congrats on getting into leadville !
we did it on the tandem last year... I had done it once before that solo as well.
Tires: FAST. Unless it is very wet, the fastest rolling tires you can find will work well... but make sure they have some volume to them for the tandem. We used continental race king 2.2s last year and they were absolutely perfect for the conditions... light and fast rolling, but still relatively high volume. We ran tubeless on front and a tube in back... but only because I couldn't get a reliable seal on the rear that I was comfortable with. I guess I should also mention we are on a fandango 29er.
Hydration: in endurance races hydration and nutrition are of paramount importance. We both used camelbaks.... and we started with one bottle each on the bike as well. We rolled through aid 1 at pipeline without stopping, then stopped at twin lakes outbound and picked up bottles.... so we started the big columbine climb with half full camelbaks and 2 full bottles each on the bike. we grabbed 1 bottle each at a quick stop at twin lakes inbound.... then took a longer stop at pipeline inbound for another bottle and stoker refilled camelbak. There is one other non-official aid station at the top of st keevins inbound, but they only have water... we took full advantage of that and grabbed a bottle each to get us to the finish from there.
The aid stations are great and have everything you need.... but can get VERY crowded. If you have your own crew, you can get in and out of the aid stations much faster. there is actually a "crew only" aid station just before the start of the columbine climb.... this is the place to set your aid up if possible in order to avoid the huge crowds at twin lakes...
If you go to this page:
http://www.leadvilletrail100.com/lt100races/LeadvilleTrail100MountainBikeRace/results.aspx
you can see the full results sheets. The time check points are the aid stations... so you can get a really good idea of how long it might take you between the various aid stations if you look for riders who finished around your expected time.... I believe time between aid stations is much more relevant than distance between them.
hope that helps a little
andy applegate