When I was riding 48/16 I could keep up with a 20-25 mph paceline. It was harder on the SS, but not much harder. If the group got up around 27 or 28mph it got a little tough - I'd fall to the back of the pack and pedal like hell. With my new 46/16 commuter, I can keep up with a 20 to 22 mph ride OK. I think 25 might be a little "spinny" for me though.

Hope that helps.