A few years ago, I climbed the west side of California’s Monitor Pass as an out-and-back. The 5.5-mile, 2,600-foot climb tops out at 8,300 feet and is a great hammer session, but I found the descent—smooth, fast, and curvy but not technical—to be pure bliss. What made Monitor feel, to me, like magic? It might come down to gradient and curve, says Ingmar Jungnickel, aerodynamics R&D lead at Specialized.
How Gradient Translates to Speed
Jungnickel graphed out terminal velocity (the speed a rider would travel in a straight line, no pedaling or braking) for a 165-pound rider at downhill gradients from 2 to 12 percent. This rider will reach about 40 mph on an 8 percent grade. Because of wind resistance, an increase in gradient does not lead to a 1:1 increase in speed. Monitor Pass is about 9 percent, and I weigh 143 pounds, so I maxed out at around 40 mph, in the “fun zone” for me. Your comfort level might be different.
The Ideal Curve
Jungnickel also tracked the minimum turn radius a rider would need to navigate a curve without braking, at varying speeds (shown here from 25 to 40 mph). The tighter the turn, the slower you have to go. At 40 mph, in dry weather, a turn must be no tighter than a 196-foot radius for an average rider to get through it without braking. The corners on Monitor were mostly wide sweepers, so even at 40 mph I could link them and carry my speed.
