My Shimano cassette is the standard HG70 9speed 12-23 with a 53-39 chainring combo.
I ride in the Escarpment region of S Ontario and although I never have to get off and push I'm anerobic at the tops of probably 1/3 of the long step hills. I want to be able to spin a bit quicker. My other (older) roadie has a triple with the 30 tooth Granny....is that ever easy.
Will going up to a 25 tooth make any noticeable difference at all or should i opt for a 27 or 30? The 105 gear train will suck up the chain so I'm not worried about the 27 or 30 being too big.
I don't really need an 11....I hardly ever even use the 12tooth I've got. My average flat speeds are 35 klicks or so and I can do that from a lot of combinations using the smaller middle cogs.
Any experience out there?