Under no circumstances would I buy any backpacking gear during your trip, as one poster suggested. It will all be a knock-off. You will see great prices on lots of North Face (or as one tent we saw said--North Fage), etc, items during your trip and while it is very non-expensive, if you buy any of it you'll soon know why.
That said, while I didn't do any camping in China, My girlfriend and I used our Bibler Eldorado in Tibet to great effect. Depending on the season of your trip (I went in October) you can easily get by with a three season tent--and this would be much better for you in China. We aren't climbers, just long distance backpackers, so the highest we camped was 16,000' and we only had a dusting of snow a few nights, but it was QUITE cold. I would recommend a tent that can be closed up to offer some privacy from the locals, especially kids who are bored and will literally hang out at your tent for HOURS. And get a tent that can hold all of your gear inside (not including the vestibule) as anything outside is fair game to get stolen--especially shoes. Even though you are cycling, you still may find some useful information from our trailjournals report: www.trailjournals.com/teamnasty
If you really really need help on your planning, we met two fantastic guys from Canada who rode from Lhasa to Kathmandu and had a fantastic time (although one came down with hape after our flight from Chengdu, an 11,000ft elevation gain in 2 hours) and I could try to track down their contact information if you like.
Good luck on your trip and better luck on getting into and around Tibet. I don't know how politically minded you consider yourself, but we would recommend patronizing only Tibetan businesses (as opposed to Chinese businesses). We used the tourist services at the Banak Shol hotel (which was super nice and all Tibetan run--as of 10/06) and stayed at the Yak Hotel (also Tibetan run). The old quarters of Lhasa are a great place to meet fellow travelers and compare travel plans (almost everyone we met had no idea what we were doing as none of us were using guide companies and we all used a week in Lhasa to acclimatize and see the Lhasa sights while finding out what the current permit situation and tourist restrictions were (they can literally change daily). A word of advice--due to the internet police there and no access to any website with the words "freedom, dalai lama, etc", we had to have a lot of our friends in the states do last minute research for us while we were in Lhasa and they then emailed it to us. It is technically illegal to go outside of Lhasa without an approved guide, so you may have to sneak past some guard checkpoints at nightfall or bribe your way past them. Again, I'm sure restrictions are much stricter now due to the recent turmoil there, but our thought was that paying tons of bribes was still cheaper than buying the actual required permits (no permit $ goes to Tibetans) and risk getting those requests turned down.
One last thing--I'm sure you already know this--do not mention Tibet when applying for your Chinese visa.
Sorry to go off topic a bit, but all these memories are coming flooding back. It was literally the most beautiful and the most logistically challenging place to visit. Can I ramble or what?