On some of my longer metric century cycle rides, I encounter 20% gradient ascents which I'm failing to conquer. They tend to be long narrow lanes, loose gravel in the centre or greasy under trees and getting out of the saddle looses traction. My regular 50km loops only encounter up to 15% gradients which I can just about haul myself up. My bike has a Campy Veloce compact chainset and a 29t cassette, enough for most hills but obviously not all. My first thought was to buy a 32t cassette but Campy don't make them. What are my options? I've considered changing the groupset to Shimano 105 with the 32t cassette. Would that make much of a difference or would I be wasting my money. Any advise would be appreciated.