Contemplating buying a bike online. It'll ship with a full 105 drive train, including a 11-25T cassette. Seeing that I suck on the climbs I'm thinking of swapping out the 11-25 cassette for a Tiagra 12-30 (both 10 speed). Will I need to get a new chain as well? My intuition says yes because I'll need more links for the bigger sprockets.