Subaru Outback Forums banner

1 - 19 of 19 Posts

·
Registered
2005 OBW 2.5L, 1989 Subaru Justy, RIP Blu
Joined
·
7,355 Posts
Discussion Starter #1
Preposterous as it may seem, until recently there was no legitimate means of comparing the trailer-tow rating advertised by one truck manufacturer with claims issued by competitors. That created a game of leap-frog. With the introduction of every new large truck, the proud manufacturer would announce some new high in the number of pounds that could be hauled or towed. That would prompt one or more competitors to pause for a few months before announcing revised tow ratings for their products which would of course return their progeny to the top of the towing heap.
But after years of effort, the SAE's tow vehicle trailer rating committee is finally ending the farce. The SAE's Surface Vehicle Recommended Practice J2807 spells out in precise terms a procedure for determining two important ratings: the maximum permissible gross combination weight (GCWR) for a tow vehicle and its trailer and the maximum permissible trailer weight rating (TWR).
After three years of effort by the three domestic manufacturers and representatives from several of the Japanese brands, a standard was approved in April 2008 and scheduled for 2013 model year implementation. Some companies have already begin phasing in the more realistic J2807 tow ratings for their new models.
There are five engineering characteristics that strongly influence any tow vehicle's performance:
The engine's power and torque characteristics.
The powertrain's cooling capacity.
The durability of the powertrain and chassis.
Handling characteristics during cornering and braking
maneuvers.
The structural characteristics of the vehicle's hitch attachment area.
Standard J2807 spells out test procedures and performance requirements that must be meant for a manufacturer to assign a maximum tow rating to a particular vehicle. While various trailer configurations are suitable for these tests, the towed unit must provide a minimum specified frontal area starting with 12 square feet for a TWR below 1500 pounds, ranging to 60 square feet for a TWR exceeding 12,000 pounds. There are also specifications for how the trailer's load is distributed on its axle(s) and how the attachment tongue is configured.
One major change from past practice is what the SAE committee defines as Tow Vehicle Trailering Weight (TVTW). Unlike the past, a driver, a passenger, optional equipment purchased by at least one third of the customer base, and hitch equipment are now included in this calculation along with the base weight of the tow vehicle. Raising the TVTW figure automatically lowers the maximum permissible GCWR and TWR figures.
Acceleration Performance Requirements
The tow vehicle must meet these level road performance criteria to merit a particular TWR:
Acceleration from zero to 30 mph in 12.0 seconds or less in vehicles with a single rear wheels.
Acceleration from zero to 30 mph in 14.0 seconds or less in vehicles with dual rear wheels.
Acceleration from zero to 30 mph in 16.0 seconds or less in vehicles with dual rear wheels and a GVWR over 13,000 pounds.
Acceleration from zero to 60 mph in 30.0 seconds or less in vehicles with single rear wheels.
Acceleration from zero to 60 mph in 35.0 seconds or less in vehicles with dual rear wheels.
Acceleration from zero to 60 mph in 40.0 seconds or less in vehicles with dual rear wheels and a GVWR over 13,000 pounds.
Forty to 60 mph passing acceleration in 18.0 seconds or less in vehicles with single rear wheels.
Forty to 60 mph passing acceleration in 21.0 seconds or less in vehicles with dual rear wheels.
Forty to 60 mph passing acceleration in 24.0 seconds or less in vehicles with dual rear wheels and a GVWR over 13,000 pounds.
Grade Launch Requirements
The tow vehicle must be capable of repeatedly moving from rest for a distance of 16 feet on a 12-percent grade in both forward and reverse directions. Five such launches must be accomplished within five minutes in each direction.
Highway Gradeability
To merit a particular TWR, a vehicle must be capable of maintaining a minimum cruising speed while climbing the grade at Davis Dam on state roads 68 and 163 in Arizona and Nevada. This 12-mile-long run originating in Bullhead City, Arizona, involves grades that vary between 3- and 7-percent with an average over 5-percent. During this test, the minimum acceptable ambient temperature is 100-degrees F. and AC systems must be operating on the maximum cold setting with no recirculation and the blower at the highest possible setting.
Single rear wheel vehicles must be able to maintain an average of at least 40 mph on this grade. Dual rear wheel vehicles are required to maintain 35 mph or more here. Dual rear wheel vehicles with a GVWR over 13,000 pounds must maintain at least 30 mph.
To pass these hot-ambient-temperature, steep-grade challenges, there can be no vehicle component failures, no warning lamps, and no diagnostic codes alerting the driver. In addition, the tow vehicle cannot lose any engine coolant. The vehicle under test must be equipped with the lowest numerical axle ratio available from the manufacturer.
Handling Requirements
Standard J2807 specifies that an understeering handling attitude must be maintained up to at least 0.4g cornering without a weight distributing hitch. With a weight distributing hitch (which transfers vertical load from the tow vehicle's rear wheels to its front wheels), an understeering attitude must be maintained up to only 0.3g cornering.
Braking Requirements
The test vehicle and trailer must stay within a 11.5-foot wide traffic lane during stopping tests. The parking brake must be capable of holding the rig on 12-percent up and down grades.
Stopping distance requirements from an initial 20 mph without use of trailer brakes are:
In 35 feet or less with a TWR of 3000 pounds or less and no trailer brake requirement.
In 45 feet or less with a TWR of 3000 pounds or less and a trailer brake requirement.
In 80 feet or less for TWRs above 3000 pounds.
To assure that the tow vehicle's structure is capable of towing a particular trailer load, standard J2807 specifies that no more than 5 degrees of permanent angular deformation at hitch attachment points is acceptable. Also, the highest experienced trailer hitch attachment force must be withstood for five seconds without significant loss of load (no structural deflection).
The SAE towing committee purposely defined the scope of this standard not to include brake fade and durability aspects related to the tow vehicle such as the endurance of chassis, powertrain, suspension, and brake components. Other SAE standards and each manufacturer's own internal requirements instead address these towing issues.
If all requirements specified in J2807 are met, the tow vehicle manufacturer may state the following: This model meets or exceeds the tow-vehicle trailering requirements of SAE International per SAE J2807. All manufacturers are strongly encouraged to use this test for tow ratings beginning with the 2013 model year. Some brands that have tired of the leap-frog game -- Toyota for one -- have already commenced use of this worthwhile trailer towing advancement.


