First of all US News have more than top 50. "Tier 2" means 51-100 or something like that, and so forth. They also have a "more rankings" section.
In tiers you have to look at this bar and compare the "reputation score" (the first columnn)

You can also check out the Princeton Review site for more unconventional ratings: http://www.review.com .
I couldn't make this link work, sorry. Click on College search>The Rankings.

This is the longest answer I'm ever going to give anybody, because of all this HTML.