I bet that Trek is a blast on gravel!
We rode quite a few unpaved forest service roads down south this spring, and even with our MTBs, there were squirrely areas. And with our Bike Fridays (1.35" tires), they were downright scary in spots, as you experienced with your Salsa. They do great on the hard-packed gravel, like the Katy Trail, but when the surface gets loose...no.
Emily
2011 Jamis Dakar XC "Toto" - Selle Italia Ldy Gel Flow
2007 Trek Pilot 5.0 WSD "Gloria" - Selle Italia Diva Gel Flow
2004 Bike Friday Petite Pocket Crusoe - Selle Italia Diva Gel Flow