How much of a tow weight margin is best?

[V'sGlassSleeper]

Hi All,

We are planning to tow with a v-6 Nissan Frontier 4 x 4. The NISMO package (for off-roading, which is what we would like to get) has a max tow capacity of 6,100 bs., and the 4 x 4 SE version has a tow rating of 6,300 lbs.

Initially, we thought we would want to maintain a 1,500 lb. margin between the tow vehicle's max and GVWR of the trailer-to-be, but after reading a forum on the sleep capacity of the 17.5G and CB Bigfoot trailers, we are looking at other options. The 25B21RB has a dry weight of 3690, but unfortunately a GVWR of 7,500, which is way too heavy for us (darn it, because that or the FB would be our dream TT).

Someone on another thread mentioned towing a Bigfoot fifth wheel with a Tacoma, but I do not see any fifth wheels on the Bigfoot website.

Escape has a fifth wheel that is only 19' long, but weighs in with a GVWR of well under 5,000 lbs.

If we go with the Frontier rated to tow max of 6,100 lbs., would we still be doing okay if we keep the maximum weight of what we are towing to 500 lbs. LESS than the max towing capacity of the tow vehicle, or is that asking for trouble?

Also, does anyone know how much water weighs per gallon? Propane?

Thanks for any input!
Val Zeff

[Vivian]

One rule of thumb is to not exceed 75% of your towing capacity for optimal safety.
This website provides valuable information about weights:
http://www.aonrecreation.com/newsletters/drivesaf?id=25

Vivian

[V'sGlassSleeper]

One rule of thumb is to not exceed 75% of your towing capacity for optimal safety.
This website provides valuable information about weights:
http://www.aonrecreation.com/newsletters/drivesaf?id=25

Vivian

Whoaa! That does mean about 5,000 lbs. GVWR total, period. Thanks Vivian... I will check out that website.

For the record, two Bigfoot dealers have tried to sell me on buying the 21 foot model and when I've asked about the GVWR being 1,500 lbs. OVER my prospective truck's towing capacity, they've told me that the GVWR is overstated and that we could easily tow this model. But my research, the Consumer RV Group data and getting on these forums has convinced me that there must always be a safety margin and never to exceed the tow capacity. I am disappointed that the dealers would suggest otherwise. One even told me that the truck manufacturers understate what their trucks can safely tow--actually, I would tend to think just the opposite.

[Brian B-P]

...The 25B21RB has a dry weight of 3690, but unfortunately a GVWR of 7,500, which is way too heavy for us ...

The GVWR (Gross Vehicle Weight Rating) of a trailer is how much it is allowed to weigh, and you don't need to load it up that much. Physically, the relevant weight is what is will weigh when you have it loaded; legally, you may find some rules related to the trailer rating (GVWR), but I don't know if that's really a concern.

The GVWR of some trailers is not closely related to a realistic towing weight, but has more to do with the capacity of the axles and tires.

Why add planned water and cargo allowances to the dry weight, and plan based on that?

[Brian B-P]

If we go with the Frontier rated to tow max of 6,100 lbs., would we still be doing okay if we keep the maximum weight of what we are towing to 500 lbs. LESS than the max towing capacity of the tow vehicle, or is that asking for trouble?

The truck, driver, passengers, cargo, and loaded trailer must all fit with the Gross Combined Weight Rating (GCWR)... and when you look that up I think you'll find that the Frontier's towing limit is based on the assumption that the truck contains nothing but the driver - no passengers or cargo. The 500 lb allowance would mean that your passenger(s) and your stuff in the truck is assumed to be no more than 500 lb, and if it's the whole 500 you have zero margin left.

Unlike some others, I don't see zero margin as a big problem. The rated limits should be obeyed, but they're not ultimate breaking strength - you're not on the edge of destruction at the limit.

[V'sGlassSleeper]

The GVWR (Gross Vehicle Weight Rating) of a trailer is how much it is allowed to weigh, and you don't need to load it up that much. Physically, the relevant weight is what is will weigh when you have it loaded; legally, you may find some rules related to the trailer rating (GVWR), but I don't know if that's really a concern.

The GVWR of some trailers is not closely related to a realistic towing weight, but has more to do with the capacity of the axles and tires.

Why add planned water and cargo allowances to the dry weight, and plan based on that?

