Choosing the Right Tow Vehicle

February 15, 2008
Filed under Towing Guide, Towing Tips, Trailer How To

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Ah, decisions, decisions. With so many choices available in tow vehicles, selecting the one
that works best for your application may seem like a monumental task. After all, there are
many variables to consider, including budget, brand and towing capacity, it’s important to
examine them all carefully before making a purchase. Going through the effort to better
understand each variable and to account for all of them up front will lead to a more
pleasant trailering experience later.

Words of Wisdom
The tow-ratings
guide in this section lists the maximum tow ratings for vehicles with specific equipment,
but for many vehicles the maximum tow rating is optimistic. Always check with the
manufacturer before making a purchase. What follows is a layman’s explanation of the terms
you need to know which, when combined with readings from a public scale and your own
calculator, should help you determine the correct tow rating for the tow vehicle you plan
to buy.

Gross Combination Weight Rating (gcwr): The total allowable weight
of the truck, the trailer, the cargo in each, fluids and occupants.

Gross Vehicle
Weight Rating (gvwr):
The total allowable weight for the vehicle, including
fluids, options, occupants, hitch, cargo and trailer hitch weight. The trailer’s gvwr,
sometimes referred to as Gross Trailer Weight Rating, is the total allowable weight of the
trailer, fluids, occupants, options and cargo.

Gross Axle Weight Rating
(gawr):
The total allowable weight on any given individual axle. Note that this
includes the weight of the tires, wheels, brakes and axle itself.

Maximum Tow
Rating:
The manufacturer’s weight limit for towed loads. For conventional
trailers, this normally includes a hitch-weight limit as well; for fifth-wheels, the pin
weight is applied to the truck’s gvwr and its rear-axle gawr. The gvwr and gawr for all
motor vehicles are listed on the data plate, typically affixed to the driver’s door frame,
fuel door, glove box, end of the dashboard or other easy-to-access location. Brochures and
window stickers may be inaccurate. All trailers should have a weight sticker — normally
found in an interior cabinet — that lists the trailer’s

1452097_towing.jpgUnloaded Vehicle Weight (uvw),
gvwr, weight added by freshwater and LP-gas and the resulting payload capability. In many
cases, optional equipment — such as air-conditioning units, generators and the fuel they
run on — sneaks onboard after weighing, and may not be reflected on the sticker. And don’t
forget the fuel-fill tanks that some SURVs offer for campground refueling of motorcycles
and ATVs. The gvwr figures are neither guidelines nor estimates; they are limits, and there
are numerous valid reasons the manufacturer arrived at the figures given. If you think
these figures are “close enough” or have a fudge-factor percentage built in, think again.
Your warranty coverage — and your safety — may be at risk.

There is one sure way to find
out what your trailer weighs, and that is to fill it with everything you normally travel
with, right down to the soap and soda, and weigh it at a public truck scale. Without
forming a long queue, get the hitch weight, axle weight and total weight. Assuming that the
axle weight is below the gawr, the total is below the gvwr and the hitch weight is below
the maximum given for your tow vehicle, you can then move on to tow-vehicle selection.

For
a new trailer, consult the weight sticker on the unit of your choice on a dealer’s lot and
refer to the uvw and Cargo Carrying Capacity (ccc). Estimate how much cargo you will add,
being mindful of the gvwr, and use that number while selecting a tow vehicle. To a lesser
extent, tow-vehicle weight is variable as well. Brochures and tow guides frequently list
how much a truck weighs, but this number generally applies to the most basic model in that
configuration, without any options. In some cases, distinctions are made by engine,
transmission, drive system (2WD or 4WD/AWD) and, in other cases, by cab or bed styles.

If
the dealer does not have a vehicle equipped as you want that is available to weigh, or
cannot provide option weights, you can form rough estimates. Bigger engines add weight,
diesels more so because they come with additional accessories; 700 pounds more than the
standard gas engine is common. Add up to 175 pounds for an optional transmission, about 400
pounds for 4WD and a bit less than 300 pounds for longer beds. Then add other options such
as luxury-trim levels, as all those electric motors add up. The towing package and hitch
could go another 100 pounds, and even larger wheels, two-tone paint and exterior trim can
also have an effect.

