How Legit is FifthWheelSt's Calculator?

[hopeisnotastrat]

i'm looking to purchase a new truck and 5th wheel. The 3 trailers we've narrowed it down to are all very similar in terms of GVWR: roughly 15,500 lbs.

The frustrating thing is that I've entered the specs for 2016 GMC HD 3500, 2016 Ram 3500 HD, and 2016 Ford F-350 into the fifthwheelst calculator and it says that none of them can pull any of these trailers.

How is that possible?

I see 5th wheels all over campgrounds with less truck.

[Coach-man]

OK, given the litigation prone society we live in, if I were to publish a 5th wheel tow calculator I would err on the conservative side of every calculation! The result would be a good estimate of 80% of the people using it, but when you start using it for the upward side, you would not get an accurate result! As shown in the calculations. As far as the axel ratings, I read in another blog site that with the Dodge Asian tranny, a 3:83 is the equivalent of a 4:10 rear end, not sure of that but just what I read. In any event axel ratios should not effect weight carrying capacities of the TV.

[JIMNLIN]

The frustrating thing is that I've entered the specs for 2016 GMC HD 3500, 2016 Ram 3500 HD, and 2016 Ford F-350 into the fifthwheelst calculator and it says that none of them can pull any of these trailers.

How is that possible?

I see 5th wheels all over campgrounds with less truck.

Thats because trucks don't carry weight determined by a GVWR or a GCWR or a payload number on a tire placard and especially a RV website calculator. You can use them if you choose to do so as some RV folks do.

Axle and tire load ratings and in particular the trucks RAWR will carry most if not all of the trailer pin weight. These you do not want to exceed.
I assume your trucks is a 3500 SRW with a 7050 RAWR.
These trucks rear axle can weigh in the 3000 lb range which leaves 4050 lbs for a payload which includes the hitch/trailers hitch weight and other gear. Actual numbers depend on actual scaled separate front and rear axle weights.

[avvidclif1]

BobKrogstie wrote:
Your tow vehicle weight is wrong. Not even a semi tractor weighs 15500.

My old 359 Pete weighed 18k. Not unusual for them to go over 20k, tractor only.

So much for that.

[hopeisnotastrat]

B.O. Plenty wrote:
Gas or diesel? BIG difference in what each will haul..

B.O.

Every truck I'm looking at is diesel.

[NC_Hauler]

B.O. Plenty wrote:
Gas or diesel? BIG difference in what each will haul..

B.O.

.

Agree, and it can mean a big difference in towing specs

[B_O__Plenty]

Gas or diesel? BIG difference in what each will haul..

B.O.

[NC_Hauler]

goducks10 wrote:
The real world is different than those calculator worlds. If I use those RV calcs I can't tow my 5th wheel. But if I do in the real world then I'm fine.
I have a 2500 CTD Ram and my 5er is a short light weight one. But the clincher is the 5er has a really high CCC which puts the GVW too high to use with my truck.
If you aren't loading to the GVW the you need to calc out what your real world weights would be. JMO but I would never want to tow a trailer that's maxed out on it's GVW. I like having a cushion for the truck and trailer.

Agree..

[golf_bears]

hopeisnotastrategy'

OK, your now asking the correct questions.

The tire capacity is molded into the sidewall of the tire. Look at the tire rating on the sidewall of your car.

The axle rating is on the sticker pasted on (usually) the driver's door or door frame of the vehicle. Again, look at the one on your car.

If you go to a dealer and check out their truck inventory, check the ratings of the trucks you may be interested in.

I think someone already pointed out in your thread that you should use the GVWR of the RV your interested in to determine if the truck can handle the load. Also, as pointed out use 25% of the GVWR of the RV to determine the pin weight.

You won't make a mistake doing this.

Again, remember, get more truck than you initially need. I can almost guarantee that "Ma-Ma" will want a larger RV down the road!!!!

[goducks10]

The real world is different than those calculator worlds. If I use those RV calcs I can't tow my 5th wheel. But if I do in the real world then I'm fine.
I have a 2500 CTD Ram and my 5er is a short light weight one. But the clincher is the 5er has a really high CCC which puts the GVW too high to use with my truck.
If you aren't loading to the GVW the you need to calc out what your real world weights would be. JMO but I would never want to tow a trailer that's maxed out on it's GVW. I like having a cushion for the truck and trailer.

[NC_Hauler]

hopeisnotastrategy wrote:

golf_bears wrote:
Any one of those trucks will pull those RVs. That is not the problem. The real issues to be concerned about are:
1--- Will the TV rear axle carry the load? What's the TV rear axle rating.
2--- Will the TV tires carry the load? What are they rated for?
3--- Will the truck stop the load?