Thanks, Brian, I see what you mean and that sounds reasonable to me...
I was starting to add up the weight of the water, propane, and the two of us, but will need to know the weight of each dealer option that is not included in the unloaded vehicle weight (I wonder if the manufacturer would provide that if I call them or email them? It would be much simpler if they posted that info on their website).

Also, I am not quite sure how to estimate what food, cooking utensils, clothing, toiletries, a small TV-DVD combo, outdoor furniture and a much-desired add-on screen room etc. would come to...I guess I can buy a scale and stand on it with most of these items and see what they weigh--is there an easier way to do it than that since we don't have the truck or trailer yet? Should I maybe go get my little Altima weighed, then load it up with everything that we would take in the trailer and go with my partner to a weighing station and see what it weighs and then subtract the first weight from the second? How does one find a weighing station and would they let me do this?

I am concerned about safety... if the actual dry weight (with all options we want) was around 4000 and we added 1,500-1,800 in cargo weight (that is just a guesstimate, since I haven't added everything up yet), that would put us at 5,500-5,800, which is 90-95% of the maximum tow rating, which seems excessive.

I guess this is why many people opt for larger tow vehicles, but we wanted to stay with a truck that felt more like a car, so we have to be willing to stick with lower tow weights. Sigh.

[Brian B-P]

...I am concerned about safety... if the actual dry weight (with all options we want) was around 4000 and we added 1,500-1,800 in cargo weight (that is just a guesstimate, since I haven't added everything up yet), that would put us at 5,500-5,800, which is 90-95% of the maximum tow rating, which seems excessive.

I agree it's too high... in part because you still need to add in yourself and the cargo in the tow vehicle, but in part because 1,500 lb is a whopping load of cargo for the trailer. We only have about 600 lb of this before we hit our Boler's GVWR, and while we use all of that allowance, it's enough.

What do other 25B17.5 owners find that their fully loaded "going down the road" weight is?

[Brian B-P]

Also, does anyone know how much water weighs per gallon? Propane?

[b]Water is one kilogram per litre, or about 8.35 lb per US gallon, so the 115 L (30 US gal) freshwater tank on a 25B17.5 will carry 115 kg (253 lb) of water.

[b]Propane on trailers is in portable tanks, which are rated by their weight capacity, not volume. Since the empty trailer weight should include empty tanks (since they're a standard feature), just add their capacity (two at 20 lb each for a 25B17.5). If you're starting with a weight with no tanks at all, it is really close to assume the empty tank weighs as much as it carries, so a "20 lb" tank is 20 lb empty, and 40 lb full.

All RVs sold in Canada now have a sticker in them showing the Cargo Carrying Capacity (CCC), calculated as the Gross Vehicle Weight Rating (GVWR), minus Unloaded Vehicle Weight (UVW), minus the water in a full freshwater tank and water heater, minus the full propane load. The sticker shows the calculation in detail, so all the numbers you need are available from Bigfoot or a dealer - or by knowing to look for the sticker - as long as they do the same for the U.S.

[V'sGlassSleeper]

I agree it's too high... in part because you still need to add in yourself and the cargo in the tow vehicle, but in part because 1,500 lb is a whopping load of cargo for the trailer. We only have about 600 lb of this before we hit our Boler's GVWR, and while we use all of that allowance, it's enough.

What do other 25B17.5 owners find that their fully loaded "going down the road" weight is?

Hmmm... 2 of us = 310 lbs. + 600-800 lbs. of cargo = 910 to 1100 lbs. cargo, so I guess I was estimating a little high, but I was trying to consider any options that the dealer installed that were not counted in the dry weight listed.

We are likely to boondock for as much as a couple weeks, but could very easily keep the water weight down by carrying less fresh water on the road and going with the truck to get more as we need it. There are probably some really good ideas on keeping the weight down that we just are not aware of because we are total newbies... all suggestions are much appreciated. Getting quite an education in this process!

[Brian B-P]

Hmmm... 2 of us = 310 lbs. + 600-800 lbs. of cargo = 910 to 1100 lbs. cargo...

Ah, I didn't realize that you were including yourself in the "cargo", Val... it does look like you're on the right track, and if 1,800 lb of payload including you and stuff in the truck results in a fully loaded truck and trailer within the GCWR, then the amount by which that cargo estimate is high is your extra margin.

[V'sGlassSleeper]

Well, although it does seem that we could tow the 21', we double-checked the measurements and it will not fit in our driveway, so we are back to the drawing board!

