Originally Posted by
Seasonal
well wouldn't 47/15 be okay then? I am running 48/17 right now, but the only two choices i have for the chainring i am getting is 47 or 49
No.
Increasing the number of teeth on the front has the opposite effect of increasing the number on the rear.
If you like your current gearing, changing one tooth on the front makes a very small difference. Changing the rear by one tooth makes a greater difference. You wont be able to achieve the exact same gearing if you change the front by only one, because any change to the rear (in an attempt to compensate) will go beyond.