Reversing wheelbase towing rule of thumb?

[Cory Lewis]

There is a towing wheel base rule thumb that a 110" wheelbase can tow a 20' trailer and then you can add 1' of trailer for each additional 4" of wheelbase.

I have a 4,000 lb biggar trailer that is 16'6" from bumper to tongue hitch. Is it safe to reverse the rule of thumb and conclude that:

20' - 3' = 17'

So 110" wheelbase - (3' x 4") = 98" wheelbase would suffice.

Which means I could tow my trailer safely with a vehicle with a 104" wheelbase.

Does this seem safe?

Assuming I have antisway and weight distribution towing equipment.

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[Robin G]

Cory, All the things you mentioned play into towing. But first and formost having a tow vehicle that has a tow capacity to pull your Biggar would be the smartest thing. Wheel base, sway bar, weight distrubution are all part of the puzzle.

[Cory Lewis]

What I have in mind is an older 1970's blazer. Simple to change parts on and most that have survived to today have many non-original parts. So my guess is it could have whatever suspension, springs, and axels necessary. I was just wondering whether there was a wheelbase below which one shouldn't tow and whether 104" is below the threshold for a trailer the size and weight of the bigger.

Right now I tow with an 85 gmc crew cab long box with a turbocharged diesel engine and a 166" wheelbase. Great for cruising while towing but difficult to park downtown when not used tow.

Am thinking of getting a tow vehicle a little easier to park, plus the blazer could be a convertible in the summer.

[floyd]

Interesting....Where did you get that Rule of thumb? At first blush it seems WAY too simplistic to be usefull.
If you are going to measure trailer length, shouldn't ball to axle(and number of axles) be as much a factor as overall length?
Think about the variation in trailers of the same length between RVs... let alone Boat, utility, car and cargo trailers and how they are loaded.
Think about variation in tow vehicles of similar wheel base....
Of course there does seem to be an insatiable appetite for "rules of thumb"...(saves a lot on homework)

I like towing my Scamp 13 with my Ranger [shortbox, regular cab 114" WB] and it works great for my open car trailer as well.Both are within the "rule of thumb", but...without suggesting limits on others here, I think trailers above 20 feet are generally starting to cross class lines.

Example...Properly equipped, many small crossovers perform very well towing a 16ft fiberglass trailer like a Scamp. Most vary from +-101" to 109"WB.

[BCDave]

The only (overly simplistic) rule of thumb I ever encountered spoke to the relationship between the tug's wheelbase vs the distance from the hitch ball to the trailer's axle (or axles).

However, there are many factors to consider - weight of the tug, tires (esp rear tires) on the tug, weight of the trailer, tongue weight of the trailer, etc. There are many factors at play - the tug has to not only PULL it, but CONTROL it in every situation - uphill, downhill, starting, stopping, around corners, in cross winds, slippery roads etc, etc. Wheelbase is a major factor, but so are many others.

[Robin G]

Originally Posted by Cory Lewis

Right now I tow with an 85 gmc crew cab long box with a turbocharged diesel engine and a 166" wheelbase. Great for cruising while towing but difficult to park downtown when not used tow.

I bet! My Dh towed a backhoe with something simular and it was a beast.

From what I have read I think your calculations are correct. But due take into consideration that with a late 70's Blazer, your talking a short wheel base with a high center point. As far as I can tell, depending on the model year your tow cap is anywhere between 4500 and 5500. So your close some model years, but ok if you watch how much gear you take.

[floyd]

Originally Posted by BCDave

The only (overly simplistic) rule of thumb I ever encountered spoke to the relationship between the tug's wheelbase vs the distance from the hitch ball to the trailer's axle (or axles)..

Never heard that one either, where did you hear it and what were the details?

[Cory Lewis]

Don't recall what I typed in to find that rule of thumb, but when I type "wheelbase towing rule of thumb" into google it is on several of the top listed sites. Could be someone with little knowledge made it up, posted it once, and it got copied to multiple sites, like this one, I don't know the origin.

[Robin G]

Same here, LOL but I googled/bing, Tow capacity versus Wheel base and read from there.


My Dh had a simular chart he used years ago with work trucks towing, loads, etc. So it made sense to me when I read it. Actually read it a couple different places with different posters. So, ?

[Mike Magee]

Seems like I saw that on rv.net forum some time back. Where they got it, I dunno.

[BCDave]

Originally Posted by floyd

Never heard that one either, where did you hear it and what were the details?

Awww gee - now I gotta look it up again - and I had it a couple of days (daze?) ago, too!

I know the wheelbase had to exceed the distance from hitchball to axle(s) but I cannot remember by how much - something like 1.25 times or something like that

[Robin G]

Here's one place I read it. Davidsrvtips.blogspot


But here is some of what Cory and I are talking about and what Dave was saying. You can read more on this guys blogspot.



You'll need 2 measurements, the wheelbase of your tow vehicle, and the total length of the trailer you are pulling (or intend to pull). That length is from the coupler to the back bumper.


The First Guideline
(This guideline was first used by the RV Consumers Group rv.org)

For the first 110" of wheelbase, this allows you 20' of trailer.

For each additional 4" of wheelbase, this gets you 1' more of trailer.

Wheelbase / Trailer length
110" = 20'
114" = 21'
118" = 22'
and so on


The Second Guideline
The distance from the coupler to the rear trailer axle should be no more than twice the wheelbase of the tow vehicle.

Why this second guideline? I think this second guideline applies more to non-RV trailers, like boat or flatbed trailers with short (less height) loads on them. Those types of trailers usually do not have the large vertical surfaces (exterior walls) that would be susceptible to wind. You've probably seen a small SUV or pickup pulling a very large boat, right?



