I was looking at purchasing a new cassette and chain. Looking at the available cassettes for SRAM components, there is a big variety of sizes available:
- 11-23: 11-12-13-14-15-16-17-19-21-23
- 11-25: 11-12-13-14-15-17-19-21-23-25
- 11-26: 11-12-13-14-15-17-19-21-23-26
- 11-28: 11-12-13-14-15-17-19-22-25-28
- 11-32: 11-12-13-15-17-19-22-25-28-32
- 12-25: 12-13-14-15-16-17-19-21-23-25
- 12-26: 12-13-14-15-16-17-19-21-23-26
- 12-27: 12-13-14-15-16-17-19-21-24-27
- 12-28: 12-13-14-15-16-17-19-22-25-28
- 12-32: 12-13-14-15-17-19-22-25-28-32
Now I can understand why someone would choose a cassette based off of how many teeth the big gear has. Some people live in hilly or mountainous areas and desire a higher number of teeth. Some people live in flat areas where they simply won't use those cassettes with a lot of teeth on the big gear.
But why would anyone ever choose to buy a cassette with 12 teeth on the small gear instead of 11? 11 teeth = higher maximum speed. I doubt many people buying a nice set of components (Shimano, SRAM etc) would ever say "I don't need to go faster so 12 teeth is fine with me."
What's the point of 12 teeth when you could opt for 11 instead?