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Author Topic: Doing the math  (Read 4319 times)

Ingreen99

  • Posts: 2
Doing the math
« on: March 27, 2006, 12:54:26 AM »
Hi all, I am new to the trailer towing community and have found the information on this site useful in making my decision on purchasing a pull trailer.  (But)

I would like to show my proposal to all who would be kind enough in helping me on my  choice. Here is what I have.

2004 F150 Crew cab FX4 (18” wheels)
GVWR= 7200
GCWR= 14500
Max tow rating= 8700

What I would like to have
Artic fox 23-5A
Dry lbs= 6620

What I will probably choose based on safety and “satisfaction rating”
Keystone Zeppelin Z241
Dry lbs= 4155

I had my truck weighed at the scales with me, a full tank of gas and my toys I usually have in the truck, example: Cold weather gear, guns, maps and a day pack.
This put me at 6200lbs even,( options on the truck include tube brush guard, tub step rails) that’s leaves me with 1000lbs payload to meet my GVWR
OK. When I calculate my weight numbers I’m adding 15-25% of the gross trailer weight for the “23-5A” and 10-15% for the Z241 to the payload of my truck.

The “23-5A” dry puts me at 88% of my GCWR,  76% of my max tow rating, and my GVWR at 99.9-109%!! Add in extras like friends and family to the truck lets say 500lbs and that puts my numbers at 91% GCWR and 106-116% of the trucks GVWR.  Looks kind of risky doesn’t it.

Now with the Z241, the numbers are a little less stressfull.”Z241” Dry weight of 4155lbs me and my toys, (no friends and family) puts me at 91-94% of the trucks GVWR, 47.76% of the Max tow rating, and 71.41% of the GCWR. Add extras 500lbs for friends and Family and say 376lbs of water and 300 lbs of gear in the trailer (+676lbs) that’s puts my me at 99-103% of my GVWR 55.53% of the Max tow rating, and 79.52% of my GCWR.  These figures do not include a weight distribution kit to spread weight from the truck back to the trailer.

It doesn’t take much thought to decide that the Z241 is the safest of the two trailers. Even if the Z241 was to have its MAX payload on it of 1845lbs and 500 lbs of (friends and Family in the truck) that would still put me at 87.59% of my GCWR 68% of my Tow rating,  but 101-105%!!! of my GVWR.  So with these figures in play, I understand I need to look at all of my “weight” factors GVWR, GCWR, and tow rating. But take the Z241 for example at max possible weight, and 10% tongue weight I/m at 101% of my GVWR but 68% of tow rating and 87% of my GCWR.
1.)   If I can keep my GVW below my GVWR am I “playing safe” with my combined weight at 87% of the GCWR,… Take in mind this is for local short trips.  Long “cross country” trips I would not plan on a water payload.

2.)   Assuming all weight factors are important. Should I try and keep all my weights (GVW, GCW, and tow weight) below 80-90%. I guess what I’m trying to say is “someone stress the importance of GVW”  My current understanding is,  keep it with in the standards, while not overloading the axle,  and as long as my GCW is 80-90% I should be ok, even though I’m operating at high a GVW?

3.)   I have towed the Z241 at the dealership; it was dry with no weight distribution bars added, just me and the Salesman, approx 180 lbs,.. This was just after I had my truck weighed.  The truck pulled very well around the local area, up some decent grades. I would guess 4-5%.  To say I noticed an increase in RPMs would be stretching it, so no noticeable RPM increase.  With these numbers it put me at 97.27% of GVWR 47% tow rating, and 72.66 GCWR.  The truck pulled great! But what kind of risk am I taking with a High GVW and low GCW.

Any input on my two trailer selections would be great and received well!  I already predict the response on the 23-5A,  I can run the numbers in my head all I want, but after writing down the numbers and re-reading them it becomes clear that the 23-5A is stretching if not exceeding the limits of my vehicle. Still any input is well received..  Also looing at the  Z241 given that my numbers are accurate, Does it seem a decent choice?  When loading a truck, natural the lowest numbers I would assume would provide the best answer, but with my GVW tipping at its MAX rating when fully loaded, should I reconsider a “Tow” that would allow lower tongue weight!.

Like I said, suggestions will be gratefully received, and feel free to elaborate.

Ps. Oh yeah give the title of the topic, does my math sound about right =)




Gary RV_Wizard

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Re: Doing the math
« Reply #1 on: March 27, 2006, 09:01:02 AM »
Since you have determined the "real" numbers, you can pretty much ignore the max tow rating, since it is merely an approximation distilled from some marketing assumptions.  Use the actual measured weights, and the trucks GVWR and GCWR. For the Fox fifth wheel, your max towing capacity is the difference between the actual truck GVW (loaded) and the GCWR, or 14,500 - 6200 = 8300 in your case. And since you seem to want to allow an extra 500 lbs load in the truck for the occasional friend and extra gear, reduce that to 7800 lbs.

