Here are my thoughts on XC tires:
Rolling resistance makes alot more difference than weight as what is faster.
Avoid really light tires. They don't hold up.
Avoid tires with low profile knobs or continuous center tread, they are typically purpose built for buff hard pack and give up too much else where.
Any tire can be an XC tire. However, purpose built XC tires are typically For Race Only.
A bit bigger casing with real knobs will still hookup even if you botch a line or come in a bit hot on a loose corner. As you progress your riding, you learn to work your tires and can get away with a tire with less grip to go faster. If you are pushing yourself to learn in technical terrain, you want something that is going to bail you out, not smack you down.
Tires worth trying:
Panaracer FireXC 2.1 The standard for cheap xc tires. Light, fast rolling, good tread design. Small for a 2.1. Tire compound is lacking imo.
Specialized Purgatory 2.2: One of my current fave trail tires. It rolls fast and gives good grip on many surfaces. Spesh says they are built for wet loamy trails. So I expect they would work better east coast than here. And here, I really like 'em.
Maxxiss Ignitor: never tried them but hear alot of good stuff. Supposed to be light, fast, and have good grip. Seem to be available cheap as well.
Hutchinson Barracuda 2.1: I use this in a 2.3. Its really confident on technical trails and still rolls fast. Outstanding traction, braking, cornering. Plenty of casing / compound options available. Sorta pricey.
Edited by tromano - 9/20/09 at 11:04pm