Mountain Biking In Nepal

Mountain biking is a fantastic way to explore Nepal. The allow you to travel independently and stop where ever you want. You do not have to tortuous buses. You can explore secluded places and reach places that cannot be visited any other way.
Nepal has many trails to ride on. You can make a challenging climb thousands of metres to reach a viewpoint with fantastic views. Then you make an exhilarating descent. It is an interesting trip ride to Royal Chitwan National Park.
The long bike tours require that you are physical fit. Unless you plan to ride along a trekking route, there is no required paperwork. To do any serious biking you need a mountain bike, and a normal bike will not do.
The Kathmandu Valley has some great places to ride. It has many trails and back roads. It is a good way to visit the interesting towns, temples and Buddha stupas. It can be really interesting visiting a rarely visited traditional Newari village. To get around the valley you most likely will want a good map, such as the Schneider or Nelles Verlag map. Most of the other maps are not very good and are often inaccurate.
Many trails are not on maps and you will need a good sense of direction and will have to stop and ask directions to get around. A little Nepali can really help.
Clothing Warning Tight fitting Lycra clothing, especially if worn by women, will not be well accepted by the local people. It shows too much of the body. It is better to wear shorts and a loose T-shirts.

Equipment
If you plan to ride to a really lot of riding, it would be a good idea to bring your own bike. Good mountain bikes can be rented in Kathmandu. A bike can be put on a flight as part of your baggage allowance. You have to deflate the tires, remove the pedals and wheel, and have the handle bars parallel with the frame. There is no problem to bring a bike to Nepal. If you bring a bike you should definitely bring tools and spare parts, as you are unlikely to find parts in Nepal. 
It is a good idea to have a bell on your handlebars, as there are often many people on the roads and trails in Nepal.
Himalayan Mountain Bikes in Kathmandu are good at repairing bikes. Often they can repair foreign bikes and can substitute spare parts.
Most of the bikes rented in Nepal are low quality Indian made bike, which are not durable enough for trail riding. Usually rental companies do not rent luggage racks, helmets and spare parts.
You can rent good quality imported from some travel agencies.

What to Expect on the Road

Usually might is right on the roads and the bottom of the barrel are bikes. If you and a bus are heading for a head-on collision, most likely you are going to lose, so it is more important for you to get out of the way. It can get very hectic sometimes on the road with all kinds of vehicles, people and animals going every which way.
The pollution in Kathmandu is getting really bad, so if you have a problem breathing you should consider bringing a mask.
You should be careful around a village not to hit someone who is walking, especially children. Children can run out onto the road at any moment. If you harm a child you will definitely be considered wrong and be beaten up or worst.
You should be careful when passing animal such as cows, buffaloes and dogs, as they can be very unpredictable. A cow can lunge at you for no reason at any time. If you hurt a cow the local will not appreciate it, and regardless what the cow did, you will be considered in the wrong.
To avoid long up-hill rides and to avoid areas with a lot of vehicle traffic local buses can be really helpful. You can put your bike on top of the bus for Rs 40 to Rs 100, depending on the length of the journey. You should have rope or something to make the bike secure. You should have it lie as flat as possible so as not to catch any low wires or tree branches. You should watch your bike being loaded, so it is done in the gentlest way to make sure it is not broken. Do not believe for a second that it will be done properly without you watching it.
If you plan to take a bike along a trekking route you may find that you have to carry the bike up to 75% of the time. There are often trekkers, porters and animals on the trail and will make it hard to get around.

What to Bring

These are some items you may want to bring
A helmet, cycle gloves, light clothing (Gortex or Coolmax), sunglasses, cycling clothing, bike bell, water bottle, sun screen, rain jacket, warm hat, iodine tablets, first-aid kit, electrolyte powder, flashlight (torch), bike chain and lock, pollution mask, windbreaker, sleeping bags, bungie cords (shock cords), tire repair kit, spare inner tube, tool kit, pump, spare parts, sweater and good shoes. Sleeping bags and tents can be rented in Kathmandu.
Pollution (face) mask can be purchased in Kathmandu.
Spare parts for the bike, inner tubes, and patches and a small pump.