This article was published in the April 2016 edition of NTEA
News
Question: As a truck
equipment upfitter, we are often asked to add trailer hitches and other trailer
towing devices to the trucks we build for customers. How can we determine proper
trailer hitch rating based on the need?
Answer: Many companies
experience this dilemma when balancing customers’ trailer towing wants with the
performance capability of the selected truck chassis. GCWR (see definition at
end of article) is a key factor in determining trailer towing ability and,
subsequently, correct chassis hitch rating. OEMs decide GCWR based on a variety
of factors, including specific drivetrain components, engine, transmission,
number of drive axles, axle ratios and braking ability. Additionally, they test
chassis towing and stopping performance before determining vehicle GCWR
capabilities.
Most chassis
manufacturers provide trailer towing guides to help determine maximum GCWR based
on vehicle configuration. These publications may have maximum trailer towing
ratings based on conventional or fifth wheel towing. (Login to the
Chassis Manufacturer
Directory
to learn more.) Alternatively, the truck dealer can help determine proper
trailer tow rating using OEM order guide information or their application
engineering department.
The C in GCWR signifies that the combination of
towing vehicle weight and towed vehicle (trailer) weight is included in the
rating. Essentially, trailer towing capacity is equal to GCWR less the total
weight of the towing vehicle, including payload (trailer tow rating = GCWR –
weight of towing vehicle, including payload). When calculating towing vehicle
weight, be sure to include the weight of the chassis, truck body, equipment,
passengers, fuel and payload.
Helpful examples
To assist customers in selecting the
appropriate capacity hitch, conduct a towing vehicle payload analysis, including
all permanent equipment to be installed. This will aid in determining the towing
vehicle’s fully equipped weight. Next, figure out normal payload for daily
vehicle operation.
For
example, a truck has a 13,500-pound gross vehicle weight rating (GVWR),
25,500-pound GCWR, total weight for the towing vehicle with chassis of 6,100
pounds (including fuel), 2,800-pound body weight, 1,750-pound equipment weight
(crane, welder, PTO, air compressor), 450-pound passenger weight (three seats at
150 pounds per seat) and 1,400-pound payload. This vehicle would have a maximum
trailer capability of 13,000 pounds (25,500 pounds – 6,100 pounds –
2,800 pounds – 1,750 pounds – 450 pounds – 1,400 pounds = 13,000 pounds). If the
payload were greater, the trailer towing capacity would be lower. Likewise, with
decreased payload, there would be increased trailer towing
capacity.
A helpful
method for determining maximum trailer towing capacity for a given vehicle,
based on rated GCWR, is to calculate the base weight of the towing vehicle,
including chassis weight, all body and equipment mounted on the chassis, and
driver/passenger load. Using the previous example, maximum trailer tow rating
would be the 25,500-pound GCWR, less the 6,100-pound chassis weight, less the
3,650-pound body and equipment weight, less the 150-pound driver weight —
totaling 15,600 pounds.
However,
there may be other factors to consider when determining actual maximum towing
capacity. It could be limited if the OEM specifies a maximum capacity based on
type of towing (fifth wheel/gooseneck or conventional). Alternatively, if the
chassis has a factory-installed conventional hitch rated for a maximum weight of
9,000 pounds — even though the truck has a higher towing capacity based on GCWR
less the weight of the towing vehicle — maximum trailer towing capacity is
limited by the 9,000-pound rated hitch.
Using the
previous example, a truck with a 25,500-pound GCWR, total weight of 9,900 pounds
and maximum trailer tow capacity of 15,600 pounds, will require a hitch capable
of towing at least 15,600 pounds if the customer wants to maximize vehicle
towing capacity.
If you
have any questions, call NTEA’s Technical Services Department at 800-441-6832
from 8 a.m.–5 p.m. EST, Monday–Friday.
GCWR definition
As defined in
NTEA’s Truck Equipment Handbook: GCWR Abbreviation for Gross
Combination Weight Rating — Represents the entire weight of a vehicle at the
ground with a trailer or trailers, including vehicle, equipment, driver, fuel
and payload (everything that moves with the vehicle). The chassis drivetrain
components, engine, transmission, axle and axle ratio are primary components in
determining a vehicle’s GCWR, provided the proper towing devices are
installed.