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Old 01-06-2019, 01:54 PM   #29
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Is this SAE J2807 test really what is used now to determine towing limits? Seam kinda weak for a spec. Has anything really changed since it was introduced?
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Old 01-09-2019, 12:08 AM   #30
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Apparently not since the thread has been dead for 3 years.

Spcifications to protect us from misleading advertising are right up there with “do not attempt” wording on commercials.
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Old 01-09-2019, 04:44 PM   #31
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Is this SAE J2807 test really what is used now to determine towing limits? Seam kinda weak for a spec. Has anything really changed since it was introduced?
I was going to respond, but then went back and read the thread from the beginning, and found my previous responses. My thoughts posted there havenít changed. And I donít think anything has changed in the market apart from some advertising copy.
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Old 01-11-2019, 01:15 PM   #32
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I was going to respond, but then went back and read the thread from the beginning, and found my previous responses. My thoughts posted there havenít changed. And I donít think anything has changed in the market apart from some advertising copy.
Thanks for the update. The more I think about this spec, the more it seems a marketing ploy than a true specification. There is so much wiggle room in it that any good engineer can modify the vehicle to pass the "hardest part" of each test. I won't hold my breath for them to tighten the spec any time soon.
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Old 01-11-2019, 01:35 PM   #33
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Thanks for the update. The more I think about this spec, the more it seems a marketing ploy than a true specification. There is so much wiggle room in it that any good engineer can modify the vehicle to pass the "hardest part" of each test. I won't hold my breath for them to tighten the spec any time soon.
I wouldn't expect the standard to be tightened. It is a truth in advertising standard, not a safety standard. Just like the SAE hp spec, it means than when you measure it you are doing it under standard conditions. It doesn't say how much hp you may want or need, just that one hp measurement can be compared to another. And even with that example, there are ways around it. BMW famously announced that their twin turbo made 300 flywheel hp some years back. Then people found the vehicles were quicker in acceleration than they should be, and put the vehicles involved on the dyno and found that they were getting more than 300 hp at the rear wheels, despite all the drivetrain losses (which can't be negative). People asked BMW why they used 300 hp as the rating. No comment. It wasn't against the rules. But if they had claimed more than the dyno measured, they couldn't have done that without violating the standard. Nothing stopped them from underrating them.
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Old 01-11-2019, 08:51 PM   #34
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We enjoy living here in Colorado. Traversing mountain passes at 12,000 feet is part of the lifestyle. I often see folks lugging their big fifth wheels up and over a high pass. I often see folks by the side of the road with the hood up waiting for things to cool down. I often pass tow vehicles and trailers making just 30 mph going up some long and steep 7% grades. And the downhill side of the pass is a real test of the braking capability of the vehicles.

So this towing test standard is a way for manufacturers to verify their claims of towing capability. If my pickup is rated to tow a conventional trailer weighing 12,000 pounds, I would expect it not to overheat, or significantly speed droop, or experience brake fade while towing that weight here in Colorado.

What marketing says the engineers must verify with real world data.

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Old 01-12-2019, 01:23 AM   #35
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We enjoy living here in Colorado. Traversing mountain passes at 12,000 feet is part of the lifestyle. I often see folks lugging their big fifth wheels up and over a high pass. I often see folks by the side of the road with the hood up waiting for things to cool down. I often pass tow vehicles and trailers making just 30 mph going up some long and steep 7% grades. And the downhill side of the pass is a real test of the braking capability of the vehicles.

So this towing test standard is a way for manufacturers to verify their claims of towing capability. If my pickup is rated to tow a conventional trailer weighing 12,000 pounds, I would expect it not to overheat, or significantly speed droop, or experience brake fade while towing that weight here in Colorado.

What marketing says the engineers must verify with real world data.

David
Not sure how real world that test is.

I am not aware of any fifth wheel trailers that have the minimal frontal area of the J2807 standard, it is spec'd at even less than an Airstream.

The test is only at 40 mph, 35 mph for DRW vehicles, so not far off what you have seen.

The braking test is on flat ground, not a descent, doesn't use the trailer brakes, and is from only 20 mph. I would be surprised if that brought up issues of brake fade which may exist on the roads you reference. It would be relevant to a stop in a typical parking lot.

Just doesn't seem very real world.
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