Unless we could modify the Bigfoot 17CB or FB to have a double bed sized sleeping area (without losing the bathroom), we will have to get an Escape 17' Plan B, an 19' Escape 5.0, or a Casita 16' or 17' Spirit Deluxe.

We'd also consider a Scamp fifth wheel IF the axle and suspension and overall unit would hold up to being taken on washboard, rutted dirt roads (but the RV Consumer group ratings suggest that the Scamp would not hold up well for "rv trekking.")

Those are all well within our size and tow weight limits.

[Roger H]

Val, it's too bad you don't have room for the Bigfoot 21'. I occasionally tow our Bigfoot 25RQ with my Tundra 6cyl extended cab 4WD. It's dry weight as equipped is 5300 lbs. I think the Nissan would do OK with the 21' as it actually has more tow capacity than my Tundra. Regarding the GVWR, my 25' has the same axles as the 21', hence the huge cargo cap. That is significant though, as my Airstream 34' axles were significantly under-rated for the weight of the trailer. The "rated" cargo capacity was almost none. It's better that the axles are heavier than needed. They'll never be overloaded that way.

As far as your cargo... the single heaviest thing you'll carry will be water. If you travel with only a few gallons in the tank, I can't imagine what all else you could carry that could weigh more than about 300lbs INCLUDING food, pots and pans, clothing, and dry goods. 300 lbs is a LOT of "stuff" unless you're a real packrat with what you take.

30 gallons of water at 8 lbs per gallon, though, is 240 lbs!

There are some folks who have shoehorned a 54" wide mattress in the G model 17'.

Roger

[V'sGlassSleeper]

Val, it's too bad you don't have room for the Bigfoot 21'.
There are some folks who have shoehorned a 54" wide mattress in the G model 17'.
Roger

We are going to see if we could shoehorn the G model and still get into the bathroom to pee in the middle of the night (after all, tha huge point of a TT is to not have to use the old aluminum "chamber pot" that we utilize in our tent).

We are SOOO disappointed that the 21' won't fit in our carport! We sure hope that the measurements on the 17' include the tires and axles too, because if there's anything jutting out more than a few inches beyond the 8' exterior width shown in the specs, we won't be able to fit it in our 9.3 foot wide driveway.

Hey... has anyone come out with a really durable, watertight, heavy-duty INFLATABLE travel trailer? Hahaha... (no, we do not want a TrailManor or Hi-Lo...looked at 'em and didn't like 'em...gotta have a hard-sided fiberglass upright...).

[Pete Dumbleton]

Always keep in mind that the RV salesman will tell you the truck you already own can pull it and the truck salesman will tell you the truck can pull the RV you already own. I've had RV salesmen look out the window at my pickup (rated to tow 2,000 lbs) and tell me certainly it could pull the 3,500 lb RV...

One prime reason for the 75% Rule of Thumb is that towing capacity may diminish significantly with altitude. My 98 Ford Ranger's manual states that towing capacity should be reduced by 2% for every 1000' of altitude....

[V'sGlassSleeper]

Always keep in mind that the RV salesman will tell you the truck you already own can pull it and the truck salesman will tell you the truck can pull the RV you already own. I've had RV salesmen look out the window at my pickup (rated to tow 2,000 lbs) and tell me certainly it could pull the 3,500 lb RV...

One prime reason for the 75% Rule of Thumb is that towing capacity may diminish significantly with altitude. My 98 Ford Ranger's manual states that towing capacity should be reduced by 2% for every 1000' of altitude....

Well, that is some consolation for not being able to get the 21' BF trailer into our carport. And I do care that we have an adequate safety margin and enough towing power at higher altitudes, because we will be taking our trailer or fifth everywhere--Flagstaff, White Mountains, Utah, Colorado...whoohooo...now we just need to get the darn thing! And the truck.

[Pete Dumbleton]

One thing that the salesmen may have been alluding to is that some manfs spec the axle (which is generally on what the GVWR is based) with plenty of capacity above the dry weight of the trailer and others spec it to be much closer to the dry weight. This is likely what they were talking about. Without some scale weights of real rigs, it's hard to know what the personal load capacity actually is.

Without getting actual scale weights (hopefully with all travel gear and fluids loaded), the next best conservative estimate is obtained by using the GVWR (the assumption here is that the trailer will never exceed that weight), plus a 15% estimate for the tounge weight (TW is seen as a load on the TV, whereas GVWR is seen as towed weight).