Only the bravest travelers are interested in biking through Kathmandu's heavy traffic, but once out of the city center, mountain biking is awesome! You can tool around the back roads of the Kathmandu Valley on short rides or get off-road for day rides or longer adventures.
You are welcome to bring your bike, but outfitters here have good bikes for you, withhelmets and safety gear. A guide goes with you for off-road trips and, as you like, for short rides. A sag wagon follows along or is on call. There are many nice routes near Kathmandu and Pokhara.
Longer trips go around the Kathmandu Valley rim, to the Langtang region north of Kathmandu, to Muktinath pilgrimage site and up into the restricted area of Mustang. For the true ultra-rider, try the route around the Annapurna Massif that includes a 17000 foot / 5400 meter pass!
Bike hire for a half day or full day is inexpensive (but be prepared to leave a deposit or your passport for surety). Tours around the Kathmandu valley run from US$ 50 to 100 per person per day. Outside Kathmandu rates are US$ 100 plus per person per day. Most trips are priced for four people. They are possible for a solo or a small group, but at higher cost.