ATTENTION:
GENERAL MANAGER

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PARTS MANAGER

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CLAIMS PERSONNEL

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IMPORTANT - All
Service Personnel
Should Read and
Initial in the boxes
provided, right.

SERVICE MANAGER

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© 2025 Subaru of America, Inc. All rights reserved.

SERVICE INFORMATION BULLETIN
APPLICABILITY: All Models
SUBJECT: Vibration During High Speeds / Diagnosis

NUMBER: 05-97-26
DATE:

04/20/26

This Service Information Bulletin provides the diagnostic procedures to be followed when addressing
customer concerns of steering wheel/vehicle body vibration when driving at highway speeds when
tire/wheel balance is suspected. The bulk of these concerns can be generally addressed using proper
wheel balancing and road force matching. This bulletin outlines additional diagnostic information to
provide a precise vibration source identification.
SERVICE INFORMATION:
WHEEL IMBALANCE: Wheel imbalance is caused by uneven mass distribution in the tire and
wheel assembly. This condition can generate vibration due to centrifugal force during rotation.
Because wheel imbalance is the most common cause of steering wheel or vehicle body vibration, it
should be addressed first during diagnosis.
The two most common types of wheel imbalance are static (single-weight plane) and dynamic
(dual-weight plane). Static imbalance is best described as a vertical imbalance when the assembly is
mounted on the vehicle. Dynamic imbalance is defined as a combination of vertical and inner/outer
imbalance when the assembly is mounted on the vehicle.
To achieve the best possible results, a well-maintained dual-weight plane balancer (commonly known
as a dynamic balancer) should be used.
RADIAL FORCE VARIATION (RFV): Radial Force Variation (RFV) is the periodic change
in load (force) occurring in the radial direction (up and down) as the tire rotates. It is caused by
variations in tire roundness and stiffness and is a primary contributor to vibration during vehicle
operation.
A dynamic balancer measures these variations and displays them as R1H (radial first harmonic), R2H
(radial second harmonic), and R3H (radial third harmonic). In most cases, the first harmonic (R1H) is
the primary cause of steering wheel or vehicle body vibrations occuring at highway speeds.
Radial Force Variation can increase if a vehicle has been parked for an extended period, which may
create temporary flat spots in the tires. Improper tire inflation can also contribute to increased RFV.
CAUTION: VEHICLE SERVICING PERFORMED BY UNTRAINED PERSONS COULD
RESULT IN SERIOUS INJURY TO THOSE PERSONS OR TO OTHERS.
Subaru Service Bulletins are intended for use by professional technicians ONLY. They
are written to inform those technicians of conditions that may occur in some vehicles,
or to provide information that could assist in the proper servicing of the vehicle. Properly
trained technicians have the equipment, tools, safety instructions, and know-how to
do the job correctly and safely. If a condition is described, DO NOT assume that this
Service Bulletin applies to your vehicle, or that your vehicle will have that condition.

Subaru of America, Inc. is
ISO 14001 Compliant
ISO 14001 is the international standard for
excellence in Environmental Management
Systems. Please recycle or dispose of
automotive products in a manner that is friendly
to our environment and in accordance with all
local, state and federal laws and regulations.

Continued...
Bulletin Number: 05-97-26; Date: 04/20/26

Page 1 of 6

SERVICE PROCEDURE / INFORMATION:
STEP 1: Vehicle Check and Test Drive
•

Inspect tires and wheels for any visible
damage.

•

If any damage is found, resolve these
concerns before continuing with diagnosis.

•

Adjust tire pressures according to the door
label.

•

Test drive to confirm the customer’s
concern. If the vibrationis confirmed, go to
Step 2.

STEP 2: Measure Wheel Balancing and
Adjustment
•

Perform a balance test. Record the results
and positioning. If the result is within 5
grams, go to Step 3.

•

If the result is 5 grams and higher, adjust
it within 5 grams. Leave any remaining
factory weights in place and remove
weights that have been added after
production.

