Tire and Wheel Rotational Speed Calculation

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

A size P235/75R15 tire rotates ONE complete revolution per second (RPS), or 1 Hz, at a vehicle speed of 8 km/h (5 mph). This means that at 16 km/h (10 mph), the same tire will make TWO complete revolutions in one second, 2 Hz, and so on.

Tire Rotational Speed (at 8 km/h [5 mph])

Tire Size	Tread	Revs/Sec (Hertz) at 8 km/h (5 mph)
LT215/85R16	ALS HWY OOR	0.95
P235/75R16	ALS	0.96
LT245/75R16	OOR	0.94
P245/75R16	ALS AT	0.95 0.94
LT255/75R16	ALS	0.93
P255/70R16	ALS	0.96
LT265/75R16	OOR	0.90
P265/70R16	AL2	0.94
P265/75R16	AT	0.91
P265/70R17	AL2	0.91
Tread Codes
ALS		All Season
AL2		All Season Touring
AT		All Terrain Light Truck
HWY		Highway
OOR		On-Off Road

Determine the rotational speed of the tires in revolutions per second (RPS), or Hertz (Hz), at 8 km/h (5 mph), based on the size of the tires. Refer to the preceding Tire Rotational Speed table.
For example: According to the Tire Rotational Speed table, a P255/70R16 tire makes 0.96 revolutions per second (Hz) at a vehicle speed of 8 km/h (5 mph). This means that for every increment of 8 km/h (5 mph) in vehicle speed, the tire's rotation increases by 0.96 revolutions per second (Hz).
Determine the number of increments of 8 km/h (5 mph) that are present, based on the vehicle speed (km/h, mph) at which the disturbance occurs.
For example: Assume that a disturbance occurs at a vehicle speed of 96 km/h (60 mph). A speed of 96 km/h (60 mph) has 12 INCREMENTS of 8 km/h (5 mph):

96 km/h (60 mph) divided by 8 km/h (5 mph) = 12 increments
Determine the rotational speed of the tires in revolutions per second (Hz), at the specific vehicle speed (km/h, mph) at which the disturbance occurs.
For example: To determine the tire rotational speed at 96 km/h (60 mph), multiply the number of increments of 8 km/h (5 mph) by the revolutions per second (Hz) for one increment:

12 (increments) X 0.96 Hz = 11.52 Hz (rounded to 12 Hz)
Compare the rotational speed of the tires at the specific vehicle speed at which the disturbance occurs, to the dominant frequency recorded on the J 38792-A during testing. See Special Tools and Equipment . If the frequencies match, then a first-order disturbance related to the rotation of the tire/wheel assemblies is present.
If the frequencies do not match, then the disturbance may be related to a higher order of tire/wheel assembly rotation.
To compute higher order tire/wheel assembly rotation related disturbances, multiply the rotational speed of the tires at the specific vehicle speed at which the disturbance occurs, by the order number:
12 Hz X 2 (for second order) = 24 Hz second-order tire/wheel assembly rotation related

12 Hz X 3 (for third order) = 36 Hz third-order tire/wheel assembly rotation related

If any of these computations match the frequency of the disturbance, a disturbance of that particular order, relating to the rotation of the tire/wheel assemblies is present.