hillcrawler

Hello, i've another newbie question for you if you don't mind answering.

I've a compact cranckset (50x34) and a 9sp casette with 12-23T ratio. So, how many combinations do i have here? Both on small and large cranck?

nhluhr

9 speed cassette... times two chainrings... 9 x 2.... do the math man.

valygrl

multiply the number of chainrings (front) by the number of cogs (rear). 2x9=18.

The important thing is not how many, but what range. Your cassette's 23 tooth low gear is not very low, and the 12 is not very high. If you live somewhere with a lot of long or steep hills, you might want a different cassette. (esp. with a name like 'hillcrawler' ) If you live somewhere pretty flat you are good.

Cassettes can be inexpensive and are very easy to change.

fstshrk

You must have an older tiagra. They went 10 speed last year with it.

idc

4500 = 9 speed
4600 = 10 speed

I got a bike with 9 speed Tiagra this year and love it.

Anyway, the number of combinations is not that meaningful, since you won't want to cross chain so you won't really be using 18 combinations. Probably more like 12-14.

Velo Dog

You can calculate the ratios and learn how many USABLE gears you have. It's common for there to be duplicate or near-duplicate ratios, so the small chainring and one cog in the back gives nearly the same gearing as the big ring and a larger cog in back. It's not particularly useful information for everyday riding, but if you start swapping cassettes, you can figure out what you need.
Don't worry about having a nine-speed instead of a 10. It's meaningless in recreational riding.

Suburban Grind

Look at it graphically:

https://www.gear-calculator.com/#KB=3...0&UF=2111&SL=2

Looks like 7 useable gears on each chain ring - after eliminating the two combinations on each that are cross-chaining - with no overlap. So 14 total useable gears.

But like the others said, the biggest sprocket on your cassette will make for some tough climbing even though you have the 34 tooth compact bailout chain ring.

I wouldn't worry about the 50 x 12 downhill combo - should be good for 35 - 40 mph if you're willing to spool up your cadence to 110 - 120 rpm. That's scary enough for most.

hillcrawler

Maybe the high gear cogs (12.13.14.15.16.17) is meant for the large chainring and lowers ones (19.21.23) are for the smaller. Would it be too narrow configuration?