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Author Topic: Towing Analysis Assistance  (Read 433 times)

DaveRB55

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Towing Analysis Assistance
« on: May 19, 2017, 10:14:58 PM »
Hello,

I'm recently retired.  My wife and I have decided to sell out and go RVing full time.  I'm just getting starting to seriously assess a purchase to make this dream a reality.   After much discussion we are leaning toward a fifth wheel.  I first wanted to understand towing capacities to be able to determine what size truck/fifth wheel would be a match as I will have to purchase both.   After several hours of visiting web sites and videos I'm beginning to think I should have gone with a motor home!!!  Every calculation example I've found either uses confusing terminology or asks for data in a manner that I can't find or understand.  I would much rather understand how to solve the problem than fill out an on-lin calculator but either this information is very confusing or I'm getting thick! 

The question is if I buy a certain truck, will I be able to safely pull a particular fifth wheel based on mfg specs.  So,  I'm hoping someone out there more knowledgeable might validate the analysis.    All data is in lbs.  Here is the given information

Tow Vehicle (Chevy 3500 diesel specs)
Curb weight:              7,539      Truck dry vehicle weight - no load, no fuel
Max Payload:       11,420       Believe this is also known as the truck GVWR
Payload:                   4,036       GVWR-Curb weight.  The actual math says the payload should be 3881.  I don't  know why these wouldn't agree but the 4,036 is the MFR data
GCWR               25,300       Max weight rating of trailer,  truck and loadings (people, water, cargo etc)
5th Trailering:             17,200       Max Trailer capacity
 
Fifth Wheel    (from Keystone 35Ft Avalanche data)
Shipping Wt            11,420       Also known as dry weight
Carrying Cap              3,580   
GVWR:                  15,000       Not provided but by definition, it should be the shipping wt + carrying capacity.          From my reading this is also known as the GAWR for the trailer
Hitch Wt                      2,240       Weight of the Pin on the truck.

Given the above information, the question is can the fifth wheel be safely towed.  From my reading there are three concerns:
1.   Is the towing capacity of the truck adequate
2.   The Gross vehicle weight of the truck must not exceed the GVWR of the truck and
3.  The Gross Combined weight of the trailer and truck must not exceed the GCWR of the truck

1.  Towing Capacity.  This was the most straight forward.   Towing capacity of the 3500 Chevy is listed at 17,200 lbs.  The fifth wheel if maxed out with cargo weight is 15,000.   The difference between the tow is 2,200 lbs.  Plenty of margin to tow a heavier fifth wheel in the future.


2.  GVW of the tow vehicle must not exceed its GVWR or max payload.   GVW is the truck curb weight+ people + cargo + fuel (7/bs/gal)+Pin Weight or Hitch weight.  Therefore:
Curb Wt:            7,539
People:           600        (estimating 3 people 200lbs each)
Cargo                 50        (estimate)
Fuel                       252        (36 gal of diesel@ 7lbs/gal)
Pin Wt               2,240
                        _____     
Total            10,681     GVWR is 11420  (11420-10681=739)

It's OK but 739 is only 6% of the rating.  The only way I understand to improve this is to purchase higher rated tires or some other truck modification.   Am I wrong in being concerned that I could be close to exceeding the GVWR.  It seems that if I were to buy a larger RV than the 35 ft example in the future I could be in trouble.  Is the analysis valid? 


3.  Gross Combined Weight of truck and trailer cannot exceed the GCWR of the truck.  Weight of trailer:  This would be the dry weight of the trailer  plus cargo and  water.
 Shipping weight      11,430    Dry Weight
Cargo                      800      Safe estimate of cargo: clothing,equipment,stuff
Water                   1,643    Worst case scenario, all water tanks full (66+49+83=198 gal@ 8.3;bs/gal) 
                         ______
Gross Trailer weight           13,873   


Gross Truck weight            8,441        10,681 from item 1 above less the pin wt (2,240). 
                                     _______
Combined weight          22,314          Truck GCWR = 25,300  (25,300-22314=2,986)

2,986 is plenty of margin


What I would welcome would be some comments on whether I've analyzed this correctly and what flaws in the methodology exist,  if any.  Should I be concerned with Item 2.  It would seem a larger 5th with heavier tongue weight would put me over the edge.