As suggested, you can change the gear ratio and/or go to a dually.

Personally, I would get a dually with at least a 4.1 gear ratio.

The FifthWheelSt calculator doesn't account for gear ratio. I was always told it impacted your towing, so I'm not sure how to determine how much more (or less) I tow going from the standard 3.42 gear ratio to the 4.1 gear ratio.

Also, how do you determine if the axle will carry the load and if the tires will carry the load?

Though not many care, but one could use the GCWR ratings that the manufacture assigned to said vehicle...That is what is effected by the gearing.

You weigh the truck at a CAT scale, full of fuel, DEF, people, pets,hitch etc....just like you're going camping...Let's say drive axle weight is 3,000# and RAWR is 7,000#, subtract 3,000# from the 7,000# and you have 4,000# left to put toward pin weight. I don't do it this way, but almost everyone else does, and the Law looks at axle ratings/tire weight ratings

I've never seen, ( in my case) A truck sold at a dealership, that didn't have high enough weight rated tires to cover rear axle weight rating...but guess there could be:h...I never owned one that came with tires that couldn't handle RAWR.

[hopeisnotastrat]

golf_bears wrote:
Any one of those trucks will pull those RVs. That is not the problem. The real issues to be concerned about are:
1--- Will the TV rear axle carry the load? What's the TV rear axle rating.
2--- Will the TV tires carry the load? What are they rated for?
3--- Will the truck stop the load?

As suggested, you can change the gear ratio and/or go to a dually.

Personally, I would get a dually with at least a 4.1 gear ratio.

The FifthWheelSt calculator doesn't account for gear ratio. I was always told it impacted your towing, so I'm not sure how to determine how much more (or less) I tow going from the standard 3.42 gear ratio to the 4.1 gear ratio.

Also, how do you determine if the axle will carry the load and if the tires will carry the load?

[NC_Hauler]

I towed a 5er that was loaded to 16,300# with a pin weight of 3460#..This from CAT scale weights and some simple Arithmetic. (Simple subtraction)

Don't really need any special "fill in the blank" calculator to figure if a truck can tow a certain 5er...Just some common sense in weighing one's truck, ready to "hook up and go, and compare to data plate on drivers door, i.e. GVWR, (most don't use this, but I still do), BUT, look at RAWR and again, just some very simple Math and one ought to be in the ball park to know if a particular truck can tow a particular 5th. wheel. take 22% of hers GVW and ball park pin weight you'll put in the bed of your truck, (on the hitch)..One should be able to figure out if the need a 3500 SRW truck or a Dually.


A 5er with GVW of 16,000# now? Went up 500#..I like the stability the dually offers, but would think OP should be able to tow 5er he spoke of with his 3500 SRW truck..

[Mike_E_]

Hi,

Here's the numbers for my 2014 Ram 3500 SXT swr:

Payload: 4026lbs
GVWR: 11,700
FAWR: 6000lbs
RAWR: 7000lbs
Towing capacity: 17,600

Currently I am without a trailer :(, but with these ratings I am more than comfortable using the truck up to these ratings. This is just ME....notice I said "up to" these ratings. Over? Not on my life.

It's amazing the numbers the newer trucks have. When I started RV'ing back in '08 the above numbers would have been reserved for dually long-boxes. That's why I think it's hard to wrap our minds around the current posted capabilities of newer trucks.

Put a 40 foot fifth wheel with 16K GVWR in a parking lot with a new DWR and SWR next to it and ask most folks which truck could handle it and I bet a majority would only point at the dually, when in fact both 'could' do it. The DWR would have more 'breathing room' numbers wise, but the SWR could be used safely as well.
It does seem "odd" that a short-box SRW truck can tow so much, but who am I to second-guess engineers. 😉

Again, this is MY take, and I would have no problem using my truck as designed.
Must mention that my truck is only slightly above 'bare bones' options-wise, which is why I have the Payload rating I have. Obviously there are SRW trucks that wouldn't work with the above mentioned fiver, but mine certainly would 🙂
Can't wait to get the green light to go shopping 🙂 🙂

Mike

[Old-Biscuit]

15,500# GVWR 5vr....WET Pin Weight roughly 3400# (or higher)

ANY current model DUALLY can handle that pin weight

IF you are looking for a SINGLE rear wheel the available payload, trucks GVWR and the GCVWR will be an issue

[BobKrogstie]

Adjust your pin weight percentage selector to 20% and you should be able to tow 17,618 pounds worth of FW. I used 11,500 GVWR of my 2009 RAM dually in this calculation. See my signature for full truck description.