Read more: Tow Ratings Finally Pass the Sniff Test - The Society of Automotive Engineers (SAE) - Automobile Magazine
 

·
Registered
2013 2.5i Premium 6mt, Twilight Blue
Joined
·
2,378 Posts
Interesting. I have no experience with towing or tow ratings; do the cliffs of this standard mean that a manufacturer will load up a trailer/tow vehicle to a certain weight, and as long as it passes all the tests above it will be approved as capable of towing that weight?
 

·
Registered
'14 3.6R Outback
Joined
·
2,345 Posts
Wow. That is some crazy requirements. I'm not saying their bad, but man no wonder towing numbers have dropped. They basic just needed to say when you tow we prefer the car drives like there is barely anything there.
 

·
Registered
2012 Outback 2.5i CVT
Joined
·
468 Posts
Everything here looks great to me except one thing. Why do they allow permanent hitch deformation of any kind? I would think allowing elastic deformation would be the correct measure as working in the plastic region of a material isn't usually smart for continuous loading. Everything else is probably conservative but it's nice to know what you can do safely in my book.
 

·
Registered
Joined
·
22,836 Posts
Given this standard was created in 2008 and goes into effect 2013 Subaru has been aware of it for some time. My guess is that either Subaru is already more or less building the cars and rating them based on this standard or we will see what many of us who have been towing for some time with various Subarus know all quite well - is that for any sort of long distance hauls with hot temps and climbs the Weight limit really is much lower than the 2700lb limit - and given Subaru even lists heat related limitations in the owners manual this might be the loop hole Subaru is using to list its towing capacities given the heat related limitations is

5 mile climb 5+% grade in 104 Degrees is used for the CVT and 5spd EAT to show a 1350lb and 1500lb limit. But Subaru lists 2700lbs as its towing maximum under ideal conditions - flat cool temps etc. So very possible Subaru will keep its rating more or less the same with the owners manual stating conditions vs limits that apply to each version of the vehicle.
 

·
Registered
2008 Outback 2.5i
Joined
·
1,148 Posts
The SAE J2807 is voluntary though. So you now you have to check with the manufacture that the TV complies with J2807.
 

