my coldest ride ( I don't consider it a ride unless your out for 100 miles or more) is -15°F, with proper gear & equipment, now problems
tried going out at -25 once, but couldn't get the bike started till it warmed up to -10
gear
thin silk longjohns & longsleeve T
military surplus thermal longjohns
gerbings jacket liner
firstgear HT pants & jacket w liner
windstopper balaclava
Sorel 1964 boots w -100 white felts instead of blue -40 normal felts
Snowmobile helmet w double pane visor
Gerbings gloves
HotGrips
Duct Tape around waist to seal jacket to pants
Pirelli MTR60-Corsa tires (knobs actually allow tires to get warm, you see steam rolling off them when you pull over to a snow covered shoulder)
yup, got a lot of strange looks
2½ hours later when I got back home from my approx 100 mile ride, I was sweating my butt off
Cold Air = Free Horsepower, so much so that a quick roll on even in 3rd gear might loft the front wheel a bit, throttle response is unbeleivable at that temp;D