Thanks and look forward to any comments.

Sorry about the format.  When copied over from word it was a mess and inadvertently submitted.  Tried to clean up as much as I could
« Last Edit: May 19, 2017, 10:51:31 PM by DaveRB55 »

Hammster

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Re: Towing Analysis Assistance
« Reply #1 on: May 19, 2017, 10:38:05 PM »
Hello.
2016 GMC Sierra 2500HD Denali. 6.6L Diesel. 4x4
Arctic Fox 22G.

Oldgator73

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Re: Towing Analysis Assistance
« Reply #2 on: May 19, 2017, 10:46:17 PM »
Hello. Seems to be an echo here.
2016 Winnebago Winnie Drop
2016 Nissan Frontier 4x4 Crew Cab
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It's not the weight of the load, it's how you carry it.

Ernie n Tara

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Re: Towing Analysis Assistance
« Reply #3 on: May 20, 2017, 07:37:04 AM »
Critical number is likely Payload. The reason for the difference is that the manufacturer stated number is for the  basic truck while the real  number reflects any additional equipment (king cab, option packages, etc). Use the 38.. number. Overall, looks like it will work. ;D

Ernie
Ernie 'n Tara

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Gary RV_Wizard

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Re: Towing Analysis Assistance
« Reply #4 on: May 20, 2017, 08:05:59 AM »
Please look up terms like GAWR and GVWR in the RVForum Glossary - you have some of them way wrong.  GAWR, for example, is Gross Axle Weight Rating - what any single axle can carry.

The specs you read in a sales brochure or website are for a some configuration of the truck, often the minimal one that yields the largest numbers for capacity. They seldom match any specific truck, which typically has some options installed, but should be fairly close (a few hundred lbs in most cases). Newer trucks have a placard on the door post stating that specific truck's payload, GVWR, and axle GAWRs.

I think you are seriously underestimating the weight of gear you will carry in the trailer.  The only realistic plan is to assume the trailer will weigh its max, i.e. the trailer GVWR (some day, if not on Day One). The truck needs to be capable of that. Use the 15,000 lb GVWR value for that Avalanche. That means the trailer pin weight will be at least 3000 lbs (5W pin weight is a minimum of 20% of loaded weight). The truck has to carry that weight in addition to passengers and gear in the truck. Use the specific truck's payload (CCC) rating on its own placard for that.
Gary
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Summers: Black Mountain, NC
Home: Ocala National Forest, FL

DaveRB55

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Re: Towing Analysis Assistance
« Reply #5 on: May 20, 2017, 11:05:53 AM »
Gary,

Thanks for responding...
Looked up definitions as suggested:

GVWR - Gross Vehicle Weight Rating - the most the vehicle can weigh loaded with passengers & cargo (including the hitch itself and the tongue weight of the trailer).
GAWR - Gross Axle Weight Rating (front and rear) - the most weight that can be placed on either axle. A nose-heavy trailer, while within the towing specs, can sometimes overload the rear axle.

In my example I would say I had the GVWR (15,000) right but the GAWR would be the 3,589 lbs load that could be placed in the trailer correct?

Also If I use the 15,000 GVWR and accompanying tongue weight of 20% (3,000), the calculation increases the tow vehicle GVW to 11,441 just over the 11,420 vehicle rating for a 3500 model.  I'm kind of baffled with this.  During my recent RV trip I saw most 5th wheels being pulled by single axle 2500/3500 diesels.  Many of the 5th wheels were in the 40 ft range.  I'm analyzing a smaller unit and its telling me I need to beef the truck to the next level (dually or something else).  In particular, there was a 40 ft Redwood being pulled by a 2500 single axle with air bags in the springs!   Am I missing something?  I'd like to stay away from a dually as I just don't want to drive that big a vehicle all the time.

grashley

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Re: Towing Analysis Assistance
« Reply #6 on: May 20, 2017, 07:20:42 PM »
Welcome to the Forum!  Thanks for researching before purchase!

many comments!

NEVER believe any spec in published materials!  It uses a base model with very few options and Max tow package.  Every pound of options and accessories must be deducted from these weights.

