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Thread: Can I tow a Grand Design?
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02-07-2018, 06:43 PM #41
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This is true. The j2807 has a combination test for the level straight line GCWR test as well as a parking test. TV brakes are designed to stop the combined load within limits but they are not designed to handle a combined load indefinitely. Not even close.
For instance, this fellows Colorado passes the j2807 test on the GCWR straight-line and parking test in addition to the Davis Dam tests. As long as he is loading within the payload and towing limits, the truck is certified to safely tow, stop and pass sway tests as the certification specifies. But it also requires he have trailer brakes based on his GVW of the trailer. I think this fellow should buy his TT and not be terrified and think he needs to invest in modifications to his truck. I do have access to all the SAE tests but due to copyright I do not think I can post them here.
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02-07-2018, 08:44 PM #42
So . . . I did find a full version of SAE J2807. Thanks Jim (Deb & Jim). BTW, SAE test procedures are copyright protected but are also public information.
To answer my own question . . . the J2807 braking tests referenced earlier are run without functioning trailer brakes even if the trailer weight requires that the trailer have its own brakes. The rationale seems to comes down to the truck manufacturer having no way of knowing the capability of the trailer brakes.
"J2807 Section 4.5.1 Combination Braking Performance Requirement Summary
The tow-vehicle brake system, in conjunction with appropriate test trailer(s) per 4.1, shall be capable of meeting certain braking requirements for the specified GCWR. The following table summarizes metrics, requirements and test methods for specific performance attributes. The purpose of 4.5 is to determine the suitability of the tow-vehicle brake system in conjunction with a trailer. Tests are to be run without the use of trailer brakes." (my bold font).
The tow vehicle and trailer combination stopping distance requirement is 80 ft from 20 MPH as referenced earlier. There is no higher speed braking test requirement in J2807. So, any tow vehicle meeting SAE J2807 is capable of stopping its GCWR without any assistance from the trailer brakes . . . at least from 20 MPH in 80 ft.
This obviously leaves a broad range of trailer braking capability that is untested and undefined. Trailer manufacturers must use some criteria in selecting the OEM brakes that they specify for different size trailers. Maybe this is a RVIA spec? I don’t know where we would go to find these.
RobCate & Rob
2015 Reflection 303RLS
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04-21-2018, 10:46 AM #43
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We are in the same boat! The 2150 looks to be a great TT for extended trips, but may be just over the edge for weight. Our Mercury Mountaineer manual says our SUV has a GCWR of 12,000 lbs and hitch rating of 500 lbs or 740lbs with a WD hitch. Allowing 5,000 lbs for the vehicle and 1,250 lbs for occupants and gear that leaves 5,750 lbs towing capacity. Not much of a margin
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04-22-2018, 07:14 AM #44
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12-25-2018, 09:04 AM #45
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Where did you find the spec? I'd like to read it. There is so much miss information that it would clear up.
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12-25-2018, 10:51 AM #46
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Here is specs
http://fifthwheelst.com/documents/to...ds-2016-02.pdf
Also 5.4 is interesting:
5.4
GVWR/Rear GAWR and Tongue Weight/Kingpin Weight Considerations
Dennis & Ellie
Current 2017 Newmar Ventana Class A & 1994 Airstream Excella Classic Limited Project
Sold - 310-GK-R Delivered 28 Oct 2016
2016 GMC Denali 1 Ton Diesel SRW Payload 3727LBS B&W Hitch
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12-26-2018, 08:20 AM #47
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Great info.....Thanks!!
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