Design
The cutting-edge, wind-tunnel tested aerodynamics make this the most technologically advanced box on the market.

The most distinguishing characteristic of the Sonic Alpine is the patented, dimpled nose of the box. Taking a cue from the golf ball, the Sonic’s nose is covered in knuckle-sized dimples that help move air up and over the box—and Thule wind tunnel tested the box to prove it. It’s not a cheap surface to manufacture, hence the premium price attached to this model.

Thule even considered the box’s attachment clamps in terms of aerodynamics: instead of using bulky hardware, the Sonic holds tight to the crossbars with four thin, air-slicing claws.

The Sonic features a dual-sided entry, which is a godsend if the box is centered on the cross rails. The lock is simple and easy to use—one of the easiest I’ve ever seen.

Installation
Thule’s installation was incredibly easy. It took me all of 5 minutes to pull the box out of my garage, throw its 36-pounds up onto the roof of my minivan (I’m a 6’3” male), open the box, unscrew and position the four claw clamps around my crossbars, and screw the clamps tights. Like a car’s gas cap, the screw makes an audible click when it’s been tightened enough. I was blown away. Removing the box took me all of 2 minutes.

The ease and speed of the Sonic was a game-changer for me, as well as the fact that it fit inside my garage. This may be the one cargo box I actually use regularly instead of storing away and only bringing out once a year for big multi-day road trips or car camping.

It’s relatively light, the top cover is structurally solid, but the bottom portion flexed more than I imagined it would—especially for a $600 cargo box. The box’s 110-pound weight limit, however speaks to a tough box.

Cargo
The price for Sonic’s superior aerodynamics was its limited cargo capacity. With only 11 inches of height inside, I felt limited to one layer of skis/snowboards, instead of the option of stacking them like I could with the others. Also, the big hand screw knobs on the clamp assemblies eat into the box’s usable floor space. Still, with some trial and error, I could see how 4 pairs of adult skis in the box and poles would fit. Snowboarders shouldn’t have any trouble fitting 3 boards and 2 pairs of boots inside.

In the summer, the box would easily hold such space hogs as sleeping bags, tents, sleeping pads, and pillows.

On the Road
As expected, the Sonic shines on the road, particularly in crosswinds where its low-profile shines. As for its effect on fuel economy, the difference was small enough that I suspect that my driving style and routes were having more effect on mpg’s than the box.

Value
The upfront cost is considerably more than the competition—even Thule’s other offerings—but the argument could be made that leaving the wind-slicing box on the roof of the car for the duration of ski season, with its weekly 150 to 200 mile round-trips to the ski hill, could leave a person coming out ahead in terms of gas savings over traditional models.

Vehicle Fit
Due to its super-long length, the Sonic isn’t ideal for small hatchbacks or sloping rear window type vehicles; the rear overhang will prevent the hatch from opening. Best save the Sonic for SUVs, wagons and minivans.