Confused about calculating GCWR - Escape Trailer Owners Community

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Old 12-27-2013, 03:14 PM   #1
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Confused about calculating GCWR

Hi, thought I had this all sorted, but confusion is creeping in as I read some posts.

I get the impression that some add the tongue weight to the trailer to calculate total trailer weight. Then use this total trailer weight in calculating weight limits.

But the tongue weight is added to the tow vehicle payload calculations, so it seems like it would be double counting to also add tongue weight back to the trailer?

Anyone help me out on this? Thanks. j
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Old 12-27-2013, 03:22 PM   #2
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The gross combination weight rating (also Gross Combination Mass and maximum authorised mass), which can be abbreviated to GCM, MAM, GCWR is the maximum allowable combined mass of a towing road vehicle, passengers and cargo in the tow vehicle, plus the mass of the trailer and cargo in the trailer.This rating is set by the vehicle manufacturer.
The GCWR is a function of the torque output of the engine, the capacity and ratios of the transmission, the capacity of the driving axles and tires, the capacity of the radiator, and the ability of the chassis to withstand that powertrain torque.
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Old 12-27-2013, 03:31 PM   #3
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I realized after posting that my title included the "R" for rating..... I am thinking about calculating actual combined weight.... j
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Old 12-27-2013, 05:48 PM   #4
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Quote:
Originally Posted by jamie beers View Post
I get the impression that some add the tongue weight to the trailer to calculate total trailer weight...

But the tongue weight is added to the tow vehicle payload calculations, so it seems like it would be double counting to also add tongue weight back to the trailer?
The tongue weight is included - just once - in each weight category where it applies.

For instance:
Total trailer = trailer axle + trailer tongue
Gross vehicle = empty vehicle + passengers + cargo + trailer tongue
Gross combined = empty vehicle + passengers + cargo + trailer axle + trailer tongue
or
Gross combined = empty vehicle + passengers + cargo + trailer total (no need to add the trailer tongue again since it is already in the trailer total)
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Old 12-27-2013, 06:25 PM   #5
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Quote:
Originally Posted by Brian B-P View Post
The tongue weight is included - just once - in each weight category where it applies.

For instance:
Total trailer = trailer axle + trailer tongue
Gross vehicle = empty vehicle + passengers + cargo + trailer tongue
Gross combined = empty vehicle + passengers + cargo + trailer axle + trailer tongue
or
Gross combined = empty vehicle + passengers + cargo + trailer total (no need to add the trailer tongue again since it is already in the trailer total)
Ok, thanks, that's what I thought. Got confused reading some other posts today. j
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Old 05-23-2016, 01:52 PM   #6
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The Province of Alberta has a simple pdf sheet called "Recreational Vehicle Towing Guide" that explains GCWR & CVWR. It can be found at:
http://www.transportation.alberta.ca...ehtowguide.pdf
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Old 05-23-2016, 02:21 PM   #7
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To put in layman terms, added to the tow vehicle because you are carrying it plus added to the axle weight because you are pulling it......
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Old 05-23-2016, 04:37 PM   #8
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Originally Posted by ve7ztw View Post
The Province of Alberta has a simple pdf sheet called "Recreational Vehicle Towing Guide" that explains GCWR & CVWR. It can be found at:
http://www.transportation.alberta.ca...ehtowguide.pdf
I think the cover is classic Alberta: every vehicle shown is a truck, and they even show a trailer pulled behind a fifth-wheel trailer.

On the recent theme of typos: one section title is actually "BREAKING REQUIREMENTS FOR TRAILERS". Gee, I didn't know the government requires us to break our trailers. Brakes, on the other hand, are good.

This is actually wrong in a couple of ways:
Quote:
Gross Combination Weight Rating (GCWR)”; the GCWR, sometimes expressed as the maximum trailer towing capacity, may change with different engine, transmission, and differential combinations, and is normally found in the owner's manual. The GCWR is the maximum weight of the truck and trailer combined. The maximum trailer towing capacity is the maximum weight of a trailer which may be towed when your truck is empty (no payload), any load carried in the truck will reduce its maximum trailer towing capacity.
  1. GCWR is the allowed total of tug (whether or not it is a truck) and trailer with their loads, but is obviously not the same as the "maximum trailer towing capacity".
  2. GCWR limits the maximum trailer towing capacity, but it is not the only limit, so if another factor caused the manufacturer to set a lower trailer weight limit, it may not correspond to an empty tow vehicle. My Sienna can have almost half a ton of people and cargo in it while towing the maximum rated trailer weight without violating GCWR; it would probably have a higher trailer weight limit if Toyota was willing to allow higher hitch weight.

Another small issue:
Quote:
The front and rear GAWR’s added together will always be greater than the GVWR
The total of the GAWRs will always be greater than or equal to the GVWR.

The guide is actually pretty good, with lots of useful information - it just appears to have been assembled by someone who doesn't really understand it.
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Old 05-23-2016, 08:32 PM   #9
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Always hated calculus
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Old 05-23-2016, 09:26 PM   #10
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Originally Posted by bsmoke View Post
Always hated calculus
Good thing this is only algebra!
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