Is Gross Vehicle Weight Rating . . . Overrated?

We all know most of America is overweight these days. But 2,000 pounds overweight? 

Scott Lesak wrote us regarding his 1997 Mitsubishi Montero (the one in front here), which he has outfitted extensively for overland travel (his brother Mark owns the one following). Recently, Scott weighed virtually every piece of gear that goes into the Montero for a typical camping trip, and after adding in the curb weight of the vehicle, plus occupants, was concerned, if not really surprised, to find the total nearly 2,000 pounds higher than the factory’s listed 5,700-pound GVWR (Gross Vehicle Weight Rating includes empty vehicle weight plus all fluids, occupants, and cargo). He wondered if by carrying that much excess weight he was, a) risking damage to the vehicle, and, b) compromising safety on the road through reduced braking performance, etc.

To which, of course, the short answer is yes and yes. 

If you’ve never weighed your own vehicle completely kitted and fitted for an overlanding trip, you might wonder how anyone could wind up a ton over the maximum recommended weight for a sturdy 4WD vehicle such as a second-generation Montero (which has a 1,300-pound cargo capacity including occupants). Trust me, it’s not that difficult. In many cases, the weight of just the modifications we bolt to our vehicles can come perilously close to topping the GVWR, before a single down sleeping bag gets tossed in the back. Look at Scott’s list of his own modifications: 

150 lbs for upgrade to 35-inch tires

150 lbs for (empty) Garvin 84-inch roof rack

300 lbs for ARB bumper and 12,000-lb MM winch

200 lbs for custom rear bumper and swing-out mount

100 lbs for custom skids under transmission & transfer case

60 lbs for 15-gallon (empty) auxiliary fuel tank

100 lbs for rock sliders

80 lbs for extra AGM battery (105 amp hour; big and heavy for a 2nd battery)

100 lbs for custom drawer system (empty)

20 lbs for ExtremeAir compressor

50 lbs for fridge slide

80 lbs for Engel 60 freezer fridge (empty)

45 lbs for cargo barrier

25 lbs for 84-inch roll out awning

35 lbs for Hi-Lift Extreme jack

Remember that 1,300 pound cargo rating for the Montero? Scott just blew past that by almost 200 pounds—and he hasn’t loaded a single item of camping gear. Or fuel. Or himself. Let’s look at the rest of his list.

200 lbs for 25 gallons non-potable water for showering/cleaning

80 lbs for two 5-gallon jerry cans of potable water

92 lbs for 15 gallons fuel in auxiliary fuel tank

123 lbs for fuel in main tank

60 lbs clothing for 4 persons for 5 days

30 lbs for storage box #1 containing propane grill/heater and various accessories

40 lbs for storage box #2 containing cookware, electric coffee pot, dry food items

40 lbs for 4 sleeping bags, towels, pillows

20 lbs for 4 folding chairs

20 lbs for tent/awning mosquito net/folding table

20 lbs for firewood

10 lbs for propane tank

5 lbs for axe/sledge

700 lbs for passengers

40 lbs for hiking pack

60 lbs for gear in drawer (hoses for shower system, chains, recovery straps, 1 qt engine oil, 1 qt trans fluid, Hi-Lift attachments, basic tools, air hoses for tires/air mattress, lantern, fire ring, 1200 watt inverter)

20 lbs food/drink in the fridge

10 lbs cold weather clothing/rain gear suits

That’s another 1,570 pounds of people and stuff. And while it’s certainly comprehensive, there’s nothing in the entire list that’s really out of the ordinary for a vehicle set up for backroad exploration and camping with a family in mind. But what about unforeseen consequences from all that weight?

Every vehicle has a GVWR, or Gross Vehicle Weight Rating, specified by the manufacturer. The information is usually on a sticker on the edge of the driver’s door or door frame, as well as in the owner’s manual. There are dozens of factors that can be used to calculate GVWR, which isn’t to say that all manufacturers use the same list. Most obvious is the suspension, including spring rates, shock valving, anti-roll bars, etc. Braking capacity is another critical variable. Chassis design, wheel and tire size and rating, engine horsepower and torque, transmission capacity, differential gear size and ratio, driveshafts, axles, wheel bearings, CV joints—all these and more contribute in some way to the vehicle’s capacity to haul a load. Whether or not they’re all included by the manufacturer, they should be considered as an interdependent system by the owner.

