9%

My dad used to love the Tour de France, and he was a really good biker and triathlete. He'd explain to me that the bikers in the Tour de France would bike up hills and mountains with 9% incline sometimes! I understood how steep that was, and the bikers in the race still astound me that they can bike at such steep paces. He also explained to me that the steepest parts of the race was set up in mountain stages and they are the most difficult. There are four categories in the mountain stages and some that are beyond the categories that are 7% or more! Category 4 is shorter and easier than Category 3 climbs that are 5 kilometers and have a grade of 5%. Category 2 climbs are the same length or longer with an 8% grade while Category 1 climbs last 20 kilometers 6 percent grade. Beyond category climbs include an altitude difference of at least 1,000 meters and have an average grade of at least 7%.
We have some 9% inclines here in Albuquerque that are biked frequently such as Tramway to the Sandia Casino. On Saturdays I see people climbing up with their legs pumping, and I see others that coast down the street sometimes going upwards of 35 mph!