I'm touring across the US this summer (west - east) along a modified version of the northern tier route. In planning my route I'm finding that many times I can avoid numbered "Rt" roads (i.e. Rt 84, Rt 191) by taking side roads. This also cuts down on my total distance and since I am somewhat pressed for time, I like the idea of saving 20-30 miles in certain locations. The biggest concern (aside from getting totally lost) is that the smaller roads tend to avoid towns and would miss possible supply stations. If I plan right, I imagine this won't be a problem but I've never done a tour of this magnitude so I welcome other people's opinion.
Here is a link to an example in Montana http://www.google.com/maps?f=d&hl=en...,1.315613&z=10
For those who have toured long distances, do you recommend sticking to the larger roads or have you found the lesser, more direct roads to be suitable? I know there are a lot of factors to consider but try to only speak to the idea of larger roads (less direct) vs smaller roads (more direct) and the issue of supplies.