Rear wheel was worn so paid too much money for a new wheel including labour at my LBS. New wheel was a bottom end of the market Shimano wheel (about 70 quid), but still supposedly better than the old alex rims wheel. Since then, it has felt much harder work cycling. My average has gone down and I'm getting more out of breath. On my eight mile commute I used to hardly sweat, but now I'm needing a change of clothes after I get home. I've put the bike on the stand and the wheel runs fine and doesn't stop for a while if you give the pedals a good turn. The rear brakes aren't rubbing nor do they get stuck on. I don't know what's going on and it's doing my head in. Part of me thinks it could be in my head, but cycling definitely feels a lot harder so I reckon something's not right. Suggestions? Ta muchly.