They take their mountain biking seriously at Christini Technologies Inc., Philadelphia. So seriously, in fact, they have designed and built an all-wheel-drive bicycle. The bike has a fairly conventional six-speed system that uses three hub-mounted gears and two on the main sprocket. A handlebar-mounted switch engages an on-the-fly clutch. It puts the rear spiral gear in contact with the hub gear and transfers power using shafts that travel inside the tubular frame to the front fork. The head-tube gear, located in the gooseneck, then transfers power to a front spiral gear set to drive the front wheel. A slight gearing differential sends power only to the rear wheel while the bike travels over level ground. But the moment the rear wheel slips, power goes to the front wheel. Power also goes to the front wheel when it decelerates, as when it hits a rock or starts to wash out in a corner. According to Christini, the AWD system increases control, stability, and traction on slippery and loose surfaces.

The bike, which sells for $1,500 to $2,500 depending on the suspension package, uses stainless-steel gears, and an aluminum frame and driveshafts. The front fork features a telescoping sleeve to accommodate fork travel and cushion the ride, while disc brakes front and back provide stopping power.