend any time in the hills carrying gear. Also, the high-end speed is more reasonable for a touring/commuting bike.

With a standard 10 speed cassette Shimano groupo, you can get a low-end speed of 4.63mph with 24/36, so the Rohloff is more in line with this.

After seeing those numbers, I decided that if I were to build a bike strictly for commuting, I would go with the Alfine 8, but it's hard to justify the price for a single-purpose bike. For touring I would need a Rohloff, but using a Rohloff equipped bike for commuting and around town just seems a little crazy.

In the end, I decided that neither combination suits me well at this time, and I'll have to continue to make due with one of those old-fashioned, chain driven bikes. Wish me luck!