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Open Roads Forum  >  Travel Trailers  >  General Q&A

 > New Truck - Is My Math Right?

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sliptap

Indiana

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Posted: 03/18/20 06:59am Link  |  Quote  |  Print  |  Notify Moderator

Hi Everyone,

My wife and I recently purchased a truck for towing. I've been running the numbers to see which RV's we could purchase and would appreciate you spot checking my math.

Here are some base specs for my truck:

  • 6600 GVRW
  • 1330 Payload
  • 8000 Towing Capacity
  • GCVWR 13300
  • 5270 Truck Curb Weight


It's a 2018 F150 2.7 Ecoboost. I believe payload is my biggest limiter here.

Let's assume 620 lbs of guests (wife/fake kids/dog) and 125 lbs of additional cargo (WDH and 50 lbs gear).

Where I am stuck is calculating the hitch weight. I've read that I should assume 14% of a trailer's GVWR should align with the hitch weight. So if I assume a 4000lb GVWR trailer, then I would just barely be under my payload limits. That would be 560 lb hitch weight (4000*14%). This would assume I am diligent in what goes in the truck as well as not overloading the payload of the trailer.

The math = 1330 - 620 - 125 - 560 = 25lbs.

Am I correct with the hitch assumption? Am I missing anything else? For reference, we've been looking at Coleman Lantern 17B as a potential trailer and I believe that has roughly 3800 GVWR. I think our saving grace could be filling the truck with water at the camp site.

Thank you for any advice!

* This post was edited 03/18/20 07:22am by sliptap *

JIMNLIN

Oklahoma

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Posted: 03/18/20 07:42am Link  |  Quote  |  Print  |  Notify Moderator

Your question a common one on a rv forum and always gets lots of ideas and opinions.
Looks like your using brochure numbers however the truck GVWR and FAWR/RAWR from the drivers side door post sticker and is all thats needed to figure a safe in the bed payload.

Our pickups carry weight which is limited by the truck FAWR/RAWR and in particular the rear axle as its carrying all of a trailer hitch load plus other gear in the bed.
Load it up with people/gear/WD hitch/etc and drop by a set of scales and weigh the front and rear axles separately. Your trucks rear axle may weigh in the 2100-2200 lb range (estimate).
Next look at the trucks certification placard on the drivers side door post and find its RAWR.
Simply subtract the scaled rear axle number from that RAWR number. Use that as its payload.
Never exceed a RAWR number ie;...tire/rear suspension/rear axle assy/wheel rating.

Scaled axle weight numbers cab be used along with measurement when setting up a WD hitch system.

The reason I'm using the trucks RAWR is in many cases using the mfg GVWR based payload can and have overloaded the trucks RAWR number.

620 lbs of guests?? Usually guest are visiting in the trailer or are they riding in the truck.

Fill the truck with water at the campsite ?? IMO you mean the camper ??


"good judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers

'03 2500 QC Dodge/Cummins HO 3.73 6 speed manual Jacobs Westach
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TomG2

Central Illinois

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Posted: 03/18/20 08:02am Link  |  Quote  |  Print  |  Notify Moderator

"Gross Vehicle Weight" is what Ford says the whole vehicle can be loaded up to. What if the rear axle rating was 20,000 pounds on your F-150? Would that make payload 20,000 pounds? OP: You are on the right track and now need actual scale weights to determine that actual situation.

People always come up with this Rear axle thing and if it was true, Ford would simply have to slip a dually rear axle under a Ranger to make it a towing beast.

Boomerweps

Hills of PA

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Posted: 03/18/20 08:28am Link  |  Quote  |  Print  |  Notify Moderator

Your math is right from the info you have. Actual measured weights are so much better. Use the values from the maker's stickers in driver door frame for max limits.
Loading the truck up as if going camping with people and stuff and getting it CAT (or other) scaled is simplest but you can get the truck weighed empty (if more convenient) and add expected weights from that and be close.
Careful loading and shifting balance in the TT can get your tongue weight where you want it.
I also recommend downloading Ford's Towing Guide for your model year. You can cross reference your truck wheel base, cab type, engine, rear axle ratio, type of factory towing package (if any), and find your factory towing limit.
When I had a lesser tow vehicle, 2008 Ford Explorer V6 with towing package, I cleaned out a lot of excess weight from normally carried stuff from both tow vehicle and trailer to be under my rear gross axle weight rating. Because when CAT Scaled, I was overall within GVWR & GTWR & GCWR, but I was slightly over my TV rear GAWR without the WDH and slightly over my TT GAWR with the WDH!