The following is how to calculate the realistic towing capacity of the
vehicle that interests you. For example: Consider a fictional one-ton longbed, diesel,
extended cab, 2WD, single-rear-wheel pickup set up for towing. We’ll arbitrarily assign it
a gvwr of 9,900 pounds, a front gawr of 5,000 pounds, a rear gawr of 6,824 pounds, a gcwr
of 23,000 pounds and a quoted maximum tow rating of 17,000 pounds. As is often the case in
single-rear-wheel trucks, the rear axle’s gawr on this truck is derived from each tire’s
maximum load of 3,412 pounds. Pickups such as this normally start at more than 6,000
pounds, and with a diesel, automatic and nice trim, figure that with a full tank of fuel
and hitch, this unit weighs 7,000 pounds. If we add two “standard-size” people (154 pounds
each), a few tools and some cargo, it weighs 7,500 pounds. That is split to 4,000 pounds on
the front axle, and 3,500 pounds on the rear axle.

The first thing you should have noticed
is that the maximum tow rating cannot apply with the truck fully loaded because gcwr
(23,000) minus gvwr (9,900) leaves 13,100 pounds — about two tons less than quoted towing
ability. After adding options and people to the example truck, and subtracting that value
(7,500) from gcwr (23,000), the effective working tow rating of the truck becomes 15,500
pounds, about 1,500 pounds less than the truck’s quoted maximum towing rating.

However, you
have yet to check all the numbers and verify that a 15,500-pound trailer will work. If that
trailer is a fifth-wheel and has 20 percent of its weight on the pin, that adds 3,100
pounds to the back of the truck. This would make the truck overweight — its 7,500-pound
ready-to-roll weight plus the 3,100 pounds on the pin equals 10,600 pounds — 700 pounds
more than the truck’s gvwr, and just 224 pounds shy of the rear-axle limit of 6,824 pounds.
SUVs cannot always escape either. The vehicle’s loaded weight must be subtracted from the
gcwr to determine the realistic tow rating.

Consider This
The tow-ratings
chart lists vehicle-towing maximums segregated by engine, cab style, drive and single- or
dual-rear wheels as appropriate. In general, assume the maximum tow rating always requires
a towing package — special towing equipment (see “Towing-Package Essentials”) — and the
highest numerical axle ratio offered, and as the example shows, maximums can be confusing.
You can do your own estimates by starting with the information given and keeping the
following generalizations in mind.

Transmission: For the majority of
vehicles, automatic transmissions offer the higher tow ratings when they vary by
transmission. On heavy-duty (HD) models, the difference may be 1,000 pounds or less, and on
lighter-duty vehicles, a manual might rate a 2,000-pound lower tow rating. Exceptions
include high-output engines that are available only with manual gearboxes, vehicles where
the manual weighs more than the automatic and transmissions in vehicles designed for high
performance and not towing.

1452097_Fig1.jpgAxle Ratio: Lower gearing (the numerically
higher ratios, e.g. 4.10:1, 4.56:1, as opposed to 3.55:1, 3.73:1), typically produces the
highest tow ratings because of greater torque multiplication. There is wide variance in the
axle ratio’s effect on tow rating, with some diesel-powered rigs varying only a few hundred
pounds. On others, changing from a 3.73:1 to a 4.30:1 sometimes increases the tow rating by
3,500 pounds. In the past, some ratings have increased by a factor greater than three (from
2,000 to 7,100 pounds) simply by using a different axle ratio. Lower gearing will also make
your vehicle accelerate quicker up to 50-55 mph. In general, a one-step drop in axle ratio
(4.10:1 to 3.73:1) on an HD pickup will drop tow rating and gcwr by a ton. Lower gearing
has an adverse effect on fuel economy, but it’s usually not proportional to the gain in
towing ability. Under the best circumstances, the difference between the highest and lowest
gear ratios offered (say, 3.42:1 and 4.10:1) results in a 1.5-mpg decrease in non-towing,
steady state-highway cruising. In most conditions that change is less than 1 mpg, and if
you tow a relatively heavy trailer a lot, there’s no question that the lowest gearing is
best.

