Scrub radius is the distance between where the SAI intersects the ground and the center of the tire. Its aspect, pressure and rim width sensitive, but … Reason is that tire brand specific properties introduce a dynamic scrub radius effect. A negative scrub radius tends to better for braking stability in the event of brake failure or split-mu braking. 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. A scrub radius is the distance between where the wheel's steering axis meets the ground and where the wheel's centerline meets the ground, as viewed from the front of the vehicle. II. Modern passenger cars use a scrub radius of the order of 0.25" to 0.75", either negative or positive. The kingpin axis is the line between the upper and lower ball joints of the hub. However by using 10.5" CCW wheels with the allowable SCCA 0.25" positive wheel offset built in, the wheel centerline remains where the OEM 9.5" 's is and the Zero scrub radius is retained. At Low Speeds or Parking Maneuvers At High Speeds Why Scrub should be –ve under Braking – esp. Required fields are marked *. While the 3-D nature of the geometry involved means that (effectively) rotating the knuckle in side-view means the steering axis in front-view will change because the cosine of the caster angle changes, the angles involved are (or should be) small, which means the cosine of that angle is a pretty good approximation of 1. Why FWD vehicles go for +ve Scrub? Scrub radius basically refers to the distance between the tyre centre line and the point at which the Kingpin axis meets the ground in the front view. Your email address will not be published. The main effect of this is to introduce a turning moment. Well, scrub radius doesn't change with the camber plate or lower control arms. Different wheels or DESIGN While designing, the major factor is the type of geometry to be used for the steering system. This distance must be exactly the same from side to side or the vehicle will pull strongly at all speeds. NOTE: Scrub Radius is defined as the point of intersection of the king pin angle (a line drawn through the upper and lower ball joints and the mid line plane (steering plane) of the wheel (tire). If the scrub radius is small then the contact patch is spun in place when parking, which takes a lot more effort. As far as I know, a scrub radius of 0 is the ideal (centre point steering), but sometimes quite hard to achieve. Scrub Radius,, I have read and reread JH handling issues---I have a lakester which now has Postive Scrub radius of several inches 39 Chevy 6X 5.5" hubs and 15"wheels with 21" Goodyears---for several reason I would like to move this to at least 0 if not some neg. Scrub Radius is defined as the distance between the intersection of the steering access and the ground measured to the center of the contact patch, viewed perpendicular to the vertical- lateral plane. SAI is an imaginary line, that on strut suspensions runs through the lower ball joints and the upper end of the strut. Questions: Why an increasing Scrub radius is always associated with increasing steering effort and returnability? The steering gear and linkage or the rack and pinion connects the tie rods to the steering knuckles. It only changes between the strut and the wheel. A positive radius allows the wheel to roll over on lock making parking situations easier. 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. The fundamental categories of suspension geometry are: Ackermann Bump Steer Camber Camber Gain Caster Front View Swing Arm Fundamentals of Grip Instantaneous Centre King Pin Inclination Scrub Radius Toe Tyre Slip Angle There are more aspects to suspension geometry but the most influential are listed above and are the focus of this website. Verify the method by simulate The inclination of the … On a MacPherson strut, the top pivot point is the strut bearing, and the bottom point is the lower ball joint. A negative scrub radius gives a harder feel to the steering wheel as it requires more input to turn. A new wheel end concept was designed and developed to allow sport utility vehicles (SUV) and light trucks the possibility of achieving a negative scrub radius. Advertisement. Click to share on Twitter (Opens in new window), Click to share on Facebook (Opens in new window). The three possible geometries that can be used are Ackermann, anti-Ackermann and parallel steer geometry. What Is Scrub Radius? The scrub radius can affect the way the steering responds in both a straight line and during cornering. This distance must be exactly the same from side to side or the vehicle will pull strongly at all speeds. http://www.theaudiopedia.com What is SCRUB RADIUS? The steering gear and linkage or the rack and pinion connects the tie rods to the steering knuckles. The location of the steering gear linkage or rack can have a … What does SCRUB RADIUS mean? have to be kept in mind while designing and the best compromise for these values has to be found. mike mendoza. Some rwd cars actually can get negative scrub even though they may have positive scrub radius with geometry. 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. Author Topic: Scrub Radius (Read 23787 times) 0 Members and 1 Guest are viewing this topic. Positive scrub radius is defined as the steering axis intersecting the ground plane between the vehicle centerline and the contact patch. Posted 29 April 2006 - 07:42. Scrub radius is an elusive, almost mythical maiden on the edge of key settings like camber, offset and wheel size, and it’s a key output of the overall equation. A four in-wheel-motor drive electric vehicle has four independent steering and independent suspension.This paper is to present a novel design of an independent suspension to reduce the uneven tire wear caused by scrub radius based on those independent suspension . Scrub radius is the distance shown in the diagram in post #4. Notify me of follow-up comments by email. Section "Scrub radius" inside article "Scrub radius" Two issues: 1. The biggest effect is called bump steer. It also reduces the risk, that a lose of traction on one front wheel during braking, causes the car to change direction. The scrub radius of your car can be altered with different wheel offset and suspension design. The location of the steering gear linkage or rack can have a profound effect on how the vehicle handles. The scrub radius is 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. with ABS? 