From your posts it sounds as if the first half of the trip is on gravel and the second half on pavement. If you are not going to be switching back and forth between the two and only make the change once at half way I would consider carrying a second set of foldable tires for the pavement. Put the biggest tires you can fit for the gravel and some 26x1.5s for the pavement. Trying to use a tire that works for both will work for neither very well. It would be nice to have 2.1 or bigger on the gravel and a 1.5 that can handle 85 lbs pressure on the road.
The bigger, lower pressure tire is not going slow you down on the gravel. It will be safer and allow you to ride more relaxed. You can also adjust the pressure to the conditions. Most big MB tire can range from 35 to 65 lbs.
Carry a good pump for adjusting pressure!
Last edited by sedges; 12-11-11 at 03:37 PM.