Steering Geometry Terms Used

Welcome Please log onto a PC and then sit back in the middle.

Objectives; At the end of this lesson you will able to: Identify the terms used in relationship to steering geometry. Describe the Ackerman principal. Describe over steer and under steer.

Wheel base and track Describe track. This is the distance between the wheel centres of the wheels on the same axle. Describe wheelbase. This is the distance between the wheel centres of the front and rear wheels

Describe camber angle This is the angle between the wheel plane and a line perpendicular to the road surface. It is described as positive if the wheel is inclined out at the top and it is described as negative if the wheel is inclined in towards the centre line of the vehicle at the top   What is the purpose of camber angle? Correct camber (along with toe and caster) makes sure that the tyre tread surface is as flat as possible on the road surface.

Castor angle

Describe castor angle For this angle, the theoretical driving point is slightly ahead of the tyre contact point which, due to tyre drag, tends to follow. What is the purpose of castor angle? This angle aides self centring Enables the driver to “feel” the straight ahead position.

Toe out and toe in

Describe toe in/toe out This term is given to the left-right alignment of the front wheels relative to each other. When it is said to be in, the front edge of the wheels is closer together than the rear, and it is out when the rear edge is closer than the front. What is the purpose of toe in/toe out? To minimize tyre wear and power loss, the wheels on a given axle of a car should point directly ahead when the car is moving in a straight line.

King pin inclination or swivel axis inclination (SAI) When the steering wheel is turned, SAI has the effect of lifting the front of the vehicle slightly so when the steering wheel is released, the weight of the vehicle forces the wheels back to the straight ahead position.

Scrub radius Scrub radius is the distance between the contact point of the steering axis with the road and the centre line of the wheel.

The Ackerman principle. The Ackerman Steering Principle describes the relationship between the front wheels of a vehicle as they relate to each other when cornering

Ackerman principle

Ackerman principle

Ackerman principle

Ackerman principle. To create the Ackerman steering principle, the steering arms are angled to turn the inside wheel at a sharper angle than the outside wheel. This allows the inside wheel to follow a smaller radius circle than the outside wheel.

true Ackerman angle.

more Ackerman angle.

less Ackerman angle.

Objectives; At the end of this lesson you will able to: Identify the terms used in relationship to steering geometry. Describe the Ackerman principal. Describe over steer and under steer.