Tire axis system and terminology defined by SAE standards which defines the tire axis system and terminology is SAE J – Vehicle Dynamics Terminology. Slip ratio is a means of calculating and expressing the slipping behavior of the wheel of an The SAE J definition is, for tires pointing straight ahead: S l i p R. 15 Dec standard published by SAE International (SAE JJAN). This revision extends the scope to include provision for separate tyre and wheel.

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Race Car Vehicle Dynamics.

The positive direction of the x-axis j6700 pointing towards the front of the vehicle. The normal force F z is the force applied by the road to the wheel.

Tire axis system and terminology defined by SAE standards

Furthermore, it is essential to the effectiveness of any anti-lock braking system. This slippage is caused by the forces at the swe patch of the tire, not the opposite way, and is thus of fundamental importance to determine the accelerations a vehicle can produce. This page was last edited on 26 Septemberat From Wikipedia, the free encyclopedia.

This article is about tire behavior in vehicle dynamics. It is of fundamental importance in the field of vehicle eae, as it allows to understand the relationship between the deformation of the tire and the longitudinal forces i.

The aligning torque moment M z is the torque which rotates the wheel around the z-axis. It is only relevant in soft or slippery surfaces, like snow, mud, ice, etc and results constant speed difference in same road and load conditions independently of speed, and thus fraction of slip ratio due to that cause is inversely related to speed of the vehicle. The z-axis is normal to the road, the positive direction being downwards.


The dynamic performance of a road vehicle depends largely by the characteristics of the tire. It is negative pointing upwards and positive pointing downwards. The overturning torque moment M x is saae torque which is trying to rotate the wheel around the x-axis the wheel is falling over.

Slip ratio – Wikipedia

The origin O is the sea of intersection of x,y and z axes. When accelerating or braking a vehicle equipped with tires, the observed angular velocity of the tire does not match the expected velocity for pure rolling motion, which means there appears to be apparent sliding between outer surface of the rim and the road in addition to rolling due to deformation of the part of tire above the area in contact with the road.

For the forces and torques action on the wheel, we will define which is the positive direction. By using this site, you agree to the Terms of Use and Privacy Sxe. Vehicle braking technologies Engineering ratios.

The y-axis is perpendicular on the x-axis and the positive direction is pointing to the right side of the wheel. When driving on dry pavement the fraction of slip that is caused by actual sliding taking place between road and tire contact patch is negligible in magnitude and thus does not in practice make slip ratio dependent on speed. The torque generated by the powertrain is applied at the wheel through the tire.


The rolling resistance torque moment M y is the torque which opposes the wheel to turn around the y-axis. On front-wheel drive FWD vehicles there is an additional torque, the drive torque.

Views Read Edit View history. The origin O of the axis system it is located in the center of the contact patch. H670 from ” https: Slip ratio is a means of calculating and expressing the slipping behavior of the wheel of an automobile. The surface of contact between the tire and the road is called contact patch. Society of Automotive Engineers.

When the aae is inflated, the weight of the vehicle applies a normal vertical load on the wheel which causes the deflection of the tire.

Slip ratio

J70 lateral force F y is positive towards the right, when the vehicle is moving forwards along the x-axis. There is no universally agreed upon definition of slip ratio. For the phenomenon in fluid dynamics, see Slip ratio gas-liquid flow.

In order to be able to analyze the forces and moments which are acting on a vehicle tire, especially during cornering, we need to define an axis coordinate system.

All three axes are mutually orthogonalwhich means that they are perpendicular to each other.