FS = Fast and Smooth
FT = Fast but Technical, with a few obstacles
MX = MiXed; speedy but blunted by intermittent obstacles (turns, traffic, etc.)
HT = Highly Technical and potentially hazardous due to road and/or traffic conditions
#1: Onion Valley Road, California
TOTAL ELEVATION LOSS: 5,169 feet
LENGTH: 12.5 miles
AVERAGE GRADE: 7.8%
Onion Valley is steeper and longer than the Tourmalet, with the same hair-raising exposure as the famed climb regularly included in the Tour de France. You also get sweeping views of the Sierra Nevadas and Kings Canyon National Park, making this the best overall descent for its combination of scenery and riding. Once you start rolling from the parking area in a high-alpine bowl, you'll encounter a fast segment that ends with an S-curve. The route then descends through long and graceful but exposed switchbacks, after which you'll quickly gain velocity again. A final section of steep switchbacks scrubs some speed one more time. But the last stretch is straight and the exposure is behind you, so you can relax, kick into high gear and finish with the kind of smile that comes from one of the nation's most sublime downhill experiences.
#2: Haleakala, Haleakala National Park, Hawaii
TOTAL ELEVATION LOSS: 9,997 feet
LENGTH: 36.5 miles
AVERAGE GRADE: 5.2%
This monster volcano on the island of Maui is so popular and so long—a whopping 36.5 miles—that outfitters offer guided downhill-only bike tours. There are several stages to the nearly 10,000-foot total descent. Heading down the paved trail at the peak to the initial section of road gives you expansive Pacific views over a moderate grade; near the middle the route becomes a bit more technical as it switchbacks downward; and near the end it straightens for screaming-fast speed. Haleakala can wear you out going up or down, so come prepared for both the epic distances and fast-changing weather; summer temps can drop abruptly into the 40s, with gale-force winds.
DIRECTIONS: On Maui, head to the town of Paia and follow signs for the national park. (ups.gov/hale
#3: Little Cottonwood Canyon, Utah
TOTAL ELEVATION LOSS: 3,365 feet
LENGTH: 8.8 miles
AVERAGE GRADE: 7.2%
Little Cottonwood, situated in the Wasatch Mountains southeast of Salt Lake City, is a steep-walled canyon just above the Alta ski resort, and the ride down through it is like snowboarding one of the area's best-designed intermediate trails: It's smooth, flowy and more fun than almost anything else you can legally do. The hill starts with a steady, steep grade, so you'll pile on speed quickly. But mostly, the road snakes down with gentle curves, and once you find your line you can settle in for the long descent. There is no exposure here; instead, the soaring canyon walls seem to funnel you down the hill. This one ends much too soon.
DIRECTIONS: From Sandy, head east on Route 209 to its junction with Route 210 at the mouth of Little Cottonwood Canyon; from there, head east on 210.
Postcards From the Pyrenees: A look back at the Tour's dramatic mountain stages