The Idea:
For many riders, including myself, the best time of year to mountain bike on the local trails in Bend, OR, is after the first few rains of early Fall. Cooler weather combined with the added moisture keep the trails firm and tacky, making for the ideal rubber-to-ground contact.  Technical climbs become a little easier, confidence brews on fast corners, and riding with friends is simply more fun on dust-free singletrack.  The problem is that as the days grow shorter, there is less and less time to ride after the work day.  This used  to push mountain biking to a weekend activity come Fall-- not anymore.
While night mountain biking might seem like a masochistic, peripheral sporting endeavor, the fact is that with the advent of new generation, affordable, and bright LED bike lights, even beginning-intermediate mountain bikers can enjoy trail riding after dark.  The longer days of summer used to be a mountain biker’s best friend—get caught on a trail after dark, and the chances for a hard fall or having to walk your bike back to the trailhead start to rise.  Alas, the new, lightweight and fast charge LED mountain bike lights extend the mountain biking season into October and November, and if you’re an avid mountain biker, help alleviate the doldrums of the nine-to-five.  I now begin rides in mid-October at 5:30pm during the last hour of daylight and segue seamlessly into an after-hours adventure-- the lights are bright and the fun doesn’t stop until I get back to the trailhead. 

The Light:
My trail light of choice is the Princeton Tec Switchback 2 (www.princetontec.com).  The Switchback 2 offers a burn time of over five hrs. on the high beam setting (the best choice for singletrack riding) with two, blinding three-watt LEDs.  Amazingly, the rapid-charge Lithium-ion battery is ready to roll after only two hours of charge time.  Although Nite Rider’s Tri-Newt light (www.niterider.com), another good choice for serious night riders, is slightly brighter, the accessories and the price of the Princeton Tec make up the difference-- and then some. The Switchback kit includes a car charger, helmet mount/ bar mount, helmet extension cord, and other tech treats that add up to the most complete mountain bike light kit on the market.  The price is right at $270.00 retail, compared to $550.00 for the Tri-Newt.  The car-charger for the Tri-Newt costs extra.

The Ride:
My first night ride with the Switchback 2 came during an after-work training ride with my boss, who also used the Switchback 2.  As day faded to night, we turned on our lights halfway through our three hour ride. Clicking the lights into the user-friendly helmet mount was easy and the pre-coiled, stretch extension cord connected the light and battery pack flawlessly.  The battery packs stayed put in our packs. 
The Switchback kit includes both handlebar and helmet mounts.  The helmet mount is my first choice over the included handle bar mount, as it gave me the control of looking where I wanted to ride without having to rely on the orientation of the handlebars for light direction.  After trying both the helmet mount and handlebar mount, the difference is pronounced on switchbacks and corners on the trail.  The helmet mount lit up the corners with just a slight rotation of my head.  Ideally, I would have the dual beam Switchback 2 mounted on the handlebars, and a single beam Switchback 1 mounted on my helmet—but that’s another review.
The weight of the light on our helmets was negligible as the mount is strapped to the top and center of the helmet nullifying any sag or discomfort from the added weight.  It was worth the time fitting the mounting strap to the helmet and adjusting the light before the first ride.  A quick peddle around the driveway was all it took to get the right fit and beam angle.  Trailside adjustments of the beam angle are a breeze.
The Switchback 2 lit up the trail even before the fading, wispy light left us in the dark.  The dual 3 watt lights shot a beam down the trail just far enough that I could maintain a pace nearly as fast as daylight riding while on flat terrain.  High speed descents were a tad scary, however, and required a slower pace, but hey—it’s night mountain biking.  The light emitted from the Switchback 2 is bright and crisp.  The only negative about the light output, was that soft dirt tended to blend in with hard-packed trail, requiring extra, on-your-toes attention during those sections.  This seems endemic to any night light system, and really only matters during the summer months when some trails tend to hold a thick layer of dust.  My night biking season starts after the rains when the days are shorter, so this shouldn’t be an issue in the future.
We chose a ride with a lot of smooth single track, trying to keep the rocky, technical sections to a minimum on our first ride with the Princeton Tec lights.  On the few technical patches of trail, the light was more than adequate, although as the light moves down the trail, rock shadows elongate and contract, adding to the challenge.  I’ll stick with low-tech trails in the future.

Bottom Line:
The Princeton Tec Switchback 2 is now my shoulder-season riding partner.