SAE Cargo Volume and Towing Standards - Whale Watching
Trust But Verify
Last year’s debates about what a truck really weighs and can carry made a strong case for detailed standards being more important than doing it the way everybody else does. It reminded us that, although the Society of Automotive Engineers (SAE) had finalized J2807 for trailer towing, there was still some room for Smokey Yunick-style creative thinking.
This came back to haunt me recently when I was checking comparative data on two-row crossover cargo area, knowing that SAE had developed trunk or cargo area measurement formulae half a century ago. I ran across one that listed cargo volume behind the second row as based on SAE’s J1100 standard, but behind the first row, two values were listed, one for SAE J1100 and a 25 percent larger number. The footnote read, “SAE H1100 cargo volume measurement standard plus floor space between first and second seats and front seats moved forward. This figure compares more accurately with most competitive measurements.”
Crap. Now to cite any comparative numbers I had to figure out what standard, if any, the manufacturers were employing for this and if the numbers applied if the driver is more than 5 foot, 2 inches tall.
I knew some manufacturer volumes included bins under the cargo floor and that sedans and hatchbacks can’t be compared (hatches include space to the roof), but why the variance according to J1100? Two big reasons: One, it’s not a binding legal document, leaving plenty of room for manufacturer interpretation, and two, because there have been at least ten updates from its genesis.
So I asked companies that make vans and SUVs for North America which standard they used and received as myriad answers as non-replies. Most said J1100 with a few specifying which version to answer the question, including 1975, 2002, 2009 and 2011 revisions, some included VDA (German) and ISO standards, while another noted they’d had so many recent requests for the info it simply wouldn’t be available by deadline. Hmmm.
At least it explained some things, like why quoted volume was bigger but space looked smaller. Some things I don’t mind putting on the floor, but squishing the dog under a folded seat and me up against the windshield? No.
I’m thinking any apples-to-apples comparison would involve me procuring a batch of balls 6 to 12 inches in diameter, inflating them to an NFL-approved-and-verified pressure, and counting how many I could stuff in—below the cargo cover, with it removed and including under-floor compartments designed to hold cargo, not carpet mats. I could even put some behind the seat in a regular-cab pickup since it wouldn’t be much of a manly-man truck with just two balls, would it?
We’ve known for years that power ratings are often pessimistic, so they can be bumped 10 hp or 20 lb-ft in next year’s marketing with no actual changes. Engine sizes with historical relevance get used despite being inaccurate—Chrysler’s recent 392 that’s really a 391, Mercedes’ more egregious 6.3 that was really a 6.2 (of less displacement than GM’s 6.2), and current AMG 63 models, most of which have 5.5 liters of displacement.
Conversely, “four-wheel drive” now gets used as it did originally, for four driven wheel hubs (don’t want to leave out dually owners). I’ve always applied “four-wheel-drive” to vehicles with shiftable low-range transfer cases and “all-wheel drive” to those that don’t. Twenty-five years ago I tested a trio of vans (GM Astro, Ford Aerostar, Toyota Previa) that offered all-wheel drive, under the subtitle “the SUV alternative.” Now most vehicles with four driven wheels use a system closer to those vans than any two-speed transfer case. Even stalwarts like many Land Rovers and Jeeps no longer come with low range standard.
Maybe they don’t need to. An old 2.48:1 first and 2:1 low-range delivered similar gearing to driveshafts as a new 4.71:1 first and 1:1 high. Of course, the old low-range worked for reverse as well, the trucks were lighter, the tires smaller diameter and differential gears often shorter. Either way, a numerical gear ratio doesn’t require a standard.
I’ve always been a pessimist and questioned authority. Now the term “SAE standard” doesn’t mean as much to me (all due respect to that fine organization). I’m eagerly awaiting the asterisk or footnote that says ground clearance is with the tires inflated to full load and the truck empty (at its “curb” weight), the breakover value published is with the side steps removed, the departure angle that doesn’t include the optional trailer hitch, and angle of approach that applies only after the air dam has been “easily removed with hand tools.” Because, you know, those hand tools are already in the truck, right next to the jack and spare tire.