I have the same question about published payloads that are greater than GVWR - base wt.  Are they that bad at math???????

Payload for any specific truck is, as you said, GVWR - actual truck wt, including a full tank of fuel, NO passengers or cargo.  That number should be on the yellow label on the driver door B pillar.

For any TT or FW, the GVWR usually exceeds the sum of GAWR because part of the load is carried by the tongue or pin.

In my example I would say I had the GVWR (15,000) right but the GAWR would be the 3,589 lbs load that could be placed in the trailer correct?

NO!  GVWR = 15,000# is correct.  The PIN WEIGHT will be 3,000# or more, and this load is directly in the bed of the truck.  These have nothing to do with any trailer load numbers.
The truck rear axle GAWR should exceed  curb or base rear GAWR + pin wt + hitch wt.

My F350 SRW with my wife and I runs into weight issues at about 15,000# FW  GVWR.  It has a GVWR of 11,500#.

Yes, there are many folks towing campers with too small of a truck.  You are not missing something.  Those drivers are missing something.

Based on your numbers, you will be carrying 600# people + 50# cargo + 200# FW hitch + 3000# pin wt = 3850#.  Fuel is already included in Payload.  This fits in your 3881 Payload number, but that number is likely high due to options.

Bottom line is your math appears generally correct.  Some incorrect assumptions come from believing advertising numbers.  The 3500 SRW you are considering is fully capable of pulling a nice FW, just not a really big, nice FW.

Thanks for doing your homework!  Please keep asking questions!
Preacher Gordon
09 Grand Junction 35 TMS - not yet received
2013 F350 Lariat LB SRW Supercab diesel 4X4
Nimrod Series 70 popup (sold)
It's not a dumb question if you do not know the answer.

RVRAC

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Re: Towing Analysis Assistance
« Reply #7 on: May 20, 2017, 10:28:05 PM »
First, welcome to this forum.

Second, you stated: Am I wrong in being concerned that I could be close to exceeding the GVWR.  It seems that if I were to buy a larger RV than the 35 ft example in the future I could be in trouble.  Is the analysis valid? 


Yes, to your concerns.  I think you are close or over your GVWR.  Estimating 50 on cargo, and your pin estimate are unreal in my opinion.
2017 Leprechaun 311 FS
Toad: 2016 Jeep Patriot
American Dolly
Home: WI
Snowbird 6 months/yr.

Gary RV_Wizard

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Re: Towing Analysis Assistance
« Reply #8 on: May 21, 2017, 08:01:41 AM »
Quote
...but the GAWR would be the 3,589 lbs load that could be placed in the trailer correct?

No. GAWR is a capacity rating assigned to an axle by the axle manufacturer. You don't calculate it yourself. Your truck will have GAWRs for the front and rear axles (each unique), and the trailer axle(s) will also have their own GAWR. It's not something you generally have to worry much about because the vehicle manufacturer already used the GAWRs as part of the calculation of GVWR and Payload or CCC.  It is possible to exceed one or more GAWRs while still within the GVWR and Payload ratings, but not very likely unless very close to those limits.
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

DaveRB55

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Re: Towing Analysis Assistance
« Reply #9 on: May 21, 2017, 01:26:02 PM »
Thanks all for the help.   Feel much more confident in being able to identify what will work and how to verify capacities.   Felt a 1 ton single axle will be adequate  for the FW size we are interested in and went today to look at the big 3 truck models with my wife.   Man, those are some large vehicles!  The trucks didn't look so big in front of a fifth wheel but they sure were large standing next to one.
We were both taken aback at just how big they were!    BTW we are both small car owners so picturing ourselves having this truck as our run around car has us second guessing whether we should be thinking MH vs FW.   I guess that's another post topic.   Going to look at MH/FW this week.  Thanks again for lending your experience.

Dave

Arch Hoagland

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Re: Towing Analysis Assistance
« Reply #10 on: May 21, 2017, 05:08:15 PM »
Have you ever owned an RV or used one? 

If not I'd suggest renting a class C for a week or two.

