... Derivation of the radius of an arc-chord formula on Math Open Reference in case you really want to know where this formula … // --> GD&T Training Geometric Dimensioning Tolerancing This will affect how the tire contact patch interacts with the road during cornering, braking, and acceleration, and can cause unique toe characteristics depending on the design. Scrub radius is the distance between the steering axis ( at ground level ) and the center line of the tire. The scrub radius can affect the way the steering responds in both a straight line and during cornering. } When viewing a wheel from front view, the scrub radius is the distance between where the extrapolated line of kingpin axis touches the road and the tyre contact patch centre point. Positive Scrub Radius Lines Meet Below Road Surface Usually Rear Wheel Drive With Front Wheel Toe In; SAI Usually Less Than 10 Degrees; Negative Scrub Radius. Your email address will not be published. Automotive Videos. Disclaimer rs = Turning circule radius (mm) document.write('') One last consideration in the steering design is scrub radius. Fig.5 Trackwidth Geometry Note: Generally narrow (small) trackwidth are used at rear to avoid hit cones with the back when they are Suspension geometry is a mixture of theoretical lines designed into a suspension system to make it work in a particular designed way. In a car with zero scrub radius the tire pivots around a central axis without dragging the tire forward or rearward. Notify me of follow-up comments by email. Engineering News Training Online Engineering A positive radius allows the wheel to roll over on lock making parking situations easier. Keywords: KPI, Camber, Caster, Scrub Radius, Roll Centre, Instantaneous Centre. 1 We must look at it in three ways. Online Books & Manuals Advertising Center Wheel-Size.com is a Wheel Guide and catalogue. In addition, while the vehicle is moving dynamic forces will arise that will affect the cornering maneuver. Scrub radius is the distance at the road surface between the tire line and the steering axis inclination (SAI) line extended downward through the steering axis. If the extrapolated KPI is outboard of the contact patch then the scrub radius is negative. Scrub Radius, Kingpin Inclination, and Caster. About us. A, how it affect the driving, B, cornering capacity, C, the geometric effect. With any kingpin angle, steering will tend to raise and lower the vehicle. Draw an imaginary line to the ground through the kingpin screws and ideally that imaginary line lands close to the center of the tire to achieve the ideal scrub radius. scrub radius, mechanical trail etc. Scrub radius is considered positive when I have reached out recently to "Ford Performance", as well as Dean Martin of KOHR Racing on the exact scrub radius numbers. ro = Scrub radius (mm) the distance in front view between the king pin axis and the center of the contact patch of the wheel, where both would theoretically touch the road. Tyre Failure – Graining, Tearing, Blistering and Wearing, Tyre Performance and Grip – A Deeper Look, Calculating Ideal Spring and Roll Bar Rates, Calculating Ideal Spring and Roll Bar Rates Part 2. Enter your email address to subscribe to this blog and receive notifications of new posts by email. { Scrub Radius. document.write(''); }, Power Transmission Design and Engineering The three possible geometries that can be used are Ackermann, anti-Ackermann and parallel steer geometry. Wheel you get tire pivots around a central axis without dragging the tire pivots a. These values has to be kept in mind while designing, the major factor the! Radius allows the wheel you get a vehicle is moving dynamic forces arise... This blog and receive notifications of new posts by email is small then the scrub radius tends be! Three ways on Twitter ( Opens in new window ) for the steering axis ( at ground level ) the! Subject of interest and pinion connects the tie rods to the scrub radius is the type geometry... Refers to the steering gear and linkage or rack can have a effect! Using Lotus you should know your Track-width and front Dimension of your car can be altered with different offset. 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