If you look at some of the physics and geometry inherent to travel trailers, you might see why length is an important factor to consider. Ever try to carry a full sheet of plywood (or something similar in size) by yourself, on a windy day? It can be pretty difficult to maintain control. But how about carrying a couple of 2 by 4's on that same windy day? Not so hard, is it? That's because the 2 by 4's do not have the same surface area to catch the wind as the sheet of plywood does. So, in a way, that travel trailer is just like a sheet of plywood for catching the wind.

The next thing to look at is how far the coupler is from the trailer tires? The greater the distance, the lesser the impact it will have on the tow vehicle and the less sway it could create. You will see travel trailers of the same overall length with the axles in different locations. This is probably due to the floor plan or layout of the trailer in order to balance the overall trailer, as well as to provide enough, but not too much, tongue weight.

Finally, the ball, or hitch location. How far is it from the tow vehicle's rear axle? The farther away it is (known as rear overhang), the more leverage the trailer can apply to the tow vehicle and create the possibility for more sway. A Jeep or a Hummer would make great tow vehicles because they have very little rear overhang compared to most pickup trucks and SUV's. Another example of this would be in comparing a 2003 Chevy Tahoe to a 2003 Chevy Suburban. The wheelbase of the two are different, but their wheelbase to rear overhang ratios are almost identical. Therefore, both vehicles should be able to handle the same trailer with similar results as far as length is concerned.

[Orcus79]

The Blazer would be fine, I towed with one and dad has towed with his 75 AWD one just fine, the track width and heft helps keep things on the straight and narrow. As long as there are no lifts added to the suspension.

I have seen a mid 80s fullsize blazer go off the road with a 22ft sticky, everything stayed upright and straight.

[MC1]

Great off road vehicles but the old Blazers were never know for their towing prowess. Do you have an alternative?
A buddy had a trailer like yours (3,500 lbs) and towed it with a Blazer. When the Blazer was sold he thought he would try his Mini Van. To his amazement the Mini Van felt a lot more stable towing the trailer than the Blazer.

[Cory Lewis]

Regarding my alternatives: We had a fully computerized bells and whistles minivan and towed it thrice to the dealership for not starting. The third time they started it easily and declared it healthy I declared that henceforth we would have computer free vehicles. So, desirous of doing my part to preserve some of our Canadian automotive history, i bought a 1960 Frontenac with its nine maple leafs which I figured we'd drive year round. The car enthusiasts around here questioned my plan's wisdom so now it is only a summer driver. It wont pull so, reading on this site that the longer the wheelbase the safer the towing, we got Old Smokey, the aforesaid 20 some foot long truck. My wife exercised her veto and now enjoys a nice Toyota sienna. Unfortunately it won't tow. Also unfortunately she likes driving the Frontenac and thinks my sons will too in a few years. So now I have got myself into the predicament of owning: a 1978 17 foot long fiberglass trailer; a 1960 summer only non-towing Frontenac that my wife has declared hers and my sons'; a non-towing Toyota sienna that my wife likes and drives in winters and when the boys' and their friends' hockey gear won't fit in the Frontenac; and Old Smokey which I can't take downtown and park during the winter. So, I figure the Blazer, being a convertible, might be sellable to the powers that be with the benefits of: convertible so fun in the sun, old so computer free and simple and inexpensive to maintain, short enough for me to park downtown in the winter, long enough to tow the Biggar, if four wheel drive less likely to get stuck in the winter and more likely to get my son who fishes to some nice quiet holes. And, most importantly, rather than ending up owning three vehicles, four if I have to buy another one to be able to park downtown during the winter, I could own only the Toyota and the blazer and have all our goals met (assuming I can get them to view a nice blazer as warmly as the Frontenac. As a final bargaining chip if i have to face an argument questioning my patriotism for selling the Frontenac, i'm willing to go so far as to paint the blazer red and white with a maple leaf on the hood.

Now if anyone can direct me to a non-computer vehicle that is longer than the blazer and shorter than a modern suburban (I guess the old suburbans were about 110 wheelbase) and has some feature, such as convertibility, that I might be able to have the powers that be accept in lieu of the Frontenac's maple leafs, I'd be much obliged.

[DonFromTexas]

In another life, I pulled house trailers around the country. That rule must have not yet been passed, since 80 ft trailers pulled by a 15ft truck was the norm.

[MC1]

Originally Posted by Cory Lewis

a non-towing Toyota sienna that my wife likes.

I have never heard of a "non towing" Sienna. They seem to be so popular for towing, even some TT's. Is yours one of those old ones with the mid engine in the floor???

[Cory Lewis]

It is a 2001. Engine is in front of the windshield and under the hood if that is what you mean. I didn't think any minivan could tow anything larger than one of the shorter fiberglass trailers.

Edit. Just checked Wikipedia and it looks like the mid engine was earlier than ours.

[MC1]

Originally Posted by Cory Lewis

It is a 2001. Engine is in front of the windshield and under the hood if that is what you mean. I didn't think any minivan could tow anything larger than one of the shorter fiberglass trailers.

I hear you Cory. I think that is one of the biggest myths going.

Many of our local RV dealers use Mini Vans as test combo's. They set them up as demo's to show how well they work. Near us in Burlington Ruston RV had a 22' Trailite TT set up with a Ford Freestar. We test drove it and it was great. Another dealer not far from us reported setting up over 500 Mini Vans for towing. Most were TT's. They work great when set up appropriately. This was on the cover of RV Lifestyle magazine a few years ago. Of course the latest crop of mini vans are bigger, heavier, and have more HP and better tranny's.

[Cory Lewis]

Hmmmm. The Toyota pulling the Biggar without damaging the toyota would change the situation.