11-25 v. 12-25 cassette

Richard Murphy

WOO HOO, just got my Power Tap wheel in the mail.  I have 2 cassettes, 11-25 and 12-25, and was wondering which would be better to install on the new wheel.

Thanks, Richard

Brad Marcus

Richard - Congrats on new powertap. You'll see what you were missing once you start riding with power! There is little difference between the 2 cassettes that you have. You might get a bit more speed on the downhills/flats with the 11-25, but not that noticeable. More importantly, what type of terrain will you be training and racing? Living in Colorado, I'm guessing that you see your fair share of hills. What size chainrings do you have up front: standard or compact. Most advice you'll receive here is that if your riding hills, go with compact rings up front (50-34), and then you can always change the casette based on your needs and/or cycling strength. I ride/race lots of hills and have a compact with a 12-28 casette.

If you search the wiki and forums, you'll fimd lots of really good info from some smarter people than me on this!

Richard Murphy

Hey Brad, thanks for responding.  I have two bikes, a road bike with a 3 ring compact 50/39T/30T and a tri bike with a 2 ring standard 53/39.  

Mike Roberts

Richard, I prefer my 12-25 because i can always find the perfect gear in the middle, whereas there's a gap in the middle of my 11-25 that sometimes makes gearing a choice between 80 rpm or 94 rpm. But if you need to hammer the downhills, gotta go with the 11.

Joe Matchette

Richard - why not start with the 11x25 so you can keep the speed up on the downhills before you spin-out'. If the cadence gaps are acceptable, then go with it. IF not, switch the cassettes and try the 12x25.

Also, have you thought about putting a compact crank on the tri-bike (50-34)?

Dino Sarti

That is very subtle difference. Since they are both 25, you have no climbing advantage with either choice. So, if we look at the bottom end, I like the 11 better than the 12. On gentle downward grade and full downhill assaults you will go faster before "spinning out" with an 11-tooth cog versus a 12.