You might think fear of litigation would drive manufacturers to be conservative regarding GVWR, but, particularly when discussing pickup trucks, advertising trumps reality. If your pickup has an 8,000-pound GVWR, and the brand across the street boasts a 8,500-pound GVWR, that makes your truck look puny in the one-upmanship game with which the American truck market is obsessed. So just because your vehicle is rated to carry 2,000 pounds of cargo doesn’t mean it can do it comfortably—or even safely. As an example, our 2000 Toyota Tacoma Extra Cab with the TRD package was rated to carry 1,400 pounds, if memory serves. Yet with nothing but an 800-pound Four Wheel Camper in the bed the rear end sagged alarmingly, the headlights lit up bedrooms in third-floor apartments, and we negotiated corners looking like a sailboat rounding a leeward buoy. Immediate suspension modification was called for. In our case, a set of heavy-duty shock absorbers and a pair of adjustable air bags handled the situation perfectly.

Scott’s Montero is equipped with a set of custom coil springs, and from photographs they appear to handle the extra load very well. The factory shocks that came on the vehicle are adjustable, and now live permanently in the “firm” mode (brother Mark’s Montero didn’t have that option and rides on Old Man Emu shocks).

Scott also extensively modified the vehicle for better performance on challenging trails. The tires are 35-inch Goodyear Wranglers, significantly taller (and heavier, as noted in his list) than the stock 30-inch tires. To fit them, Scott raised the suspension two inches and installed a two-inch body lift as well. He compensated for the taller tires by changing the differential gears from 4.2/1 to 4.9/1. In addition, the modest stock transfer case ratio of 1.9:1 is now a healthy 3.15:1, giving the Montero a very good 43:1 crawl ratio in 1st/low. The vehicle also has a stock Mitsubishi rear diff lock and an ARB front locker.

On Class 3 and 4 trails, there’s very little doubt Scott’s Montero would outperform a stock one. But how do his modifications, combined with the oversized load, affect its durability and safety as an overland vehicle?

The springs are clearly doing their job keeping the vehicle level and retaining sufficient suspension travel. The next component to consider is the braking system. Scott is lucky in that his Montero came with four-wheel disc brakes, not very common on mid-90s SUVs. Nevertheless, at nearly a ton over GVWR those discs are obviously working harder than they would be in a lightly loaded truck, and there’s no need for a track test to confidently assume emergency stopping distances are increased. And the bigger tires don’t help at all, as they add an enormous amount of rotating mass. I have a study in hand from the American Association of Motor Vehicle Administrators, in which they tested braking effectiveness with successively larger tires on a 1992 F150 Ford standard-cab pickup, in terms of the g-force generated by specific pressure on the brake pedal. For example, 76 pounds of pedal pressure—equivalent to a hard stop—produced .57g of retardation with 32-inch tires, but only .51g with 35-inch tires. With 150 pounds of pedal pressure—a full panic stop—they recorded .68g with the 32-inch tires, and only .62g with 35-inch tires. Since Scott’s Montero’s stock tires were 30-inchers, we might expect the difference to be larger in his case. In addition, the weight of the roof rack and its contents puts more stress on the front brakes in a panic stop, and will kick in the Montero’s rear anti-lock system earlier.

Those larger tires, combined with the suspension and body lift and the loaded roof rack, also negatively affect the center of gravity of the vehicle. In the same study referenced above, the Ford truck was evaluated for Static Stability Factor (SSF), an industry standard for determining the vehicle’s chances of rolling during a violent emergency maneuver. On stock 29-inch tires with no suspension modifications, the chances of rolling were calculated at 10 to 20 percent—low enough to earn the truck a four-star rating (out of a possible five). On 35-inch tires, with a three-inch body lift and a four-inch suspension lift—not at all out of the ordinary on a full-size truck—the chances of rolling went up to 30 to 40 percent, enough to drop it to a two-star rating. And that’s without a loaded roof rack. (I doubt any of this is a revelation to Scott, but I found it interesting to see actual figures attached to what we know instinctively.)

