Monday, October 5, 2015

Understanding Weights

Thanks to Mike Fultz and my DW for information they contributed for this article.

One of the most important things to understand about the RV is its weight - and how much weight it can carry.  I have been particularly concerned with this issue, because Newmar added a lot of weight to the 2016 version of the standard coach that I'm ordering so that they could accommodate tile in the slides and a sturdier frame.

The weight limitations for an RV are mostly determined by the manufacturer of the chassis.  When reading all of the terms and abbreviations, it may help you if you consider that:
  • "Rating" means "Maximum" and 
  • "Gross" means "Total"
So GVWR (Gross Vehicle Weight Rating) can be thought of as Total Vehicle Weight, Maximum - or the maximum total weight of the vehicle.

Remember that it's important to weigh the RV after you've loaded it, paying special attention to the weight on each axle.  Weight distribution is important!  It's especially important to watch the weight on the front axle.  You don't want to overload any axle, but should be particularly careful about the one in front.  Do everything you can to move weight off the front and towards the rear so the other axles can pick up a higher (percentage) share of the load.

These are things that they can tell you about a particular model before they actually build it.  They represent the maximum weights that can be supported by the chassis:
  • Gross Axle Weight Rating (GAWR).  This is the maximum weight that a particular axle can support.  Each axle has its own GAWR. 
  • Gross Vehicle Weight Rating (GVWR).  This is the most that the coach can weigh.  It is often the total of how much all of the axles can support, so it's equal to (or close) to the sum of all of the GAWRs.  
  • Gross Combined Weight Rating (GCWR).  This is the GVWR plus the weight of anything else you add or pull behind it.  Don't confuse this with the hitch rating, which is how much weight the hitch assembly can pull.  If you have a motorhome with a GVWR of 40,000# and are going to pull a truck that weighs 5,000#, you need to make sure that your GCWR is 45,000# or higher.  If you take the GCWR and subtract the GVWR, you'll see how much weight you can pull - as long as your hitch is also rated to pull the weight.  You may find when you calculate how much you can pull that you can pull 10,000# and still be under the GCWR.  However, your hitch may only be rated for 5,000#.  Be sure everything lines up.
The things below are actual measurements for your specific one-of-a-kind RV.  After it's built and options have been added, they put a sticker in the unit that gives you the real numbers.  Note that the manufacturer will usually publish some of these as approximate numbers for your model type, but until the coach actually exists and they weigh everything, you won't have the real deal.
  • Unloaded Vehicle Weight (UVW).  Notice that it doesn't say "Rating", so this is an actual measurement of a particular motorhome's total weight when they drive it out of the factory with FULL fuel tanks, oil and coolant.  Nothing else is included in the UVW.
  • Net Carrying Capacity (NCC).  This is obtained by subtracting UVW from the GVWR.  What's left after the subtraction is the weight of anything you put into the coach other than fuel, oil and coolant:  occupants, fresh water, clothes, LP gas, dealer-installed accessories, dishes, and any other cargo you put in the coach.  If you add up the weight of these things, it should not exceed the NCC.  Note that manufacturers and many in the RV community still talk about NCC, but it's really been replaced by the next two terms:  SCWR and CCC.
  • Sleep Capacity Weight Rating (SCWR):  Each RV, even within the same line or model, may have different "official" sleeping capacities.  My RV officially sleeps four people, while someone else who ordered my same model with another couch instead of recliners may sleep six people.  The SCWR is the official number of sleepers times 154 pounds.
  • Cargo Carrying Capacity (CCC).  This is the GVWR minus these things:  UVW, SCWR, full potable water tank (include hot water tanks), and full LP gas tanks.  What's left?  Nothing but your actual cargo:  dishes, clothes, lawn chairs, food, etc.
You'll see and hear all of the above terms often.  However, there was a change in 2007 that required motorhomes to have a "motor home occupant and cargo carrying capacity (OCCC)" label posted in the RV.  Newmar posts this type of label and, I would think, other manufacturers do, too.

The OCCC label says "Motor Home Occupant and Cargo Carrying Capacity", and beneath it shows that "Combined Weight of Occupants and Cargo Should Never Exceed XXXX#".  They also say at the bottom of the sticker that fresh water weight is to be included in the cargo, and you also have to include the tongue weight of anything you haul (like a motorcycle you may put on the back of the rig).

This means that you have to take the number on the sticker (4153# in the photo above) and subtract 1) your full water tank capacity (number of gallons times 8.3), 2) estimated weight of passengers and 3) tongue weight of anything you're hauling.  What's left is how many pounds of actual cargo (dishes, clothes, food, spare oil, and anything in the basement storage) you can carry.

In our case, I'm hearing that similarly configured Dutch Star 4369's have labels that show the OCCC as being in the neighborhood of 3300#.  This doesn't leave me much:

3300# - 1100# (full fresh water) - 800# (4 passengers, conservative) = 1400# of cargo.

This doesn't seem like much for all of our cargo.  However, when you add up most of the things you would take on the road, I can't imagine taking 3/4 of a ton of stuff along.  Plus, we can always (if needed) drive with half a freshwater tank and 2/3 of the fuel tank - saving a whopping 800# !  I should note that other 4369's similarly equipped as ours have had OCCC's of 4100+ pounds.  There's a good chance that mine will be in the neighborhood of 3900#, giving me 600 more pounds than my "worst case".

Other ways to get some more cargo storage would be to take away some of the options.  Heating the floor tiles adds another 225 pounds.  The two slide-out storage trays in the basement total 300 pounds.  Removing these options would give us another 525 pounds of cargo capacity.

After considering everything, we think that we can live with the allowance we'll have.  It's quite possible that our OCCC could come in closer to 4000#, in which case we'd have about 700# that I'm not planning on!  Either way, we think we're good so we are proceeding with the options we wanted.

[See Update on Weights for some updated information on this topic.]

Hope all of this helps those of you who are working your own numbers.


  1. The one thing I would add to your important information is balance of weight on each axle. Most critical in diesel pushers (especially those with tag axles) is front axle loading. It is possible to max out the front axle and not be able to use all of the OCCC. In many/most cases the overloading of the front axle can be avoided by proper weight distribution emphasizing heavy items to the back of the coach and basement. In some cases the weight on an empty coach is proportionally high and it may not be possible to load to the GVWR without overloading the front axle.

    1. While I did mention (near the top) that weight distribution is important and that the weight on each axle should be watched, you're certainly right that there should probably be some emphasis on front axle loading. I'll try to update the post with a few more words about it. Thanks for your comment.