For a solo training or fun rides it takes me about 4 to 5 miles of easy spinning and progressively faster riding to warm up. Somedays it takes less and other days more warm up time depending on how the last ride left me. On group rides it does not matter how long I warm up since I'm part of the group, but I do make sure to spin at a higher cadence until the group ramps it up. If I get to the start location early I'll noodle around the parking area before the ride begins. My warm up for races is to get in 10 minutes of easy spinning followed by x 3 pickups taking my heart to the bottom of zone 4 (138 bpm) for 2 minutes on the first pickup, then to the bottom of zone 5 (154 bpm) for 30 seconds on the next 2 pickups, then 5 to 10 minutes of easy riding. I try to get the warmup done no more than 15 minutes before the start of the race. I raced last Saturday and the pace picked up to race speed as soon as we passed the start line from a "netural start". I'm glad I did a full warmup before the race start. Our average speed for the 24 mile race was 24.1 mph and my HR was so high that I turned my HR monitor over so I could not see it! I think I was in zone 5 HR for almost the entire race. If I hadn't got to the higher HR in the warm up I probably would have blown up on the first excelleration. My buddy didn't do the last two pickups with me and he was "off the back" before the end of the first lap.