Ride Quality
Specialized knows about making quality aluminum frames, with the M4 aluminum featured on the Fat Boy pre-dating the first Fat bike. The M4 aluminum is renowned for quality, lightness and stability. It is plenty stiff for out of the saddle climbing, but also reasonably compliant for when the tire pressure is maxed out, the ride quality is high. The RockShox Bluto front suspension fork is a nice feature, with 80mm of suspension, it helps level out chattery snow and rocky trails. Crown mounted adjustment is adequate when needing to make a quick switch. 

Stiffness-to-Weight/Power Transfer
The Fat Boy Trail Pro is nothing if not stout, which materializes on the scale at 33 lbs. The aluminum frame does not torque or twist, though the added heft is evident on the climb. Not the most climbing focused Fat machine we tested, the Fat Boy adequately makes its way along the climb and provided you remain seated, won’t slow you down (too much). The Race Fact Next SL cranks are a stiff and able, and the wide aluminum bars and short stem make for a comfy cockpit. The overall positioning seems a bit forward as grab of the rear tire traction was lacking in certain situations causing rear wheel slippage.  

Climbing/Efficiency
The Fat Boy Trail Pro is intended to be a trail riding machine, and it has the characteristics one would associate with a trail bike. A stiff platform featuring a wide Specialized aluminum bar (8 degrees back, 6 degrees up), on a short stem and the Race Face Next SL direct mount cranks with 28T chain ring enable comfortable and reasonably efficient climbing. The drag results from the large tires and heftier set up and the challenges getting good tire hook-up on slipperier surfaces. In fairness, conditions vary widely day-to-day when riding snow and dirt, and tire pressure modulation is an evolving art form on these bikes with different tire sizes and geometry. 

Descending/Handling
Wide bars, 100mm of suspension, aluminum frame on 26 inch wheels with Specialized Ground Control tires: is it the 90’s again!? If so, we’re not complaining—dropping in on this bike is a blast. Massive traction on the Ground Controls makes for ridiculous cornering abilities and the suspension is adequate when combined with the substantial cushion provided by oversized wheels and tires. XT brakes continue the downhill joy, where true single finger effort is enough to stop even this substantial, enjoyable bike.

Components: Drivetrain, Shifting and Brakes
XT brakes and levers are a joy to ride. Quiet and sharp, minimal grip strength required, little to no fade, they just do the work. SRAM X01 11 speed drivetrain provides adequate spread and quality shifts. It’s easy to get topped out on a long down hill, but appropriate for the climb (28 tooth up front, 10-42 SRAM X1 on the rear). Command Post Black Lite dropper post comes with the bike. A nice touch, and a light touch bar mounted remote adjust comes in handy. The Command Post is the most consistently functional dropper we’ve tried. 

Wheelset
Specialized Stout XC 90 32 hole hookless design for the rims spun on Specialized Stout double sealed bearing hubs are an appropriate spec for this bike. Not the lightest set up, but perfectly enjoyable and performance oriented. The Ground Control 4.6 inch foldable tires are top notch for mixed surface riding. 

Value 
At $4,200 the Fatboy Trail Pro is a reasonable value considering you get front suspension and a dropper.  Although the frame is heavy and many would expect carbon for this price.