The Indian Himalayas offer great trail and dirt road riding, Tibetan Buddhist monasteries, and inspiring scenery. It's great bicycle touring for mountain bikes. There's also a sag for much of it: a bus comes on dirt roads and you can load the bike on top. Roadside tent restaurants and tent hotels provide convenience, but don't depend on them. Storm possibilities require bringing a tent and 2 or 3 days of dry food. Safe water means bringing both a water filter and iodine.
Of great interest are the Tibetan Buddhist monasteries, often situated on cliff faces. We visited nine. These monasteries are the best examples of Tibetan monastic life, since almost all the monasteries in Tibet itself were destroyed. In Zanskar, a former independent Tibetan kingdom only opened to foreigners in the mid 1980s, many can only be reached by trail. You are going back to medieval times. There is no electricity, just candles of yak butter. The walls of each of the many chapels in the monasteries are painted in religious themes, including explicit erotic ones. The monks are glad to get visitors. Many speak some English. You are usually shown around by boy monks. You'll probably see some of the ceremonies and hear the unusual musical instruments.
The most interesting monastery was Puktal Gompa [monastery], reachable only be two days riding on trail from Zanskar Valley, or 5 days of trail from Darsha. It contains a large natural cave, which is also its source of drinking water. It's on a cliff face. Dark staircases take you from level to level in the monastery. A torrential river way down below is seen when you look out of a window or balcony. The top floor, as in all monasteries, is the holiest point. Continuous chanting in very deep tones, and rhythmic deep drumming, emanates from there. You can observe this praying, which also contains movements of various ritual objects. The first European to this region, a Hungarian named Csoma Sandor, thought it was an variant of Catholicism!
Monasteries offer "hotel" and "restaurant" service. This usually means sleeping and sitting on the floor, as they do. The food and tea they cook for you is edible, but their staple consists of rancid, salted yak butter tea --no, you can't leave out the rancid yak butter-- and tsampa, a barley and rancid yak butter mixture with the consistency of clay (and often played with). There's no hot shower, just cold running water.
Elevation averages 12,000 feet average if in inhabited areas. We crossed five passes, three over 16,500 feet, the highest being 17,600 feet. The Himalayas are actually 3 mountain ranges in this region. The first two contain glaciers, ice falls and large waterfalls, like in Yosemite. The last range is bone dry, but is colorful, similar to ranges surrounding Death Valley. We had no trouble with the altitude, since it takes days to get up that high. Remember to hyper-ventilate after you stop exercising, but you'll soon get in the habit.
We spent five days continuously at over 15,000 feet, riding from the Ladakh Valley to Darsha. There's no village in between, just nomads and a few roadside tents. You'll observe a huge spring the size of a creek flowing from a cliff. But note: there is no water for 50 km on the south side of the 17,600 foot pass late in the season, when we went.
A possibility for trail riding, which we took advantage of, was to hire a Tibetan horseman to take the panniers. For two days, we even had the horses take the bikes over the Shingo-La [pass]. It's only $7 per day per horse. The horseman is free. He's also your alarm clock, chanting "Om mane padne um" for the first hour of every day. This would be an ideal way to the Zanskar Valley, the most primitive and the most interesting. I recommend reliable front shocks because many trails and even dirt roads are rocky.
For doing your own tour, I recommend the guide "Ladakh and Zanskar", one of the Lonely Planet series. From New Delhi, take an express bus (with your USA brought bike on top) to Manali, a comfortable resort town where we acclimatized. It was our last hot showers and TV (with CNN and BBC) until we returned 4 weeks later. From Manali, it's a scenic one-day ride to the first pass, which doubles your elevation to 13,000 feet. Darsha is a village where we left the (mostly dirt) road, and the last place one can buy supplies: oriental noodles, Canterbury chocolates, cookies and crackers. There are no more stores until reaching either Padum in Zanskar, 7 days later on trail, or the Ladakh Valley, 5 days later on dirt road. You should also bring freeze dried food from home. In Darsha you can rent horses, as we did. In total, our trip was 1200 Km long and took 4 weeks.
Do not travel through Srinagar and the Kashmir Valley to get to Ladakh (the only paved road) because of a Moslem insurgency and ultimatum against foreigners, that all who enter will be executed as Israeli spies. As a result, flights to Leh (capital of the former Ladakh kingdom) are booked up months in advance. Go through Manali and Darsha, instead. This route has been open so recently to foreigners that the guidebook still states it is closed. An alternative to your own tour is a fully supported bicycle tour group (that we encountered) with great food and filtered water provided: Himalaya Trek, 7504 Pontresina, Postfach 136, Switzerland.