Since the rather more chilly weather has struck, my times on my daily whizz are getting significantly slower, and I'm either getting less fit as I cycle more, or there's some other cunning explanation (which of course I'm secretly hoping for as it would be a shame otherwise ). A few weeks ago my average speed was 27.5km/h, pretty consistently. Then I changed tyres and it fell to around 25 (so I changed tyres back again ), but the inexorable decline continues. Today I barely got over 24. Either I have some nasty illness that makes you feel great but cycle like a snail, or there's some other explanation… could it be the cold? I'm still in my shorts, although layer the top half appropriately, and I have to say my legs don't feel cold. Clutching at straws. Someone make me feel better Edit: A new conspiracy theory… the US government have tweaked the GPS satellites to make everyone run faster?