I recently purchased a Trek 7700 hybrid. I’m a little older than I was when I purchased my last road bike, by about 25 years
, and I haven't ridden very much in the last decade. I had several objectives for this purchase including wider tires more appropriate for some of the sand and dirt that I occasionally encounter, a softer ride, and better choices of gearing than my old 10-speed provided, especially in the “middle” range between 50 and 70 gear inches.
I didn’t particularly like the factory choice of gears. The 26-36-48 chainrings combined with the 11-32 cassette resulted in a lowest gear of about 22 gear inches and a highest gear of about 118 gear inches, a very wide range IMHO. For comparison, the range on my old bike was about 33 to 100 gear inches and I rarely, if ever, used these extremes. Also, there were three ratios using the 36 tooth chainring that were essentially duplicated with the 48. Thus, discarding the cross chained combinations and duplicates, this 27-speed bike became an 18-speed with about 5 of those too low or high to be useful very often, if at all.
I considered changing the chain rings, replacing the 26 and 36 with something larger but this didn’t seem economically practical, and it would still leave the steps on the rear with the same percentage changes, thus not very suitable for subtle changes.
I figured that building a cassette from scratch probably wasn’t cost effective, so I looked at stock cassettes. I built an Excel spreadsheet and played with some numbers. I found that replacing the 11-32 cassette with an “off-the-shelf” 13-23 (that’s 1 tooth steps from 13 to 19, plus 21 and 23) made a very good combination. The resultant range goes from about 31 to 100 gear inches. More importantly, it provides smaller steps between adjacent gears making it much easier to find a gear that fits both the terrain and how I’m feeling at any particular time.
I could have purchased this bike at a number of LBSs for the same price. The clincher for my selection was that only one shop, Freewheel Bike in Minneapolis, was willing to exchange the original 11-32 cassette for a comparable quality 13-23 and shorten the chain (2 links, I think) for no additional charge. Everything else in the drivetrain is stock. BTW Freewheel has other reasons to recommend it. As a friend of mine said about the people who work there: "They ride bikes!"
Here’s a chart showing the resultant gearings; chain rings are listed across the top, cassette sprockets are listed down the left:
Code:
26 36 48
23 30.7 42.5 56.7
21 33.6 46.6 62.1
19 37.2 51.5 68.6
18 39.2 54.3 72.4
17 41.6 57.5 76.7
16 44.1 61.1 81.5
15 47.1 65.2 86.9
14 50.4 69.8 93.1
13 54.3 75.2 100.3
I haven’t found the time to do as much riding as I’d like. However, on a few rides, from about 15 to 30 miles each, I’ve found that I like this combination.
I hope this information gives others some ideas what they might do to make their bikes "fit" them, and their needs, a little better.
Mel