Originally Posted by
wolfchild
Dressing warm will only keep you warm, prevent hypothermia and prevent frostbite, it isn't going to make you go faster or make your ride more efficient...I don't know the science behind it but anybody including myself who has ridden in real cold knows that extreme cold does slow you down. Breathing in minus 20 Celsius is also a lot harder then breathing in plus 20 Celsius.
You shouldn't be comparing -20C with 20C. You should be comparing with 40C.
-20C is cold but manageable with the right kit. 40C is crippling no matter what you try to do.