Drive System: Vehicles that drive only two wheels, be they front or
rear, generally have higher tow ratings (all other things being equal). Even though modern
4WD and AWD systems are quite efficient, a small amount of parasitic loss uses up energy.
More importantly, 4WD systems add weight — easily up to 400 pounds on some HD pickups –
and that weight frequently comes off the tow rating. Unless the gcwr and gvwr are higher, a
4WD version will probably tow a few hundred pounds less than its 2WD counterpart.

Towing Package: If you can order a towing package, do so. Not only is it
usually required to get the top tow rating, the contents rarely can be duplicated for the
original cost — and it will add to resale value. Frequently you can see the hitch or tow
plug, but there are often changes to the wiring system (including up-rated wire and fuses),
alternator, battery, cooling system, power steering and lubricants.

Bed
Length/Style:
If there’s a difference, a longbed truck may rate slightly lower in
tow capacity — 150-250 pounds — because the longer bed adds weight. On other cases there
is no change because the longer wheelbase is beneficial. Note that the more “styled” beds
marketed under a variety of names typically are heavier than conventional slab-sided beds,
and that cab-and-chassis figures do not reflect any bed unless otherwise noted. A steel bed
for a medium-duty cab-and-chassis could quickly eat up an entire ton of its gcwr.

Single or Dual Rear Wheels: Most people assume that a dually pickup will
have a higher tow rating than a single-rear wheel unit, but this is not correct. In many
cases the gcwr is limited by factors other than the number of rear wheels and does not
change, and in those cases the weight of the wider axle, bigger brakes and two more tires
and wheels is subtracted from the gcwr. The dually no doubt provides a more stable towing
platform for the heavier trailers, although not always with the highest tow rating.

Tires: Wheel sizes continue to grow commensurate with their popularity,
with some tow vehicles offering 20-inch-diameter wheels as factory options. However, using
a larger wheel and lower-profile tire means a smaller air cushion and lower tire sidewall,
to the extent that tow ratings generally drop whenever the wheel size increases. Be sure to
read the fine print on the packaging carefully.

The Hardware Store
Before
purchasing any vehicle for towing, ensure that the equipment required is available for your
vehicle. You may find that the new-kid-on-the-block is a very capable tow vehicle, but no
one makes a fifth-wheel hitch for it. Also beware of hitch-ball and receiver ratings, as
some trucks are rated for heavier loads than any easily found hardware can handle, and
therefore may require special-order parts. Before making a purchase of a new vehicle, we
also suggest that you acquire the manufacturer’s comprehensive towing guide, available
online or at dealerships. Be sure to read the fine print in the guide because in many cases
the maximum rating may apply only to one particular version and be for a fifth-wheel
trailer; many larger pickups may have their actual tow rating limited by the hitch and
hardware. Remember that the powertrains used in some vehicles may not be available in each
of the 50 states or Canada. Also, keep in mind that manufacturers provide tow ratings based
on a fully loaded vehicle, one with two or four passengers or a vehicle with just a driver
on board, and in some cases tow ratings include frontal area of the trailer as a
consideration.

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Comments

2 Responses to “Choosing the Right Tow Vehicle”

  1. Protect Your Automatic Transmission; Do’s and Don’ts - ETE Reman - Protect Your Automatic Transmission on March 5th, 2013 9:27 pm

    [...] Don’t tow over the vehicle’s recommended towing limit or carry payloads over the recommended limit. This puts a lot of stress on the transmission and can [...]

  2. towing / gvrw sticker - Ford Powerstroke Diesel Forum on March 29th, 2013 4:31 am

    [...] you may want to get actual weights from a scale. If you want to get specifics, check these out: Choosing the Right Tow Vehicle RV Camping & RV Lifestyle – Changin' Gears (at the bottom check out Travel Trailer Weight [...]

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