Check the route on Mapmyride.com for elevation changes. Make sure you use a gear ratio that will allow you to handle the steepest hill. Build up your endurance by riding longer rides; 60 miles, 75 miles etc prior to the event. I've done 2 centuries on a geared bike, and would like to try one fixed, but it would have to be less hilly than what I usually ride geared here in KY.