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. Related Videos:Toe-in vs Toe-out - https://youtu.be/83_GTZeuF6MSteering Axis Inclination - https://youtu.be/IUcZ63unEyUCaster - https://youtu.be/Gh7gWJAvOvsCamber - https://youtu.be/jSFmUmVWBp0Please feel free to rate, comment, and subscribe!And don't forget to check out my other pages below!Facebook: http://www.facebook.com/engineeringexplainedOfficial Website: http://www.howdoesacarwork.comTwitter: http://www.twitter.com/jasonfenske13Instagram: http://www.instagram.com/engineeringexplainedCar Throttle: https://www.carthrottle.com/user/engineeringexplainedTo help create more videos, check out my Patreon page!http://www.patreon.com/engineeringexplainedNEW VIDEO EVERY WEDNESDAY! Build a virtual model of the novel suspension in ADAMS and simulate. The thing is, I know this will alter the scrub radius (beside other things like bearing load, etc) and after reading something about this I didn't came to a certain conclusion regarding how this will affect the handling of a clio (182 cup suspension with 16" ET 37 wheels I … The scrub radius can affect the way the steering responds in both a straight line and during cornering. As soon as I got my lift, I headed straight to NTB to get an alignment and the result was a caster measurement of 4.5 on the left and 2.8 on the right, with the right side being out of spec. Enter your email address to subscribe to this blog and receive notifications of new posts by email. It can go both ways. scrub radius, mechanical trail etc. This paper will compare a production vehicle with a scrub radius of 54.8 mm with the same vehicle modified with several alternate scrub radi There's a poorly-named section (same name as the article itself) 2. Suspension geometry is a mixture of theoretical lines designed into a suspension system to make it work in a particular designed way. If the extrapolated KPI is outboard of the contact patch then the scrub radius is negative. Budget to Premium Coilovers – Whats The Real Difference? On our spindle type front suspension, then you can only change it by changing either the hub offset or wheel offset. I have a 2.75" lift on the front of my 2014 access cab with 265/60/18 wheels. The scrub radius is the distance in front view between the Steering Axis and the center of the contact patch where both would theoretically touch the road. It could be positive, negative or zero. The steering axis is the line between the top pivot point of the hub and the lower ball joint of the hub. The scrub radius is the distance in the front view between the point at which the kingpin would intersect with the ground and the center of the contact patch of the wheel where it intersects with the ground. While included angle problems will affect the scrub radius, it is not the only thing that will affect it. Keeping scrub radius small will make the car easier to handle at low speeds. Guidelines to design scrub radius – Direction and Magnitude? 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. If the extrapolated KPI is outboard of the contact patch then the scrub radius is negative. The parameters obtained from this axis are described in an earlier post. The kingpin inclination also contributes to the scrub radius of the steered wheel, the distance between the centre of the tyre contact patch and where the kingpin axis intersects the ground. While included angle problems will affect the scrub radius, it … First, let's start by looking at the suspension movement and the tools available to make your life easier: The chassis movement control allows you to raise and lower the chassis and also rotate the chassis by moving the mouse (or your finger) side to side. - posted in The Technical Forum Archive: Hi Chaps, can I ask a question please. Save my name, email, and website in this browser for the next time I comment. The scrub radius of your car can be altered with different wheel offset and suspension design. The caster is a side-view issue. A positive scrub radius tends to be beneficial while braking into a turn. Scott tomeric914. The scrub radius is a front-view issue. If it is inboard then the scrub radius is positive. Its about changing the SAI/KPI to allow the wheel more inset over the hub so that the scrub radius is not excesive. Mit Flexionstabellen der verschiedenen Fälle und Zeiten Aussprache und … Dallara World Series Single Seater – Under The Skin, Coilovers – Installing and Setting Ride Height Correctly, Helper Springs and Tender Springs – The Difference, https://www.youtube.com/watch?v=_Ksbfn40adA. Some material in that section is redundant, but some of it conflicts with the rest of the article. If you had the 2 bolts on the knuckle that bolt to the strut, then you can change the scrub radius. Scrub radius is explained in this article - What is Scrub Radius : Sharing: Instructions. Having a small scrub radius is beneficial as it allows the wheel to react less to braking inputs due to the smaller moment arm and increases steering stability under braking conditions. Older cars used a scrub radius of up to 4 inches, positive. QUOTE(SirAndy @ May 24 2013, 04:52 PM) Whatever you use, make sure your front wheels are as close to the strut as possible without rubbing on the strut or fender. If it is inboard then the scrub radius is positive. The inclination of the KP axis in the side view is caster. Page 1 of 2 - SCRUB RADIUS. Typically the scrub radius is configured to be as small as possible to minimize the effects under braking, but squirm (from zero scrub radius) is also undesirable. Lernen Sie die Übersetzung für 'scrub radius' in LEOs Englisch ⇔ Deutsch Wörterbuch. I wonder if any one would have any thoughts on a problem I have. It generates a slight toe-in force that reduces any tendency to change direction in the way that positive scrub radius can allow. Scrub Radius Scrub radius is the distance between where the SAI intersects the ground and the center of the tire. Your email address will not be published. On a MacPherson strut, the top pivot point is the strut bearing, and the bottom point is the lower ball joint. Answers: In the event… In this part of the suspension basics miniseries, I talk about scrub radius, what it is and why it's important. 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