Jamis bills the XAM II as an "aggressive all-mountain" bike, a designation this baby blue beauty had no problem living up to. Witness the headtube-downtube junction: a triple-decker-submarine-sandwich-sized mass of 7005-aluminum tubes and gussets. In fact, everything on the frame, from the massive chainstays to the oversized swing-link and shock mounts, is seriously overbuilt.
Spec-wise, the bike is smothered in blingy-but-durable components. Highlights include the excellent Fox 36 TALAS-RC2 fork, Avid Elixir CR brakes, Fox DHX Air 5.0 rear shock, SRAM X.0 shifters and rear derailleur, and Truvativ HammerSchmidt all-mountain crank.
Given all the burl, I was immediately surprised to find that the XAM II is a reasonably able climber. No, it doesn't scoot up mountains—no bike that weighs 34 pounds scoots up anything—but it doesn't bob excessively, either.
Jamis contends that the XAM II's rear axle path is nearly vertical, which should minimize chain growth and pedal kickback on big hits. I did, however, experience a bit of backward tugging on the pedals during extremely rocky climbs. The lumpy pedaling sensation isn't a deal breaker, but it was occasionally annoying.
Of course, the XAM II is primarily designed to go downhill, and for the most part it excelled in that department. The stout frame felt absolutely bombproof in rough terrain. Big kudos go to the excellent components—particularly suspension and the HammerSchmidt—the last of which banged off hundreds of shifts with uncanny speed, survived a good number of rocks, and produced nary a hiccup despite months of use.
There are a few things about the bike, however, that could be improved.
First, the XAM II's standover height—a rather tall 32 inches on our 19-inch test bike—and relatively high 13.46-inch bottom bracket made maneuvering the bike through technical terrain a mite dicey. My other complaint is about the head angle: at 68.5 degrees it's a bit nervous on drops and punishing, near-vertical terrain. Slackening the head angle just a degree would improve things immeasurably. Admittedly, the same steep head angle also helped keep the front wheel planted on climbs and gave the bike surprisingly agile, dare I say "cross-country" handling on tight, twisty singletrack.
And then there's the price tag. True, the parts are stellar, but I'd expect the XAM II to shed a few pounds at this price point—after all, it's competing in a market full of excellent, 6-inch-travel bikes that weigh less than 30 pounds. Still, I was impressed with the XAM II. It's one of the rare bikes that really embodies the "all-mountain" category: strong and versatile enough to be ridden almost anywhere.