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:
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

You must be an engineer.
Welcome to the forums.

You may find that 23 tooth a little small when you start climbing hills with legs that are 10 years older. If you are lucky enough to have no hills, there probably won't be a problem.

Just a suggestion here, technical observations, such as yours, are usually posted in the Mechanics Forum and may, or may not be moved by the moderators to that section. It will still be listed on the "New Posts' and be seen by most members.

For sand and dirt, you may find that you need the lower gears. Before you change them, give them a spin. You cant select your gears in isolation from the terrain or tyre type.

I run an 11-28 8 speed with 44-38-28. This gives a practica; great range of gears for commuting/touring with low enough gears for most Scottish hills.

I don't think it's ever useful to try to use gear charts as often there is too much double changing and duplication. I look at mine as 3 sets of 4 choices , outer 4 rear with the 44, middle 4 with the 38 and inner 4 with 28.

I spin out of the tp one at 30plus which is fast enough, but or most touring etc I have a good spread with good chainline.

With the chart you've given us remember that chainline prevents you from using extremes.

MichaelW and chewa,

The combination that I've got now goes a little lower than that of my old bike (30" vs. 33") and the high end is the same (100"). I think that this is quite suitable for the riding I do. In the limited riding that I've do with this combination I find that I like it alot.

My lowest gear isn't quite as low a chewa's, by about 10%. Likewise, my highest gear isn't quite as high, by about 8%. I'm not convinced that these are very significant differences.

Your considering your 24-speed as three sets of 4 is quite useful, although maybe a little conservative. I might think of it as 3 sets of 6. On a 9-speed cassette this is 3 sets of something between 6 and 8. I suspect that the number of truly usable combinations is very dependant upon the particular cassette, chain, rear derailleur, and maybe chainring combination. Please note that the cross-chained combinations are in the mid ranges, not the extremes relative to gear ratios.

I didn't start this thread with the intention of saying, or even implying, that my choice is what everyone, or even anyone, else should do. I simply wanted to show others how a relatively simple change to what the manufacturer selected may make a significant change in the rideability of a bike.

To each his own,
Mel