I have a bike with a double 53/39 on the front and a 8 speed 25/12 cassette. I am 50 years old and ride about 100 - 120 miles a week. I am pretty happy with the gear selections except when I hit a real steep hill... I can ride up of them but I can not keep up any cadence and even have to resort to standing sometimes.
I am looking for opinions on if changing the cassette to a 27/13 or a 28/13 will it make much difference and can I do this without replaceing the derailer? It seems to me to be the most inexpensive modification to get a lower ratio.
a 39/25 combo results in a 1.56
a 39/27 combo results in a 1.44
is that the correct way to express the ratios?