 
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grashley

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Re: Towing Analysis Assistance
« Reply #11 on: May 21, 2017, 09:43:33 PM »
I do not know your situation, but if either "small" car is paid for, keep it for a daily driver AND ADD the truck to the corral for towing duties.  Other advantages include if a car does not start or is in the shop, you can relax. you have options.  We have a '09 Civic, my wife's daily driver, my '01 Miata and the '13 F350 SRW.   Talk about a size difference!  The truck has sufficient Payload to carry the Miata in the bed!  The fuel consumption difference may be sufficient to pay the registration and insurance on the third vehicle.
Preacher Gordon
09 Grand Junction 35 TMS - not yet received
2013 F350 Lariat LB SRW Supercab diesel 4X4
Nimrod Series 70 popup (sold)
It's not a dumb question if you do not know the answer.

DaveRB55

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Re: Towing Analysis Assistance
« Reply #12 on: May 21, 2017, 11:06:27 PM »
For those of you who might be interested:

I've never owned an RV.  My wife and I are interested in going full time.  The first thing we did was rent one and try it for a couple of weeks.  We went on a tour from Dallas thru the Hill country to Corpus and then back up through the Piney woods, staying for the most part in Tx State parks.  We both loved the simplicity and the freedom of it.   We knew renting a small C (25 ft) would get cramped and sure enough it did, however everything we had a concern about could be addressed with more space (and some decent internet).  We're not approaching this lightly...it's been on the discussion table for a couple of years.  We planned this trip not to test a particular RV but to see if we found the lifestyle appealing imagining we would not have a home to come back too.  No worries there.  The only other issue we had on the trip was not having a vehicle to run around in. 

We thought a FW, with its spacious layouts (35 Ft in mind) would be a good option and use the tow to run around in as we saw many folks doing that which led me to the problem that started this thread.  Got that down with the forum assistance and determined a 1 ton would be the right size but after looking at them today, their size seemed rather cumbersome to use when not pulling the trailer.  Frankly running around in a 1 ton once we park it for 5-7 days just doesn't appeal to me or the wife.    We do have a 2012 Civic that we would keep as a toad but keeping this car with a fifth wheel doesn't work for a full time plan.  So now we are back looking at MH's.   I'm learning a lot about all the models and reading other topics from folks before plunking down my money on anything.  This is going to take some time but we are on the path.

Thanks,
Dave

Gary RV_Wizard

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Re: Towing Analysis Assistance
« Reply #13 on: May 22, 2017, 06:49:28 AM »
Take your time - you are doing all the right things.  There are numerous tradeoffs in size, towable vs motorized, advantages while traveling vs parked, etc. The right answer for one of us may not be at all right for you.
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

grashley

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Re: Towing Analysis Assistance
« Reply #14 on: May 22, 2017, 06:18:04 PM »
Take your time - you are doing all the right things.  There are numerous tradeoffs in size, towable vs motorized, advantages while traveling vs parked, etc. The right answer for one of us may not be at all right for you.

EXACTLY!

You are doing the right thing with your research prior to purchase.  As you know, there are many options.  Take your time deciding which one is right for you.  Full time is a BIG step, but it sounds like BOTH of you are on board with this.  Write down your options, and all the advantages and disadvantages of each.  Take your time.

I suspect your best options are  a BIG truck with a roomy FW or a moderate size class A and a toad.  Class A are more convenient while on the road - access to fridge, "facilities".  FW are more roomy while parked.  I believe the Civic must be towed on a dolly. (nice car, too!)

Good luck with your search.  Ask lots of questions.  It is a pleasure to respond to folks doing research ahead of purchase!
Preacher Gordon
09 Grand Junction 35 TMS - not yet received
2013 F350 Lariat LB SRW Supercab diesel 4X4
Nimrod Series 70 popup (sold)
It's not a dumb question if you do not know the answer.

Derby6

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Re: Towing Analysis Assistance
« Reply #15 on: May 22, 2017, 06:44:47 PM »
Why not just tow the fiver with the 2012 civic....Ha Ha Ha.... ;) :D ;D 8)
Agree with all above...your changing direction is not all bad.  So many options and preferences.
2015 Ford Explorer (Wifes Ride)
2011 Ford F350 4x4 Lariat Crew Cab/Long Bed/SRW
2011 Honda Civic-- (Beater with a heater)
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