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Tuesday, January 12, 2016

New thoughts on gearing

For years, I resisted switching from 8-speeds to 9-speeds. I wasn't willing to upgrade until 9-speeds had become reliable (early 9-speed chains were nasty: Lisa and I not only broke a chain on a shift, but tore off pieces of the aluminum chain ring as well). With the arrival of the triplet, however, I was forced to switch to 10-speeds. Not that more speeds ever did much for me as a tourist: unlike a racer, I didn't need little jumps between gears, and friction shifting was more than adeqaute for me, even on 9-speed drive-trains.

Having recently gotten back into mountain biking, however, I'm seeing that I should have kept track of drive train evolution in the mountain bike business rather than looking at road offerings. Unlike road bikes (and like tandems and touring cyclists), mountain bikes frequently shift under load, have to put up with dirty conditions, and need strong wheels, so evolution there has direct applicability to those of us who don't race. Even better, mountain bikers regularly climb super steep stuff, and so need very low gears that only tourists tend to use.

The most significant change in the mountain bike drive train has been the introduction of 2x10 or 2x11 gearing. What's happened there is that with the introduction of wide range (11-36 or 10-42) cassettes, mountain bikes no longer need triple chain rings in order to have a good range of gears. Going from a triple to a double is huge! Your front derailleur no longer has to do as much work, you no longer risk chain suck (I've torn off more than one front derailleur due to chain suck).

The typical mountain bike would use a 22x34 or 24x38 front chain ring coupled with a 11-36 rear cassette. (10-42 cassettes exceed $100, and are typically paired with a single 30t chain ring). This grants you a lower gear than the traditional 24x34 touring drive train, while granting a 93 inch high gear, which is more than adequate when touring. Not only does losing the 3rd chain ring reduce shifting headaches, you also lose weight on the bike. You also gain the ability to use double chain ring indexed shifting (via STI, for instance) if you are so inclined. The double chain ring STI setups are much more reliable than the triple setups, and also don't have issues with trimming. The only downside I can think of is durability: smaller chain rings will wear faster. In practice, replacing chain rings every 3 years instead of every 5 is no big deal.

The 1x11 drive train, by contrast only grants a middling lower gear and has only an 81 inch high gear, which isn't adequate for touring. In fact, even for just mountain biking it probably isn't practical either, unless you're very strong or it's combined with a very light bike. I tried it during my Santa Cruz factory demo, and it was barely usable then, but it wouldn't be sufficient for any of the seriously painful climbs that I'd want to ride without making my knees hurt.

In short, if your existing touring bike drive train works, there's no need to switch, but when building a new touring bike or replacing a drive train, the new mountain bike drive trains are a much better fit than the road components traditionally used on touring bikes. As 10-42 cassettes drop in price, the new double chain ring mountain bike setups offer the same wide range gearing as the older triple setups, with lower weight and more reliability. There's no reason to ever consider a triple chain ring setup for road touring again.

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