I got a dramatic seat-of-the-pants lesson in the effect a loaded roof rack can have on a trip to Mexico in my FJ40 (with its short 90-inch wheelbase and tall profile), when I rashly decided to carry an uninflated 14-foot Zodiac and a 40-horsepower Yamaha outboard up top. Total weight, including the massive Con-Ferr rack, about 600 pounds. All went reasonably well on the curvy road to Hermosillo—until I had to dodge a cow that stepped into my lane: Oh. ooh. C’mon. Jeeeez.

Back on four wheels, I thought calmly to myself, Right. Last trip with a powerboat on the roof.

Looking at the rest of Scott’s modifications, the 4.9 ring and pinion gears he installed are weaker than the stock 4.2 gears, due to the smaller pinion needed to achieve the higher ratio. Combined with the 35-inch tires this compromises the drivetrain strength. However, the second-generation Monteros came with mighty 9.5-inch rear ring gears, and substantial 8-inch gears in the front (independent) diff. So I suspect this won’t be the problem it is for those kids who stick 42-inch Mudders on Toyota pickups with 7.5-inch front diffs, then punch the locker when one wheel is spinning in thin air.

On the other side of the coin, the lower crawl ratio in the Montero is a definite asset, since it allows Scott to tackle rough sections at lower speeds, reducing the possibility of drivetrain stress, enhancing engine braking on descents, and easing transitions into off-camber situations with that higher CG. Of course high range isn’t negatively affected, so road performance remains normal—although I’d bet the combination of weight, windage, lift, and tires on Scott’s vehicle drops fuel economy of the V6 into the low teens more often than he’d like.

The last concern for Scott would be stress on the Montero’s bodywork and chassis. Again, he’s fortunate to have a strong, fully boxed ladder frame with no known weak points. The front double-wishbone and multilink rear suspension structure is sturdy and easy to modify for increased capacity. The roof rack mounting points on the drip rails might be a concern, but frequent inspection should be sufficient to detect any incipient issues.

What do the lessons from Scott Lesak’s thoughtfully outfitted, but overloaded, Montero tell the rest of us?

First, most obviously, is that if possible one should keep the all-up weight of the vehicle below the manufacturer’s GVWR. It’s easy to add a set of heavy-duty springs or air bags and then just start throwing stuff in, but just because the truck sits level doesn’t mean it isn’t dangerously overloaded. Scott showed a great deal of thoughtfulness by calculating the total weight of his Montero; how many of us have done the same, or paid five bucks at a commercial scale to see what our fully loaded overland vehicle weighs? With solid figures in hand, it’s a lot easier to decide if action is necessary to alleviate the situation.

However, rather than assembling a completely modified vehicle and camping kit, and then finding out what it all weighs, a better and less expensive strategy would be to learn from Scott’s example, and pay attention to weight from the beginning, when first modifying the vehicle and buying camping gear. 

It’s common for those starting out in the overlanding world to be tempted to get the “look” down first (I certainly was). Those winch-mounted bull bars, roof racks with six driving lights, and multi-function rear bumper/swing-outs look absolutely ace, but each one not only adds weight, it does so in the worst possible place: on the ends of the vehicle, and on top. Decide carefully whether or not you really need each. How I wish more manufacturers made sturdy winch bumpers without the bull bar, which very, very few of us really need. But apparently the market demands the full-on Aussie look . . .

Camping equipment can get out of hand easily too. Personally I think it’s odd to drive a 4,000-pound vehicle somewhere, then sleep in a five-pound mountaineering tent and cook over a microweight backpacking stove, as some friends do—but if sleeping and eating are just chores to be dealt with for you in between hikes or fishing, why carry more weight? I like to tell people to evaluate their priorities and splurge there first. For example, when car camping I like to have a tent with stand-up headroom inside, and real cots to sleep on. But I’m happy with a single-burner stove and one-pot meals. Roseann enjoys cooking, so she prefers a more comprehensive kitchen. We’ve picked and chosen to arrive at a compromise—a modest-sized but full-height tent and lightweight aluminum cots; a well-equipped kitchen mitigated by such things as a Worthington aluminum propane cylinder, which weighs half what an equivalent steel tank does. The result is a comfortable camping setup for two people (a vital distinction from Scott’s family situation). Yet, according to my calculations taking into account the known weight of our FJ60 (with M8000 winch, Slee rear bumper, and 40 gallons of diesel), with everything aboard we are just nudging past its 5,380-pound GVWR—not too bad.

