What cog is replaced with the 11-23 cassette?

10 speed? The 18. Good gear, that one. Good flatlander gear in the big ring at 40kmh.

Nine speed: The 16. Another good one in the little ring.

For you, I would suggest the 12-23. You won't miss the 11.

You get "straight through" cogs 12 to 19, including the sweet 18, then 21 23 to get you over the climbs.

Personally 11 is over kill. I never got dropped for not having a big enough top gear, but the tough hills & rises where you are searching for that right ratio are far more critical.

Enjoy

I feel I'm okay at sprinting and I often get to around 35 mph in the finishline sprint but rarely work my way down to the 12 tooth gear in the sprint. There is one race each year with a long downhill finish where I came close to spinning out the 12 tooth, I hit 45 MPH during the sprint on that race. The pros were running 11 tooth gears for that race and were hitting 55+ Mph at the finishline.

I know I have gotten in arguments with the TimeTrial folks over this one. Some say they use the 11 tooth in TT to keep the speeds up in the mid to upper 20's in a TT while running a moderate cadence. I would not know about this because I suk at TT and find I need to run a high cadence to run those kind of speeds.

You get "straight through" cogs 12 to 19, including the sweet 18, then 21 23 to get you over the climbs.

Personally 11 is over kill. I never got dropped for not having a big enough top gear, but the tough hills & rises where you are searching for that right ratio are far more critical.

Enjoy

12-23 in 9sp works well for me as i'm 90% in the 21, 19,18,17,16. When i go to 10 sp i'll go with 12-23 or 12-25.

I was thinking about a 12-27, but after a few rides with 12-23 cassette, I don't really think I need it. I seem to climb ok with the setup I have.

Skip the 11. I'd much rather have a 16t or 18t. I used an 11 about once and realized it was a waste for ME personally. In my bike club, that is also the general consensus. We all ride 12-23 thru 12-27, with some starting at 13t or 14t for very hilly areas. 11t seems mostly for racing with long flats and big downhills, IMHO. But with dowhills there come UPHILLS, and the 11t won't help much there.

I have an Excel spreadsheet that evaluates/compares the different cog combos. If you want it, email me at surveyor12 @ comcast . net and I'll send it to you for free. It graphs charts and has a host of features you may find useful in selecting cassettes. Everyone who has received it has enjoyed using it. (Geez, maybe I should start SELLING it??? Nah...)

I feel I'm okay at sprinting and I often get to around 35 mph in the finishline sprint but rarely work my way down to the 12 tooth gear in the sprint. There is one race each year with a long downhill finish where I came close to spinning out the 12 tooth, I hit 45 MPH during the sprint on that race. The pros were running 11 tooth gears for that race and were hitting 55+ Mph at the finishline.

I know I have gotten in arguments with the TimeTrial folks over this one. Some say they use the 11 tooth in TT to keep the speeds up in the mid to upper 20's in a TT while running a moderate cadence. I would not know about this because I suk at TT and find I need to run a high cadence to run those kind of speeds.

I agree with those TT folks. For me personally, on a rolling course the 11t is great for bombing downhill and then hammering for awhile (at something like 65-75rpms). Not that I get spun out in the 12t, but I'm out of my comfort zone of cadence in that situation. TTs are all about picking up speed especially where others miss it, so I find that the 11t lets me go faster, more comfortably. For a road race/crit however I agree that the 11t is overkill.