Shimano in general make high quality bicycle components, but unfortunately the main focus of their marketing and design is toward either road or mountain biking. So for bicycle tourists like us some of their parts just miss the mark.
One example is the range of cassettes available. Road cassettes are geared on the higher side with close ratios, and mountain bike cassettes are geared lower with wider ratios. The bicycle tourist needs a bit of both. Close ratios are nice on the flat so that you can fine tune your cadence to ride as efficiently as possible. Very low gears are important to ensure you can winch your loaded bike over big climbs. Very high gears are not so important if we are travelling loaded.
A standard mountain bike setup with a triple crankset and 11-34 cassette will provide ample gear range, but the jumps between gears on that cassette are not very close. This means that on a challenging day where you are facing headwinds, false flats or lethargy it can be hard to get comfortable, and I find myself constantly switching between two ratios that are either side of what would be ideal.
There is a solution. Certain models of Shimano cassette lend themselves to modification. In particular, the Deore series of mountain bike cassettes, codenamed HG61, can be mixed and matched easily as each sprocket is full sized and engages with the splines on the freehub. Most of the sprockets are riveted together, but these rivets are easily removed to separate the cogs, as will be revealed later. Higher spec casseettes such as XT are not suitable because to save weight they feature an inner carrier to which the cut down sprockets are mated.
When I’m touring I don’t really need a high gear at all. Once my speed exceeds 30kmh on a downhill I’m happy to roll and enjoy gravity. So those 11, 12 or even 13 tooth sprockets are useless.
On an ebay whim a while ago I purchased a 12-36 HG61 cassette. I can’t even remember why. To make this cassette useful I decided to purchase another HG61, with 11-34 range and mate the two together to create the touring cassette of my dreams (I know I could have just purchased one from Harris Cyclery, but they don’t ship to Australia). The last and smallest sprocket needs to have an integrated spacer, so I also bought a Shimano 9 speed compatible Miche 14 tooth “first position” sprocket.
So this is my selection of sprockets:
12 – 14 – 16 – 18 – 21 – 24 – 28 – 32 – 36
11 – 13 – 15 – 17 – 20 – 23 – 26 – 30 – 34
and a 14 first position sprocket
This provides many options for customising my selection of gear ratios. For example I can go for very close ratios at the top end and then a few bailout gears for steep hills:
14 – 15 – 16 – 17 – 18 – 20 – 23 – 26 – 32
or another one biased more towards higher gears if you are travelling very light:
12 – 13 – 14 – 15 – 16 – 18 – 21 – 24 – 28
or an all round low geared cassette if you expect constant hill climbing:
14 – 16 – 18 – 20 – 23 – 26 – 28 – 30 – 34
The only real downside to modifying these cassettes is that the Hyperglide ramps that make shifts smoother are placed in staggered positions across the cassette to allow the chain to easily move between sprockets. By replacing sprockets we are going to muck up this arrangement. If you aren’t overly concerned with super smooth shifts this can be tolerated. But there is a workaround.