RP gets away with exceeding the Subaru limits by understanding what the conditions for the SAE recommended ratings for his Crosstrek are.
He takes it easy on a mostly level road on a short duration trip.
The Subaru ratings have to include a worst-case-scenario of a steep, long, hot run with several stops and starts in both forward and reverse.
I.E. New SAE Standards
The upcoming SAE J2807 recommended practices will include five areas of testing: structure, propulsion, thermal, handling, and braking. The structure tests validate body, bumper, and frame strength and the hitch itself. The propulsion tests include: launching five times in five minutes, in forward and reverse, on a (very steep) 12-percent grade; zero to 30, zero-to-60, and 40-60-mph level-road acceleration tests;and minimum speed on the Davis Dam grade.
The thermal test, which is part of the long, grueling Davis Dam gradeability exercise, requires no loss of fluids and no warning alerts that would require customer action--and it must be done at 100 degrees F or hotter. The handling tests require sufficient trailer-sway damping and stability enhancing tow vehicle understeer with weight-carrying and weight-distributing hitch setups. The brake tests specify a maximum stopping distance from 20 mph (from federal regulations) and both uphill and downhill park-brake performance on a 12-percent grade.
"SAE J2807 will say, 'Here are your performance requirements to set a GCWR--how fast you can get up a hill, how cool the truck is while doing it, how well the combination handles, etc.,'" says GM's Krouse. "Then the last section says, 'Now that you have validated to this GCWR, here's how to calculate your trailer weight rating from it.'
"And we're not going to let people use a stripped-down model to get their ratings for a whole group of models. We require the whole EPA content, the same weight we use for fuel economy and emissions certification, including two people. It will also take into account representative aftermarket trailering equipment--hitch inserts, weight-distributing bars if needed, and so on. We're trying to do it the way people really buy and use these vehicles, and anything that has a tow rating should follow these practices.
Even a Chevy Cobalt that wants to tow a 1000-pound trailer has to accelerate on grades, have cooling to get up those grades, and be able to handle and stop that trailer."
Haha, I grew up on a farm in Manitoba. We did a lot of towing of all kinds of stuff when I was a kid... We had a few hills where we lived, and I learned early on, going up a hill was a lot easier/safer than going down...
Really interesting to see the safety metrics taken into account in the standard, thanks for the info. Then again, a standard is just that - an umbrella regulation designed to cover (nearly) )all the worse-case possibilities and solve liability issues. Folks who want/need to haul something large on a flat road over 50 km might, in all likelihood, exceed the rating with no issues whatsoever, gently slowing and accelerating as they see fit. Try an emergency stop a long downhill stretch from 75mph, or climbing a steep grade at 4000 m ASL with traffic behind you, and you might appreciate the official rating limits.