* This post was edited 03/18/20 08:38am by Boomerweps *


2019 Wolf Pup 16 BHS Limited
2019 F150 SCrew STX SB 5.0 factory tow package

sliptap

Indiana

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Posted: 03/18/20 08:30am Link  |  Quote  |  Print  |  Notify Moderator

Thank you Jim - really appreciate your quick response!

To clarify, my GVWR and Payload values are from the weight sticker inside of the driver door of the truck. To answer your other questions, the sticker states:

  • Payload: 1330 lbs

  • GVWR: 6600 lbs

  • F GAWR: 3450 lbs

  • R GAWR: 3350 lbs



If it helps, I also weighed the truck yesterday at a CAT scale. I filled it full of gas and weighed it with me outside of the truck. Here is the actual truck weight:

  • Steer Axle: 3060 lbs

  • Drive Axle: 2240 lbs

  • Gross: 5300 lbs



So, it looks like my rear axle payload is 3350 - 2240 = 1110 lbs? If my wife and I travel in the front, is most of that weight part of the front axle limit? It's a good thing we aren't chubby because the front axle rating would limit us to roughly 200 lbs each haha.

To answer your last questions, 620 of guests would be me (180 lbs), wife (150 lbs), 2 children at 100 lbs, and a 90 lb dog. Correct on the water - I meant filling the trailer at the camp site, not the truck.

Thanks for walking me through this! I understand that the easiest route is to weight the entire trailer/TV setup. However, I am not sure how to take into account when purchasing a trailer.

Merrykalia

Appalachian (apple at chun) Mtn in the GREAT SW Va

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Posted: 03/18/20 08:53am Link  |  Quote  |  Print  |  Notify Moderator

That is the real problem with half ton pickups from ALL the manufacturers. Unless you special order something, most of the trucks sitting on the lots are VERY limited with payload. They look pretty and all the additional "pretties" also eat up your payload numbers.

I would guess and say that 50% of the people out there that purchase their first truck and camper are over their specs. Maybe not grossly overweight, but......

A little knowledge up-front will make you feel better and will make for a better experience.


2017 Ford F350 Crew Cab 6.7L 4x4 DRW

Boomerweps

Hills of PA

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Posted: 03/18/20 08:56am Link  |  Quote  |  Print  |  Notify Moderator

Wow! That is complete as I've ever seen on prepurchase weight considerations[emoticon] Better than I did.
It appears you verified the factory CC, them 1330, CAT 1300.
I just assume truck cab contents just gets shared front and back. Not like a long airplane, spaceship or submarine where weight location can be extremely critical [emoticon]
Ford has three different "towing packages".
53B just hitch and electrical harness
53A standard Tow Package
53C Max Towing package
Each has different rear axle ratios and I just found out recently, each may have different thickness of metal in the frame.

Boomerweps

Hills of PA

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Posted: 03/18/20 09:07am Link  |  Quote  |  Print  |  Notify Moderator

4WD Super cab or supercrew with a 145" WB with 3.73 axle if the ratings GVWR & GTR are the same between 2018 & 2019, using the 2019 towing guide. Got me curious.

Lwiddis

Kern County, CA

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Posted: 03/18/20 09:19am Link  |  Quote  |  Print  |  Notify Moderator

Sorry. It’s done but you violated the rule...buy or select the TT/5er first, then match a truck to it. My wife’s Equinox has almost as much payload as your truck.


Winnebago 2101DS TT & 2020 Chevy Silverado 1500 LTZ Z71, 300 watts solar-parallel & MPPT, Trojan T-125s. TALL pole for flags. Prefer USFS, COE, BLM, NPS, TVA, USF&WS, state & county camps. Bicyclist! 14 year Army vet - 11B40 then 11A - (MOS 1542 & 1560)


sliptap

Indiana

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Posted: 03/18/20 09:19am Link  |  Quote  |  Print  |  Notify Moderator

Thank you everyone for jumping in with your support and kind words! My biggest concern at this point is "how do I estimate which RVs have a trailer hitch weight I can support?" I know this will be an estimate, but I want to be careful I don't overload my truck from the start. Is 14% of the trailers GVWR a safe assumption for purchasing? Or any other advice to estimate this?

I would use a scale to weigh after purchase, but not sure I have that option when purchasing.

@Boomerweps - you are correct on the values! My truck has the 53A standard tow package. Max Tow Package is only available for 3.5 ecoboost. Thanks again for the previous advice also.

@Merrykalia - agreed. Hind sight is always 20/20. On the flip side, it REALLY is a nice truck haha.

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