But if you are getting close to the GCWR or truck GVWR, check that the trailer dry weight is accurate, since they sometimes are low by anywhere from 100-500 lbs. This is especially likely if there are factory installed options and guarunteed if there are dealer-installed options. Ask the dealer if you can take the trailer to a scale, since your numbers are close to the margins (or maybe beyond).

The 1000 lb payload is light for towing a fifth wheel and if you assume another 500 lbs load for friend & gear you are down to 500 lbs. That's simply not enough to carry a fifth wheel's hitch weight. Period.

You also need to be concerned about the truck's Gross Axle Weight Rating (GAWR) on the rear axle. Most of a fifth wheels king pin weight falls direct on the truck's rear axle and can exceed the axle capacity even though the truck as a whole remains under the GVWR. In other words, the rear axle is overloaded while the front axle has plenty of capacity left. You can't transfer weight forward with a fifth wheel hitch like you can with a weight distributing hitch on a travel trailer. I suspect your GAWR is going to be a real limitation on fifth wheel size.

With this truck you can probably tow a larger travel trailer than you can a fifth wheel. A weight distributing hitch will trabsfer some of the load to the front axle and balance your load better.

Personally I like the Arctic Fox & Nash line of trailers and suggest you look at some of their travel trailer models.  See http://www.northwoodmfg.com/2006/index.htm    However, if you have your heart set on a fifth wheel, there are lighter weight fivers than the Fox/Nash brands. Probably not as good quality throughout, but lighter.
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Ingreen99

  • Posts: 2
Re: Doing the math
« Reply #2 on: March 27, 2006, 11:52:02 PM »
Thanks RV Roamer for your input!

 Looking at the Arctic Fox it looks like my biggest down fall is my Trucks Payload.  Like you said 1000lbs is light for towing a fifth wheel. Include the weight of the hitch and tongue and the numbers seem to close for comfort IMO.
When I began to consider my trailer options I said to myself I would not let my "wants" out weight my "need", or safety for that matter. With that being said, my heart isn’t  set on any particular type of trailer, Fifth Wheel or TT.  I am 99% sure that I will go with the Z241, it seems to provide everything we wanted in a trailer, and provides it with-in safe parameters.  I just hope that the quality of A Ultra light trailer isn’t overly compromised for the sake of making it a light trailer. 

Reading the forum I see there are a lot of half/ton owners looking to tow 5th Wheel trailers.  I don’t want to be the one beating a dead horse here, I just wanted to provide the facts of my situation and let other more experienced persons provide some input.  My main goal in my final purchase is going to be.. “What will I be happiest with” and that can only be judged finally by ME.  I’ve looked at the Fox/Nash line of TTs and I too like the quality of the trailers over the other TTs I have looked at.  But IMO I feel the Fox/Nash TTs seemed a little cramped for my taste, considering the AF models I also considered was the 22H, The 22M and 22GQ isn’t available in my area at this time and the dealer stated they don’t carry the 22M because the weight difference vs the 25 models where similar.  :(   Granted I don’t plan on living in the trailer, just using it for weekend outings and the occasional 1-2 week cross country trips.

If anything I hope this post can be used as a reference for other half/ton owners looking to get into the towing scene.  In addition I would like any readers to provide some input with their experience with the Keystone/Zeppelin Travel trailers.  How do they hold up over time,  any bad experience with the quality of the trailer and any good experience they might have had.  I feel the key issue with any product is maintenance.  Preventive maintenance can play wonders on the life cycle of anything someone owns.

Gary RV_Wizard

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Re: Doing the math
« Reply #3 on: March 28, 2006, 08:37:49 AM »
We towed a Wilderness fifth wheel with a 97 Dodge Dakota V8  and were nicely within its capacity. The Dakota is theoretically a smaller truck than an F150 but at the time it had a slightly larger payload, about 1750 lbs with the driver onboard. The truck was 4700 lbs with full fuel, so adding the driver still kept it under 5000.  But the 1988 Wilderness was only about 4400 lbs dry, so more like that Z241 in weight.  Your F150 is very heavy at 6200 lbs with you and gear onboard, and if you add the extra 500 lbs you mentioned it is already pretty much maxed out. Frankly, it's really not enough truck for what you want to carry and tow.

If you want to go with a more robust trailer, consider an F250 in the Single Rear Wheel (SRW) configuration.  The towing capacity jumps immensely and it is a sturdy and capable vehicle compared to the car-like F150. and it's still a nice truck to drive every day.
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL