I can tell you the exact moment I decided that roof racks on four-wheel-drive vehicles should be, 1) left off if possible, and, 2) loaded as lightly as feasible if not.

I had to ferry a cased, rigid-floor 14-foot Zodiac inflatable and a Yamaha outboard motor to a research station in Mexico from Tucson, using my 1973 FJ40. Neither boat nor motor would fit inside, so I decided to strap them on the roof rack—where, I noted with satisfaction, they looked purposeful and very, very stylish. Thus with almost exactly 500 pounds of equipment—in addition to the 100 pounds of my reinforced Con-Ferr rack—secured seven feet above my 90-inch wheelbase, I headed south. And all went perfectly well—until, on the apex of a blind right-hand curve, I discovered a very slow-moving cow in my lane. 

Having successfully circumvented that cow—and with the Land Cruiser back on all four wheels—I decided, Okay, this is dumb. 

It’s natural when you’re just starting out to want your vehicle to look like a proper expedition machine, and to a lot of us that means a roof rack, probably further enhanced with a bank of driving lights, a few NATO jerry cans, those awesome perforated sand tracks, a Hi-Lift jack, a Pelican case or three, and perhaps a roof tent. After all, for our inspiration we have those inspiring images of the Camel Trophy Land Rovers, high-mounted Bosch driving lamps blazing, forging paths through the jungles of Papua New Guinea or the black cotton soil of Tanzania. Those Range Rovers and Defenders and Discoveries remain unsurpassed as the epitome of expedition cool.

Two things are important to remember, however. One, the CT vehicles were navigating remote areas of the planet and overgrown tracks in stunningly bad conditions, and required huge amounts of recovery and survival equipment. Inside the vehicle were always two team members plus at least one journalist, so much kit simply had to go on the roof. And, two, those Land Rovers ended up on their sides very, very frequently in the midst of Special Tasks requiring greater than prudent speeds.

Any weight above the center of gravity of your vehicle tries its best to tip it over in the midst of an emergency maneuver, or at low speed when tilted on a side slope. And good old Newtonian-esque laws of mass, leverage, and velocity are always conspiring to do their worst. Two hundred pounds of driver sitting a few inches above the CG exerts much less force than 200 pounds of gear sitting a foot above the driver’s head. Excess weight on the roof affects braking as well. When the brakes are applied sharply, the weight on the roof tries to tip the vehicle over forward, unloading the rear tires. Modern ABS systems will prevent rear brake lockup, but braking distance will still be compromised.

So far we’ve only discussed handling and safety. But a roof rack and its load hugely affects windage as well. My FJ40 gets exactly one mile per gallon more without a roof rack than with it mounted. That might not sound like a lot, but the difference between 16mpg and 17 adds up—and this on a vehicle with the drag coefficient of a Motel 6. Imagine the effect on a modern, aerodynamic SUV. 

All well and good. But what if you simply cannot fit all your gear inside the vehicle, because you, a) have a spouse and two kids, or, b) a very small vehicle, or, c) just too damn much stuff? An obvious solution presents itself for (c), but let’s discuss the other situations. If you decide you really need or want a roof rack, it’s smart to go with the lightest one possible that retains the rigidity you need. It also makes sense to go for the lowest profile possible, so that when it’s not loaded with gear it creates the least amount of windage. Front Runner, among other companies, produces low-profile aluminum models that are lightweight but exceptionally sturdy. Then decide if you really need a full-length rack, or if a half-sized rack would suffice, mounted well behind the air flow coming up the windshield. 

As to what to put up there, choose the light but awkward items that take up the most room inside—camp chairs, tables, bedding, for example. How much is too much? It depends on numerous factors, of course, high among them the weight of the vehicle itself. Two hundred pounds on the roof of a Suburban will affect it less than 200 pounds on a RAV4. If you need a rough guide, try to keep the weight of rack and gear to significantly less than five percent of the curb weight of a vehicle with no suspension lift. On a 4,500-pound Jeep Wrangler Unlimited, for example, that would give you enough leeway to mount a Front Runner rack and a two-person roof tent without dangerously affecting the handling—although I guarantee you will feel the difference. 

Then, please skip the Pelican cases and jerry cans, okay? 

All images courtesy Peter Sweetser, Camel Trophy Owner's Club