 This is Mr. Nagesh Arthambake, Assistant Professor, Mechanical Engineering Department, Valchan Institute of Technology, Sholapur. Today, we are going to discuss the automobile steering geometry, learning outcome. At the end of this session, students will be able to explain automobile steering geometry. In this particular session, we are going to discuss what is steering geometry and different types of steering geometries. Now, before discussing this topic, we will see what is meant by automobile steering geometry. Please think, students, what is steering geometry. We will see, it is the relationship of the angles among the front wheels, front wheel attaching parts and ground. First one, the steering geometry is the camber. Camber is the inward or outward tilt of wheels from vertical when viewed from the front of the vehicle. Camber is measured in degrees on vehicle, positive camber is adjusted initially. So, when vehicle is loaded and rolling along the road surface, vehicle should run straight up and down with zero camber. This puts the full width of the tyre trade on the road surface, which is desirable. However, it is difficult to obtain a zero camber. The camber goes negative when tyre hits the bump and goes positive when falls in a pothole. This is caused by unequal length control arms of the suspension system. In any camber, either positive or negative causes uneven tyre wear. So ideally, camber should be zero, which is somewhat difficult. So initially, negative camber is provided. Now, next one is caster. What is meant by caster? It is the tilt of steering axis towards the front or rear of the vehicle. If the tilt is towards the front, it is taken as negative and when it is towards the rear, taken as positive. Usually, positive caster is provided to the vehicle. Caster is measured in degrees. Caster angle adjustment is for some feasibility. So, first one is to maintain directional stability and control to increase steering returnability and to reuse steering effort. This requirement can be met by providing positive caster. Vehicles with power steering have more positive caster than with manual steering. However, the more positive caster requires more steering effort, which is not filled due to power steering. Any degrees in positive caster then require causes spring sagging. Next one, that is steering axis inclination. That is also called as kingpin inclination. First of all, we will see what is steering axis. It is the line passing through centers of ball joints. It is the axis around which a front wheel swings for steering. It is the angle between vertical line and steering axis. It is the inverted of the steering axis from vertical as viewed from the front. This inverted is desirable because of some of the reason. It helps in returning the steering wheel to straight ahead after completing a turn and keeps the vehicle in stable condition. This is called as steering returnability. It helps in reducing steering effort, especially when vehicle is not moving and also reduces tire wear. Steering axis inclination cannot be adjusted because it depends on geometry of knuckle. Usually it is correct, but when it is not within the specification, the spindle, steering knuckle, ball joint and other dependent parts wear or bend down. This is indication of a wrong steering axis inclination. In this, we will see what is scrub radius. In this particular figure, we have shown a distance between this particular ball joint and the tire. That will give you a scrub radius. The term scrub radius is defined as it is the distance between steering axis and tire contact area centerline as their intersection with road surface. If the steering axis intersects the road surface inside the tire centerline, scrub radius is positive. If that intersection point is outside the centerline of the tire, it is negative. Zero scrub radius means steering axis and tire axis meet at ground surface exactly. Scrub radius is not an alignment angle and usually cannot be directly measured. However, it directly affects steering stability. Steering effort and steering return ability rear drive vehicles with unequal length front suspension control arm often have positive scrub radius. While front drive vehicles with macpherson strut from suspension have negative scrub radius. Next one, that is tow in, tow out. What is tow in, tow out? It is the measurement of how much the wheels point in or out from the straight ahead position. It is measured in mm, inches or in degrees. Ideally, running tow must be zero. When the wheel points inwards, it is tow in. And when wheel points outwards, it is tow out. Zero tow means the wheels run parallel. They are at same distance part at in front as well as in rear. Any tow in or tow out tracks the tire sideways as it rolls. The greater the tow angle, faster the tire rear. Next one we will see. In this also we will discuss the suspension height. That is not mentioned over here. What is suspension height? It is the distance measured from some specific point of the body frame or suspension to the ground. It is not adjusted correctly. It can affect wheel alignment. Incorrect height can affect from sagging coil or leaf spring. Incorrect torsion bar adjustment. Now next one we will see that is the turning radius. What is turning radius? It is the difference in the angles of the front wheels in turn. Also called as tow out on turn or turning angle. During a turn, the two front wheels travel on concentric circles. Having common centers, the inner wheel run through greater angle while outer run through a smaller one. So as the distance is greater from outer wheel and small for inner wheel. If turning radius is incorrect, check for the bent in steering arm or a tire rod. Now next one is the included angle. Included angle, it is the addition of camber angle and steering axis inclination. Together it will form an included angle. It is not an adjustable angle. However, an improper included angle often indicates a bent in spindle or strut. Now next one is setback. What is setback? Wheel setback is the difference in vehicle wheelbase from one side to other. It occurs when one wheel is behind the other on same axle. Setback occurs from production tolerances during vehicle manufacturing or from impact damage. It also occurs because of improper placement of engine or subframe. A vehicle with drift or pull towards the side with shorter wheelbase setback more than 19 mm is excessive indicates bent in parts. Now last one is that is the thrust angle. Here you can see in this figure what is the thrust angle. When the wheel is properly aligned, it should move in a straight line. But if rear of vehicle has improper setback, it may not move straight ahead. The direction of travel is determined by three lines. That is run the length of vehicle. Vehicle center line is the line passing through center of the vehicle body. This line should be the same as the geometric center line of the vehicle that connects the midpoints of front wheels and rear wheels. The thrust line is a line from the midpoint between the two rear wheels. Now these are the references. Thank you.