Will I need to make adjustments to the derailer when changing my road bike cassette to a larger one?

Question

On a road bike with a compact crank (double chain ring) I am changing the cassette from an 11-23 to a 12-27. Will I need to make adjustments to the rear detailer to insure proper shifting? Will this change help me climb or will I still be embarrassed and left behind by my girlfriend.

Answer 1

First, make sure that your derailleur will handle the 27t large cog.....some of them max out at 25t or 26t.    

Other than that, the only thing you'll need to do is adjust the B-s***w on the rear of the derailleur, and perhaps make some very fine adjustments to the limit screws.   Most of the time, you won't need to touch the limit screws, but it's always best to start from scratch and set up the derailleur as if it's brand new.   Also, you may want to add a couple links of chain, or just use a new one and cut it to the proper length.  

If you need any help with all of this, a shop will do it reasonably cheaply, or you can visit the "repair help" section at http://www.parktool.com for great instructions and photos on how to do everything correctly.  

If your girlfriend really kicks ***, you might still get embarrassed, but by changing to the new cassette you'll be gaining 2 extra low gears.   If that helps your legs feel fresh after the climbs, then maybe you can keep up with her.  LOL   :o)

Good luck!   :o)

Answer 2

I just did pretty much the same thing on my Shimano setup. SWEET!!!

Especially makes a difference on longer steeper rides.  Everyone has some limit for their number of high effort standing climbs.  With the 34/27 there are few that I have to stand and strain.  That doesn't mean that stronger riders won't still be faster...