·
Registered
2014 OBW 3.6R Limited, 1997 OBW 2.5L Auto (sold, but not forgotten), and 1991 Ford F150
Joined
·
1,525 Posts
Pickup truck manufacturers always seem to be one upping each other on their advertised tow ratings, so it will interesting to see if they will fully comply with the new standard given that their tow ratings will almost certainly come down substantially. I also wonder if manufacturers can cherry pick their models, i.e. the ratings of some models in their lineup will comply and others will not.

One of my favorite quotes from my days in IT: Standards are wonderful things because there are so many to choose from.
 

·
Registered
2012 Outback 2.5i CVT
Joined
·
468 Posts
Pickup truck manufacturers always seem to be one upping each other on their advertised tow ratings, so it will interesting to see if they will fully comply with the new standard given that their tow ratings will almost certainly come down substantially. I also wonder if manufacturers can cherry pick their models, i.e. the ratings of some models in their lineup will comply and others will not.

One of my favorite quotes from my days in IT: Standards are wonderful things because there are so many to choose from.
Yeah but if GM were to use this new standard, which they are along with at least Toyota from my knowledge, and someone like Ford were to not use it that would be great for GM as well. Now all the Chevy commercials would point out that Ford's tow ratings are worthless and when you buy a Chevy there's no question what you are getting... or something like that. Blue collar truck guys don't like fake, unsubstantiated numbers. Even Motor Trend and the other mags are point out and testing trucks to this SAE standard so the truth would come out too quick. I bet all the big truck companies use the standard, it's non-trucks like the Outback that will want to stay away from it.
 

·
Registered
2010 2.5i Outback, 2015 2.5i Legacy w/Eyesight
Joined
·
595 Posts
Wow. That is some crazy requirements. I'm not saying their bad, but man no wonder towing numbers have dropped. They basic just needed to say when you tow we prefer the car drives like there is barely anything there.
I wonder what this means for companies like U-haul. U-haul seems to allow trailer rental based on the vehicle's tow rating from the manufacturer to keep from being sued. If the allowed tow rating drops to almost nothing for even a short trip on level pavement now, that will cut out a lot of options for the occasional towers and hurt their trailer business.
 

·
Registered
Joined
·
22,836 Posts
I wonder what this means for companies like U-haul. U-haul seems to allow trailer rental based on the vehicle's tow rating from the manufacturer to keep from being sued. If the allowed tow rating drops to almost nothing for even a short trip on level pavement now, that will cut out a lot of options for the occasional towers and hurt their trailer business.
Not really - given very few people who rent Uhaul trailers are driving cars. Not to mention most people who do try to rent a trailer far far too large for their tow vehicle should probably never be rented a trailer to start with.

My dad taught drivers ED for 24yrs to help supplement his teachers pay. He always told the kids if you need to know what cars to avoid? Avoid the rental trucks and trailers given its a very safe guess the driver has zero experience driving such a large vehicle or towing the trailer.
 

·
Registered
'11 Outback 2.5i CVT - '06 Forester X 5MT
Joined
·
1,766 Posts
I doubt any "non towing" vehicle will bother to comply. That's a lot of testing for an OB or similar vehicle that, truly, isn't built for towing. They'll just stick to their already conservative numbers and leave it at that.

Now the big boys that are bragging about towing abilities will probably all comply, because otherwise any manufacturer with a PR team worth a squat, will exploit that.

But it's good to see that there is a standard that can be referenced.
 

·
Registered
2012 Outback 2.5i CVT
Joined
·
468 Posts
I wonder what this means for companies like U-haul. U-haul seems to allow trailer rental based on the vehicle's tow rating from the manufacturer to keep from being sued. If the allowed tow rating drops to almost nothing for even a short trip on level pavement now, that will cut out a lot of options for the occasional towers and hurt their trailer business.
You would think that's how Uhaul determines what a vehicle can tow, that's what I thought. I used to have a '95 S10 pickup and wanted to rent a 6x12 Uhaul trailer. That trailer has a maximum GVWR of 4,400 lbs and my truck was rated by Chevy to tow 5,000. Uhaul refused to rent me the trailer because in their books my truck was not permitted to tow the 6x12. I emailed Uhaul corporate and got the reason why right from them and in an actual email instead of verbal. Their tow ratings are determined by tow vehicle empty weight and not manufacturer's tow rating. If I had the extended cab model Uhaul would let me tow the 6x12 because my truck weighed more, though all suspension, drive train, and brake components were identical. This is why you often see front wheel drive minivans towing big Uhaul trailers that are too large for the vehicle. Now this was probably 10 years back when I emailed them so maybe things are different today. Uhaul has never been an example of safety and good practices. Anyone remember how they hooked up trailers back in the 70's. Uhaul would just clamp a hitch to the steel bumper and off you went with a trailer.
bumper_hitch_detail.jpg
 

·
Registered
2008 Outback 2.5i
Joined
·
1,148 Posts
Think again. Both Ford and GM are not using the voluntary standard. Yet the Toyota Highlander is using the standard. WTF.
 