When loading gear for a trip, remember that everything adds up, not just the big bulky items. Do you really need an axe, or would a hatchet or folding saw suffice? One day not long ago I finally tossed out the never-used 25-pound choker chain in our winch kit. What a difference that made. I also discovered we had somehow wound up with two folding shovels in the vehicle—not really necessary. And what on earth was that old three-D-cell Maglite still doing stuffed under the front seat? Two pounds saved . . .

If you do find yourself unavoidably abusing your vehicle’s GVWR, there are several ways to mitigate the potential side effects. First, make sure your most vital item of safety gear—the braking system—is completely up to snuff. Eschew the $49.99 lifetime brake job at the muffler shop and install the best brake pads and shoes you can find. Likewise, suspension bits should be the best available. I’ve found that, especially with shock absorbers, you really do get what you pay for. If your vehicle is equipped with anti-roll bars (a.k.a. sway bars), consider upgrading them to thicker units to reduce body roll in turns (although this will diminish compliance on trails unless you have disconnectable bars). And when on a trip, force yourself to check everything on the vehicle religiously, from the tires on up, every day—particluarly those pieces that take the most abuse from weight.

Research your vehicle to see if there are well-known weak points in its running gear or chassis. The internet has made this child’s play—you can bet if a vehicle has a common problem, word will get out. For example, a search for “Toyota Tacoma frame problems” will acquaint you with the known weakness in the rear of the frames on first-generation Tacomas. Several companies sell weld-in gussets to address the issue on this otherwise superb truck. Mid-80s Chevy trucks are notorious for numerous frame, shock-mount, and steering box weaknesses. Even Ford’s recent über-truck, the Raptor, is showing early signs of a serious chassis flaw, at least for those owners who insist on driving them like the commercials suggest. All these problems have been extensively discussed on the web.

Finally, most obviously: Pay attention to your driving, and adjust it to suit the lower capabilities of the overloaded vehicle in terms of braking performance, emergency maneuvering, side-slope security, and so on.

What would I do differently in Scott’s place? Monday-morning quarterbacking is the easiest job in the world. However, given the situation he described, I’d be very tempted to look into a 4WD-capable utility trailer from one of the growing number of companies offering them. Offsetting the hassle of a trailer would be the elimination of that 150-pound roof rack (and ladder), and the redistribution of its load, along with much more gear from the Montero’s cargo bay—which would likely mean that the 100-pound drawer system could be tossed out, along with, perhaps, the 45-pound cargo barrier. That 280 pounds of water could go in the trailer as well, as could the jerry cans which now have to reside on that 200-pound custom rear bumper and swing out. Toss that too (or go for a much lighter Hi-Lift-capable bumper with just a tire mount). With the fridge in the trailer the 50-pound fridge slide could go. We just lost over 500 pounds in one paragraph—which would, ahem, go some ways toward offsetting the weight of the trailer (although towed weight is much different from carried weight). The entire load would be distributed much more evenly (and lower), relieving the burden on the Montero. I’d be curious to see a controlled experiment regarding highway fuel economy comparing a vehicle with a high roof load to one towing a utility trailer. I strongly suspect the trailer would add more drag, but it might not be a huge difference.

On the vehicle itself, a few things jumped out at me, but again from my own perspective. The Garvin roof rack seems immensely heavy—the full-length aluminum Front Runner rack we use when necessary on our FJ60 is light enough for me to lift with one arm, yet sturdy enough to stand on. Scott’s 12,000-pound-capacity Mile Marker winch is actually well-matched to the total weight of his vehicle (gross weight x 1.5 is the general rule), but depending on frequency of use I’d be tempted to go with a Warn M8000 and synthetic line—total weight less than 80 pounds—and employ snatch blocks to increase pulling power. That would not only save weight but would remove it from the end of the vehicle, where its effects are magnified.

Scott apparently knows what he needs in the way of tires, given where he wants to go (those dual  diff locks and 43:1 crawl ratio are clues). For myself, I’ve never seen a need for tires larger than 33-inch on a vehicle that size. That would eliminate the need for the body lift, thus saving rotating weight (the worst kind) and lowering the center of gravity at the same time.

In the end, while Scott is certainly stretching the load-carrying ability of his vehicle, he could have done much worse than to choose the fine second-generation Montero as his platform. Here’s hoping it and Mark’s twin hold up for many thousands of miles of family adventuring.