CAUTION: Be careful not to damage the wheel when removing weight.
•

In cases of the wheel/tire assembly cannot be adjusted within 5g (0.18oz) or less, inspect for the
following:
Improperly mounted tire such as an unseated tire bead
Improperly mounted wheel/tire assembly to the balancer
Damage to the wheel or tire
Damage to the tire balancer
Debris located inside the tire

NOTES:
•

Tire weights after adjusting the wheel balance should be 5g (0.18oz) or less.

•

When using adhesive weights, thoroughly degrease the surface where the weight is to be applied.

•

After applying the adhesive weight, apply force to the weight to attain full adhesion.

•

When using clip-on weights, check and confirm the correct clip size (5mm (0.2in)).
Continued...

Bulletin Number: 05-97-26; Date: 04/20/26

Page 2 of 6

STEP 3: Test Drive after Wheel Balance Adjustment
Test drive the vehicle after wheel balance adjustment.
•

If the vibration is gone, finish the repair. (The cause of the vibration was improperly adjusted
wheel balancing.)

•

If the vibration still exists, keep driving at highway speed for 15 miles (24 kilometers). Stop
driving if the vibration is gone.

•

If the vibration still exists after 15 miles of driving, keep driving the vehicle until the vibration
is gone or for a total of 80 miles. (Approximate 80 miles (128 kilometers). Stop driving if the
vibration is gone. (The cause of the vibration was the tire flat spot.) Additional information
regarding flat spots is listed below.

NOTE: The road is to be completed in one single drive.
•

If the vibration still exists, go to Step 4.

TIRE FLAT SPOTS:
Tire flat spots are caused by long-term
transport or storage. This is a temporary
condition. In most cases, the flat spot can be
eliminated by driving. To eliminate flat spots,
it is effective to continue driving at highway
speed whilst the tires are warm. Additionally,
repeatedly changing lanes within safe limits
is also effective. The tire flat spots may not
be eliminated in winter because the tire
temperature is very difficult to rise due to the
low ambient temperature.

TIP: When possible, lift the vehicle within ten minutes after road testing to cool down the tire
surface to ambient room temperature. Flat spots are easily formed during long-term vehicle storage in
room temperature areas or after driving with the tires at high temperatures. Keeping the vehicle lifted
during tire cool down is recommended.

Continued...
Bulletin Number: 05-97-26; Date: 04/20/26

Page 3 of 6

STEP 4: Radial Force Variation (RFV) Measurement
If vibration can still be felt after the wheels have been properly balanced and 80 miles driving, there
is a possibility of excessive radial force variation (RFV) in the tire and wheel assembly. Please
perform the following:
NOTE: In this case, tires can be removed from the vehicle right away after driving. Cooling time is
not required.
•

Measure the RFV of the four tire and wheel assemblies. RFV measurements for passenger tires:
8.0kg (18lbs 80N) or less.

•

If higher than normal RFV measurements are found for the assembly, refer to the on-screen
instructions or the operating instructions to “match mount” the tire and wheel to minimize the
assembly RFV.

•

After all RFV measurements are adjusted to the lowest possible level, relocate the tires and
wheels as the following.

•

After relocating the tires and wheels, perform a road test to verify the concern has been resolved.

•

If the concern still exists at an unacceptable level, contact the Subaru Techline with the data sheet
located on the next page.

Continued...
Bulletin Number: 05-97-26; Date: 04/20/26

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Continued...
Bulletin Number: 05-97-26; Date: 04/20/26

Page 5 of 6

IMPORTANT REMINDERS:
•

SOA strongly discourages the printing and/or local storage of service information as previously
released information and electronic publications may be updated at any time.

•

Always check for any open recalls or campaigns anytime a vehicle is in for servicing.

•

Always refer to STIS for the latest service information before performing any repairs.

Bulletin Number: 05-97-26; Date: 04/20/26

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