Originally Posted by poeli
May I ask you how the gp5000 tl improved your commuting times? Or not much a difference?
My commute is about 15km shorter than yours, and about 150m elevation climbs. It's all paved road but no bike paths. When I switched to 32mm GP5000 S TR (not the TL), the marginal gains were in the long straights and climbs (rolling resistance), and down hill corners (grip). In the city traffic, there is literally no gains. Equipment efficiency gains from tires/wheels will be at best very marginal, depending on your route. I gained about 10W on the flats. The biggest gains will be gearing optimized for your ride, which is why I asked about your drive train. No matter what, you won't be cutting off 20 minutes off your commute with just equipment change.
Switching from a pannier to a backpack, will lower your Cda. However, depending on how heavy it is, the toll on your body, in terms of heat etc may make that aero gain moot. I know I don't like a backpack for a long ride, especially in summer heat and if it's a heavy bag.