Simple physics dictate that in order to descend, one first must ascend. When it comes to cycling, it's widely known that climbing is not for everyone, although many believe that there is no greater descent than a descent earned. For those who fall into the former category and just go for the downhill bomb, Gnar Gnar Tours is your rescue, providing regular shuttle service up South Mountain every Wednesday, Friday, and Saturday. So, if you're one of those huckers bounding down National or Geronimo Trails on one of those burly downhiller rigs, a tow to the top with Gnar Gnar may be just what the doctor ordered. Runs up South Mountain cost $5 a trip or $20 for the day, and the shuttle stops at Scorpion Gulch near the park's main gate, the Heard Scout Camp, and Cactus Bikes in Akwatukee. There's also a shuttle service to Black Canyon Trail and up north to Sunrise Ski Resort, for a total heat escape. Bike rentals also are available for those who want to indulge in the torment of South Mountain but are in need of wheels.