I believe October might be the best for depending how far north traveling leaves are changing and the experience of cool and cold weather would make trip interesting. Also with Summer over most people are back to school and the daily grind so less are traveling.....Hope you have a great trip Buzzcap7...
right now it's 57% for September. My reasoning is that not knowing if a Southern or Northern route is to be used September will have the overall best weather, little rain, snow, or heat wherever you ride.
September up here can be very rainy and at times we already start to get snow. Two years ago at the Harley Color Rama in Tomahawk it was very cold and snowy.
Southern route - May - everything is blooming and it has not gotten too hot yet
Northern route - Last of August - a lot of the kids are back in school and the show usually has not started in the mountains yet.