hola crazydog

there's actually quite some information to find on the internet. One of the best sites occupying with cycling in Tibet/Himalaya is Janne Corax' Page.

I haven't been to TIbet or Nepal myself yet, but also been occupied with Tibet issues during the planning for my trip. What information do you need exactly?

Let me try to give you some basic information about this topic according to my knowledge:

1. It could be that it is impossible to cross the border into Tibet from Nepal (some rumors say so), I believe you have to sort this out by yourself
2. Even if the border is open, it can become tricky, if you want to ride your bike all the way from Nepal into Tibet, as you will probably have to travel as a group to cross the border successfully (Although some people seem to have managed it by themselves at times...)
3. The Friendship-Highway (that's the name of the Road leading to Lhasa) is one of the mainroads of motorized Tibet-tourism. This means, people along this road have mostly been spoiled by dumb landcruiser tourists giving money and other stuff to them thinking that they would do somthing good for them. So you might encounter some hassle...
4. Not sure if this is also the case if you approach Lhasa from south, but I believe that there are some PSB Checkpoints that you have to cross before you come to Lhasa. Some of them at night, or early in the morning.
5. You will probably have some encounters with wild dogs

You might consider to get yourself a copy of this book: Tibet Overland

PM me if you have further questions.

See ya,
Andreas