Towing By The (Hard) Numbers
“How much can you really tow?” It’s a question that’s been a topic of debate among truck owners since time immemorial, and truth be told, there has never been an empirically verifiable way to arrive at the correct answer. At least, up to now.
Believe it or not, until 2008 there was no such thing as an industry-wide tow rating standard—only a bunch of suspect claims and counter-claims from the individual manufacturers, based on test procedures of their own making, and generally devised to place their own vehicles in the most flattering light. This helps to explain why tow ratings for pickup trucks seem to change as often as most of us change our socks, and how the ratings of ½-ton pickup trucks have climbed to stratospheric levels that were once the sole province of heavy-duty rigs. Can that six-lug pickup truck really tow 9,500 pounds without blowing out the rear diff and cooking the tranny? Well, up to now, we’ve simply had to take each manufacturer’s word for it.
Fortunately, that’s all about to change.
Starting in model year 2013, all trucks will conform to a uniform SAE test standard to determine maximum trailer weight ratings. Known as Surface Vehicle Recommended Practice J2807, the new standard will employ a variety of repeatable test methodologies which mandate things like identical trailer frontal areas, axle-load distribution weights and trailer tongue weights among like vehicles. You mean this kind of practice wasn’t followed before? Not necessarily.
Among the specifications spelled out in the new SAE protocols:
Acceleration: New trucks will have to meet minimum acceleration times pulling a given trailer weight from zero to 30, zero to 60, and 40 to 60 mph to claim that weight rating. The time standards differ between single- and dual-rear wheel applications.
Braking: Same thing, basically, only with maximum stopping distances mandated according to trailer weight. The longest allowable stopping distance for any rig is 80 feet from 20 mph (trailers over 3,000) with no trailer brakes. The e-brake must be able to hold the rig on a 12-percent grade (in both directions, uphill or down), and structural standards are imposed for the hitch assembly, with no more than 5 degrees of angular deflection allowed.
Highway performance: All tests will be conducted on the same 12-mile road loop in the Nevada/Arizona desert in 100-degree (or hotter) weather, with the A/C and blower in the tow rig both set on maximum (no recirc). The loop has an average road grade of 5 degrees, and the test vehicle must come with the tallest available axle gears. No coolant loss is allowed, and the tow vehicle can’t start throwing error codes or tripping idiot lights during the test loop. (We’re thinking this is even better than the Tow Test at Top Truck Challenge.)
Road handling: Required levels of understeer are mandated for vehicles towing with or without a weight-distributing hitch.
Grade launching: From a stop, the tow vehicle and trailer need to be able to move 16 feet on a 12-percent grade, both in Drive and Reverse gears, five times each way in five minutes.
If you’re like us, you can only be amazed that these sorts of protocols weren’t already in place. But thankfully, now they are; the OE manufacturers have embraced the new requirements, and one manufacturer—Toyota—has already tow-rated its pickup-truck line based on the test requirements of SVRP J2807. For those of you who tow regularly—and judging by our reader surveys, that’s more than half of you—this is positive news indeed. Knowledge is empowering, after all, and for all of us with tow rigs who’ve ever struggled with overheated engines or blown axle seals, we’ve already found out the hard way that when it comes to hauling heavy loads, what we don’t know can hurt us.