·
Registered
2010 2.5i Outback, 2015 2.5i Legacy w/Eyesight
Joined
·
595 Posts
Not really - given very few people who rent Uhaul trailers are driving cars. Not to mention most people who do try to rent a trailer far far too large for their tow vehicle should probably never be rented a trailer to start with.
Not that anyone who likes a working transmission would regularly test the limits, but do you think your 4-cylinder CVT easily meets the "Acceleration from zero to 60 mph in 30.0 seconds or less in vehicles with single rear wheels." requirement while towing your boat?

If not, then you would probably be in the new category of people trying to rent a trailer "far far too large for their tow vehicle" if you tried to rent a trailer of similar load under from a trailer renter that followed the new requirements, no?

Most of the vehicles I see driving U-haul trailers are cross-over vehicles and I would think it would impact those vehicles (and therefore Uhaul's business to at least a noticeable extent if they followed the new towing measurements). But, vtmecheng's point makes this discussion moot.

I emailed Uhaul corporate and got the reason why right from them and in an actual email instead of verbal. Their tow ratings are determined by tow vehicle empty weight and not manufacturer's tow rating. ... Uhaul has never been an example of safety and good practices.
Thank you for that information. From that standpoint, this will not impact Uhaul business a bit and it makes sense to some degree that they came up with their own standard of measurement over the years given the lack of a standard (be it overly-simplistic and not much good since it's a bad measure and they assume partial liability rather than pushing the liability to the manufacturer by citing the manufacturers' recommendations).
 

·
Registered
Joined
·
22,836 Posts
Not that anyone who likes a working transmission would regularly test the limits, but do you think your 4-cylinder CVT easily meets the "Acceleration from zero to 60 mph in 30.0 seconds or less in vehicles with single rear wheels." requirement while towing your boat?

If not, then you would probably be in the new category of people trying to rent a trailer "far far too large for their tow vehicle" if you tried to rent a trailer of similar load under from a trailer renter that followed the new requirements, no?

Most of the vehicles I see driving U-haul trailers are cross-over vehicles and I would think it would impact those vehicles (and therefore Uhaul's business to at least a noticeable extent if they followed the new towing measurements). But, vtmecheng's point makes this discussion moot.
Would the 2.5 cvt do the speed vs time test with the 21ft 1700lb boat in tow? Easily will it do that on a 8+% grade - no. 5% grade? Maybe but I wouldn't be pushing the car as hard as it would run on a 5% grade either unless it was a very short one like say a freeway on ramp. ;-)

"Acceleration from zero to 30 mph in 12.0 seconds or less in vehicles with a single rear wheels."

The 40 to 60 mph test for passing would be illegal requirement in my state where your max trailer speed is 55mph and they are quite strict about it. A speeding ticket with a trailer in my state is basically 3x the standard speeding fine you would get without the trailer. Will the 2.5 with CVT do this though? Sure it hauls along nicely at 65-70mph and will pick up from 40-50 to 60-70mph nicely on fairly standard flat ground hauling.

Would the 2.5 go from 40 to 60mph in 18 seconds? Flat towing easily - 5% grade might be cutting it very close if not at all given again 5% grade for more than a very short distance when towing a trailer like that you don't hammer the tow vehicle if you expect to see any sort of longevity or extended reliability out of the vehicle to start with.
 

·
Registered
2012 Outback 2.5i CVT
Joined
·
468 Posts
Think again. Both Ford and GM are not using the voluntary standard. Yet the Toyota Highlander is using the standard. WTF.
Yeah, I read in another article that GM was supposed to start using the standard and even published the numbers for a short time before retracting them. Guess they decided it wouldn't look good to have lower tow numbers than competitors even if the numbers don't actually mean anything. The Highlander uses the standard because Toyota decided to adopt them early.
 
1 - 19 of 19 Posts
Top