Our trip has a variety of terrain: mostly flat in the Netherlands and along the Rhine in Germany, mountainous in Switzerland, and a mixture of both in Italy.  That means having enough low gears to climb those mountains is necessary, but having too many of them means lugging extra weight up those mountains! Gearing for a regular road bike would usually be something like two chainrings (the gears) on the front (#5), one with 53 teeth and the other with 39, and a cassette (the cluster of gears on the back wheel, #3) with a range of gears like 11-25 or 12-27 teeth. Austin lies at the edge of the Texas hill country, and a 12-27 cassette is perfectly fine for everyday riding, but there are some nastily steep climbs where it can be a real struggle.  Thankfully, those steep climbs are all short enough that I can power through them in a minute or two.  But if they were more numerous, or even worse - longer! - then I would be in real trouble with those gears. Touring bikes, just like mountain bikes, usually have what is called a triple crank arm (crank arm - #4), which simply means there are three chainrings up front by the pedals.  That allows you to have a very low "granny" gear for those extra steep climbs. Like so many things with bikes, the choice to use a triple crank arm is both easy and hard. To get that granny gear, a new set of cranks is required (cranks are what the pedals are attached to), and because the gears are shifted through the brake handles, a new set of brake handles would also be needed.  So, instead, I chose to get a cassette with a larger range of gears for the back AND I also chose to use the smallest possible inner chainring up front, which for my bike would be a front pairing of 52/36 (a 16 tooth difference is the max).  Oh, and I also need a new rear derailleur (#2) to accommodate that larger cassette. And maybe a new chain if my current one is the wrong length! After buying all the new pieces and tearing everything apart, I learned that I cannot put a 36 tooth inner chainring on my current cranks!  Because of the way the chainrings are made, the bolts holding the chainrings to the cranks have a larger spacing between them for situations where larger chainrings will be used, e.g. a 53/39 pairing.  Smaller chainring pairings have a smaller bolt pattern and thus need different cranks. Consequently, that means I needed new cranks after all!!! The good news is that SRAM makes a crank set with a 50/34 pairing (2 fewer teeth up front than I originally wanted - a real benefit), and as a bonus, I was able to order my new cranks in a 175 mm length instead of the 172.5 length I currently have on this bike (my regular road bike has 175 mm cranks). All of these little differences add up - losing a couple teeth on the inner chainring, additional teeth on the cassette, slightly longer crank arms - and mean that this bike will now give me the equivalent of 3 more lower gears than I am accustomed to having on my rides around the Austin hill country.  Now, even with the additional weight of the panniers, and even if some of the climbs are a bigger bitch than expected, I'll have a few bailout gears just in case.

2 Responses to Gearing

  1. Pingback: Gearing | SBR Blog

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