17NA087

Service Bulletin
Bulletin No.:
17-NA-087
Date:
May, 2021
INFORMATION
Subject:
Brand:
Cadillac
Characteristics of Wide Low Aspect Ratio Tires, Vehicle Pulls Left or Right, Wanders,
Follows Depressions in Road Surface, Tramlining
Model:
ATS
2013
CTS
2009
CT4
CT5
Chevrolet
Model Year:
from
2020
VIN:
to
from
to
—
—
Engine:
Transmission:
All
All
2019
2021
Camaro
2010
2021
Corvette
2005
2021
SS
2014
2017
Involved Region or Country
North America, Europe, Russia, Middle East, Israel, Argentina, Brazil, Bolivia, Chile,
Colombia, Ecuador, Paraguay, Peru, Uruguay, Japan, GM Korea Company, Cadillac
Korea (South Korea), China, Taiwan, Philippines
Condition
Some customers may comment about their vehicle having a tendency to pull left or right
depending on road conditions. Typical descriptions may refer to the vehicle not tracking
properly or that the car wanders. Additional comments may include that the car follows
grooves or inconsistencies in the road to the extent that the vehicle must be steered or
directed with additional force to overcome these roadway characteristics.
What is Tramlining?
"Tramlining" is an industry term used to describe a
vehicle's tendency to follow the longitudinal ruts and/or
grooves present in the road. (Also called “trough
wander”). The name comes from the feeling on a tram
or trolley as the vehicle follows along the tracks. Any
vehicle can exhibit tramlining due to uneven pavement
or severe rutting in the roads surface. All vehicles
tramline to some degree, however vehicles equipped
with low aspect ratio, wide tires tend to be more
sensitive to this condition.
Turning the steering wheel left or right slightly may give
a "scrubbing" feel like rubbing up against a curb (only
not as pronounced). Vehicles experiencing this
condition can feel “pulled” in both directions depending
on the positions of the tires in the trough (ruts).
Driving Characteristics
A test drive with the customer to duplicate the concern
and driving a comparably equipped vehicle over the
same roads may be beneficial before any repairs are
attempted. For further information on diagnosing
vehicle leads/pull issues, refer to the latest version of
Corporate Service Bulletin #05-03-07-009.
Note: Test driving over road surfaces, like smooth
concrete, the vehicle may be less susceptible to
pavement inconsistencies due to the fact that concrete
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can be less susceptible to developing troughs and
other variations in the road surface. Additionally, since
troughs may or may not be visible in a given lane, it is
recommended to drive the vehicle within the lane, but
on each side of the lane to verify if the vehicle is
reacting to the road surface variation due to the
steering precision of vehicles in this category.
If a similarly equipped vehicle experiences the same
condition as the customer’s car, the customer’s car is
most likely experiencing tramlining, which is a normal
characteristic of a car with low aspect ratio, wide tires.
Tires
Verify that all tire pressures are set to the specification
listed on the vehicle’s tire placard prior to driving and
verify there is no uneven tire wear.
Note: Tire pressures should be maintained at the
recommended pressures. Increasing tire pressures
above the recommended pressure will further stiffen the
sidewall of the tire and may increase tramlining.
Swapping tires from a known good vehicle can be used
to determine if the condition is tire related.
Verify that the tires and suspension setting have not
been modified from the production standards. GM
accessory wheels and tires are an acceptable
modification.
Page 2
May, 2021
Bulletin No.: 17-NA-087
Alignment
While alignment may be thought to be a contributing
factor, it has NOT been found to affect trough wander or
tramlining complaints and therefore a wheel alignment
check is NOT recommended for the condition.
Reference the latest version of Corporate Service
Bulletin #05-03-07-009 for GM Corporate policy
information on wheel alignment.
Version
5
Modified
Released March 21, 2017
March 15, 2019 – Added the 2018 and 2019 Model Years.
January 31, 2020 – Added the 2020 Camaro Model and updated the Involved Regions or
Country section.
October 12, 2020 – Added 2020 Corvette and 2021 Camaro and updated the Involved
Region or Country section.
May 05, 2021 – Added the 2020–2021 CT4 and CT5 models and the 2021 Corvette.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a
job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.
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