Sorry for the threadjack, but I think I could learn something new. I have an old 53/39 105 crankset on my bike with a 9spd 14-25 cassette. I am out of the saddle grinding away on climbs. I have been told that the current rear derailleur won't take more than the 25. Advice on my options for getting the lower gearing that comes with the latest 105 cranksets would be appreciated.