Tow vehicle math help...

June 2, 2020 8:01 AM

I have a 26' Prowler trailer, weight is 4730, max capacity weight is 6730. I am looking to purchase my neighbor's 1998 Eddie Bauer Ford Expedition, with a rebuilt engine, and a tow package. I am trying to figure out if I have enough information...

From what I can find, I 'think' I can use this as a tow vehicle, but I am still confused.

The hitch says:

max gross trailer weight:
weight distributing 8000lbs
weight carrying 5000lbs

max tongue weight:
weight distributing 800lbs
weight carrying 500lbs

Will this be enough to tow my trailer? What other information do I need to know? Thank you in advance!

posted by MountainDaisy to Travel & Transportation (7 answers total)

The tow capacity of a 1998 Eddie Bauer Ford Expedition appears to be 6100 pounds. I don't have a Ford Expedition - it would be a good idea for you to independently verify that number. The 6100 pound number is with the Ford towing package, not any third party package. You should check that the towing package on the vehicle is from Ford and not, say, U-Haul, since a third party towing package may have significantly different capacities and/or may be installed poorly.

You will need a weight distribution hitch, and I strongly recommend getting one with sway control. Not all weight distribution hitches have sway control, although most do. Your trailer will weigh about the same as your vehicle and is physically larger than your vehicle, so your vehicle dynamics will be driven more by the trailer than your vehicle - all the reason to ensure your trailer stays put while driving.

You will need to apply some common sense to not overload your trailer or unbalance weight on your trailer. You will only be able to load 1370 lbs of cargo in the trailer (6100 lb - 4730 lb) since you will be limited by your Expedition and not the trailer. You'll want that cargo to be roughly balanced around the trailer to ensure even weight distribution and to avoid placing too much weight on the hitch tongue. I wouldn't worry about that though, too much, other than to ensure you don't place all cargo towards the front or back of the trailer.
posted by saeculorum at 8:28 AM on June 2, 2020 [1 favorite]

You will probably run out of tongue weight or payload capacity before you ever get close to the max tow capacity.

Tongue weight on a travel trailer should be 13-15% of total weight of the trailer, so you are looking at a tongue weight of 875 lbs on the low end with a max of 800 on your tow vehicle.

Google says the payload should be around 2,000 lbs, so you might be good with that number. You should always do your towing math using the max trailer capacity. There are other numbers to look at also to make sure you are in the safe zone. I recommend using a towing calculator to see all the numbers.

Here is one towing calculator
posted by Broken Ankle at 8:29 AM on June 2, 2020 [2 favorites]

Response by poster: Thank you. I did put in the info into the towing calculator and received the output below. Does that mean it is ok, because it is 1242 under max? (I apologize for my ignorance, I'm still learning this stuff. I will also be measuring everything and switch out to a sway bar hitch when I can, if it is not a sway bar hitch already.)

Towing Information
Vehicle: ford expedition
Curb Weight: 4808
GCVWR: 13500
Payload rating: 2000
Passengers: 250
Cargo: 500 (I'm guessing here.)
Trailer: 4700
Trailer GVWR: 6750
Hitch Weight: 670 (It told me to take 10% of full trailer weight)
Calculate Clear

ford expedition pulling the 4700:
Under payload (2000) by 580
Acceptable GCVW. Combined weight = 12258. Under GCVWR by 1242
posted by MountainDaisy at 10:12 AM on June 2, 2020

In addition to the checks you are already doing, you will want to get your loaded trailer weighed (usually you can do this for free on commercial scales if you ask nicely; they likely also have a set of scales at your local landfill), because it might weigh more than the factory says it does, and the stuff you put inside may weigh more than you think it does. That way you are confirming that things are within limits in the real world.

Personally I really hate towing near the maximum of what a vehicle is rated for except for short across-town trips. It feels much better to be more in the 1/2 to 2/3 range of the rating in terms of handling and braking.
posted by Dip Flash at 10:49 AM on June 2, 2020 [5 favorites]

Never overestimate the towing capacity of your rig.
These numbers are based on optimal conditions.

Problems that can lead to property damage and injury/death:
You are over-weighted or top-heavy, or weight is badly distributed within the RV. You have trouble with your tow vehicle (engine, transmission, brakes, axles, hitch). You have trouble with your RV (brakes, axles, hitch, frame). You have trouble with any/all of your tires including air pressure and tread.
Many of these mechanical issues can be avoided, but a blowout can happen without warning.

You are driving in bad weather conditions, are on a badly maintained or difficult-to-navigate stretch of road, are driving in heavy traffic with unpredictable actions by other drivers, are driving in the country and encounter an animal in the road or some other unforeseen obstacle. These include issues that are out of your control.
If you cannot stop safely due to a too-heavy rig, you will have few good options.

Robin Barrett at Creativity RV.com has several books and a YouTube series, including information on RV and motorhome insurance worth looking at. She was formerly employed in the insurance industry.

Robin and former van dweller Casey Roman have both switched this winter to fifth wheel and large truck life. Here is Casey's "Bob" tour: towing trucks for big trailers, which includes information from electrician Michael Hamby of Bluewater Marine & RV (at 13:15) who has strong opinions about what tow vehicles should and should not be required to do. Casey is a photojournalist previously working in broadcast news in North Carolina.
posted by TrishaU at 1:44 PM on June 2, 2020

I think your margins are too close, or they would be for me. The thing you have to remember is that the mfrs stated weight of 4730 on the trailer is really almost certainly less than the trailer actually is. They lie. All the time. And, even if they are correct, that’s dry weight so no water in the tanks, which is where your main weight comes from. You will need to have water, if you’re boondocking, and then afterwards your gray/black tanks will be full, not to mention gear and food and etc - the weight adds up really quickly. An Expedition is an SUV not a truck and a 26’ trailer is a big trailer. If you’re just planning short trips, no mountains, not a lot of highway, you’ll probably be fine. But if you want to do anything else? I’d look for a real truck.
posted by mygothlaundry at 4:01 PM on June 2, 2020 [3 favorites]

This is tangential to your question, but aside from the concerns the other posters raised, with a tow vehicle of that age I would take a very careful look at the condition of the metal brake lines (critical if you're in the rust belt) and the condition of the rubber brake hoses which probably should be changed due to age alone.
posted by Larry David Syndrome at 7:26 PM on June 2, 2020 [2 favorites]