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 Size | Tread | Revs/Sec (Hertz) at 8 km/h (5 mph) |
---|---|---|
P205/75R15 | ALS | 1.06 |
P235/55R16 | AL2 | 1.07 |
P235/70R15 | ALS | 1.03 |
P235/75R15 | ALS | 1.00 |
31X10.50R15LT/C | OOR | 0.95 |
Tread Codes | ||
ALS | All Season | |
AL2 | All Season Touring | |
OOR | On/Off Road |
For example: According to the Tire Rotational Speed table, a P235/70R15 tire makes 1.03 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 1.03 revolutions per second (Hz).
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
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 1.03 Hz = 12.36 Hz (rounded to 12 Hz)
If the frequencies do not match, then the disturbance may be related to a higher order of tire/wheel assembly rotation.
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.
12 Hz X 3.42 drive axle (final drive) ratio = 41.04 Hz (rounded to 41 Hz) first-order propeller shaft rotation related
If the frequencies do not match, then the disturbance may be related to the second-order of propeller shaft rotation.
41 Hz X 2 (for second order) = 82 Hz second-order propeller shaft rotation related
If the computation matches the frequency of the disturbance, a disturbance relating to the second-order rotation of the propeller shaft is present.
Utilize the following worksheet as an aid in calculating the first, second and third order of tire/wheel assembly rotational speed and the first and second order of propeller shaft rotational speed related disturbances that may be present in the vehicle.
If after completing the Tire/Wheel Rotation Worksheet, the frequencies calculated do NOT match the dominant frequency of the disturbance recorded during testing, either recheck the data, or attempt to rematch the figures allowing for 1½-8 km/h (1-5 mph) of speedometer error.
If the possible tire/wheel assembly and/or propeller shaft rotational speed related frequencies still do not match the dominant frequency of the disturbance, the disturbance is most likely torque/load sensitive.
If after completing the Tire/Wheel Rotation Worksheet, one of the frequencies calculated DOES match the dominant frequency of the disturbance, the disturbance is related to the rotation of that component group, (tire/wheel assembly or propeller shaft).