You will reach your target rate at lower efforts and speeds at altitude than at lower elevations. Make sure to take on fluids and food at the rest stops. Do not allow yourself to become dehydrated. Carry extra clothing. Once the afternoon hours roll around, weather can change quickly.
Wind can dramatically reduce temperatures, and hypothermia can set in rapidly.
If you need to walk the steeper sections of passes do so without feeling guilty, even the best riders in the tour will have to stop to catch their breath at the top of the passes. With a better understanding of your responses to altitude and a well thought out training program, you can have a very enjoyable experience Riding The Rockies. Edmund R. Burke, Ph.D. is a Professor at the University of Colorado at Colorado Springs and writes regularly on health and fitness for Bicycling Magazine and Velonews.