This is not the best thing to do as too much rear toe-in will cause your car to instantly straighten up mid-drift if you let go of the throttle. A loss of traction can cause that when you brake. Keywords: Vehicle Dynamics, Steering Geometry, Steering Drift, Vehicle Pull Nomenclature and moments which govern the control and stability of F Force, N the vehicle. 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. Another thing to note is that no suspension setup is “perfect”. Every car has a center of gravity. As it accelerates, the center of gravity lifts due to suspension squat. Picture two imaginary lines, one represents the steering axis, and the other represents your wheel’s centerline. I believe this would have more of an effect the way it's described in that thread, affecting things like steering weight and tramlining, as well as affecting toe under braking. Positive scrub radius is defined as the steering axis intersecting the ground plane between the vehicle centerline and the contact patch. Cars with a low center of gravity feel like they’re planted to the pavement while those with a higher center of gravity feel less stable. Scrub Radius Description. In this article, we’ll explain what suspension geometry is, how it affects your car, and why it does the things it does. However, having too much toe-out in the front will make your car more unpredictable to handle. Caster is the suspension angle responsible for the self-aligning effect you feel every time you let go of the steering wheel after exiting a corner. The whole idea with rear anti-squat is to dilute this effect by changing where the power is pushing the car. The stock knuckles are a super low scrub radius design, which is nice in some aspects, but they do contribute to the wheel coming in contact with the lower control arm sooner. When opting between the different scrub radius set ups, it’s always best to have a car with a positive or negative scrub radius, even if it’s just slightly in either direction. Each car has different weight distribution, a different chassis, and a different way of delivering power. The effect this has on the movement of your wheels and tires. See all … This happens because of torque steer. Comments. The whole point of having good geometry is to extract the most amount of grip and control out of your tires in all possible conditions. 6° is a good starting point when dialing in caster. The wheel geometry parameters that affect the steerability of the vehicle are camber, caster, Steering Axis Inclination (SAI), scrub radius and toe. The scrub radius will allow the input to have more effect on the steering wheel which could lead to instability. Positive scrub radius helps to maintain steering feel — an important thing to have when you’re driving a race car. In theory at least. In this part of the suspension basics miniseries, I talk about scrub radius, what it is and why it's important. It’s also a standard setting with many double-wishbone suspension designs. To understand why suspension geometry affects your car’s overall behavior, you need to understand suspension angles like camber, caster, toe, scrub radius, and steering axis inclination. So, if you’re making any suspension related modifications to your car, it’s important to be mindful of the changes they’re going to bring about. In these simulations, the disk radius R = 48.27 d was kept constant, and the density was varied by changing the number of dimers confined to the disk. Its purpose is to provide a turning moment that attempts to turn the wheel away from the central position when the vehicle is in motion. The result? In simpler words, when you run any type of scrub radius, your wheels won’t always be pointed dead straight when you brake or accelerate. A flat contact patch at all times! Grip; Tyres; Suspension; Geometry; Geometry Suspension geometry is a mixture of theoretical lines designed into a suspension system to make it work in a particular designed way. It can be defined as: The geometric arrangement of all the components in a suspension system, and the values of all lengths and angles within it. With the MacPherson strut suspension, the steering axis is the straight line between the top strut bearing the lower ball joint. Part 2: https://youtu.be/oh535De4hKgSprings and Anti-roll bar video: https://youtu.be/NFGkZNrNTIE Cars rely on their suspension system to keep their wheels on the ground. When you do this, your caster angle will cause the wheels to align themselves by countersteering for you. When the car body rolls from side to side, it’s going to do so around a pivot point, like a see-saw. ⅛th of an inch is a good place to start. There are over 207,000 people with an additional 78,000 daytime workers within a 5-mile radius of the subject property, with an average household income in excess of $110,000. The result is a scrub radius, which directly affects your car’s stability, handling, and tire wear. Before diving into them, it’ll help to visualize both short-long arm suspension and steering axis inclination.For starters, let’s talk about the steering axis which is a straight line, found between the upper and lower ball joints of the hub on a short-long arm (SLA). Body of The Month By wilke May 3, 2013 Leave a comment. Suspension squat and dive are a result of body pitch. Normally, the SAI angle and the centerline of the tire and the wheel intersect below the road surface, causing a positive scrub radius. Negative scrub radius in the same situation will cause the vehicle to swerve towards the side where there’s less traction. If yes, leave us a comment below! That is, either front or back. It makes the steering response sharper and reduces understeer when entering a corner. The scrub radius is the “lever arm” of longitudinal forces applied at the contact patch (when braking). This is great for reducing tire wear. When you brake and your effort is greater on one side of the car than the other, a positive scrub radius will make the car turn to the side where effort is greater. Scrub Radius: Distance between the point where the steering axis meets the road surface and the tire contact patch. Download File PDF Suspension Camber Toe Caster Analysis 549.214 Aufrufe Part 2: https://youtu.be/oh 535De4hKg Springs and Anti-roll bar video: https://youtu.b e/NFGkZNrNTIE. Your car’s suspension system is never idle, it adapts to whatever you throw at it. The effect of positive or negative scrub radius on the toe angle will depend on whether the vehicle is a front-wheel or rear-wheel-drive design. There needs to be a perfect balance between all parameters of your suspension geometry, including the width of your tires, so that your car can go around the track in the shortest possible time. When you turn your steering wheel, the tire wants to pivot around the point where the KPI meets the road surface. Front camber on a drift car often ranges between negative 4 degrees and 7 degrees depending on the amount of camber gain on lock. The more caster you add, the heavier your steering will feel. At low speed, having a car with zero scrub radius makes it easier to handle. Inclination refers to how diagonal the steering axis is relative to the vertical axis when viewed from the front of the car. If you have an RWD car with a positive scrub radius, the friction between the tire and the road will move the front wheels back and will keep the vehicle going straight. Essentially, the spring is the force pulling the steering wheel toward center; that is to say gravity through caster, KPI and scrub radius (the distance in front view between a car’s king pin axis and the center of the contact patch of the wheel, where both would theoretically touch the road). If it is inboard then the scrub radius is positive. 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. When your car has a significant negative scrub radius, you’ll find that it’s unstable and provides less feedback. You’ll find that a positive scrub radius is useful with certain racing setups. Toe angles can be influenced by the forces acting on your tire, depending on whether you’re accelerating or decelerating. Suspension dive, on the other hand, happens under hard braking — it’s the exact opposite effect. Grip; Tyres; Suspension; Geometry; Geometry Suspension geometry is a mixture of theoretical lines designed into a suspension system to make it work in a particular designed way. In the world of drag racing, there’s only one thing more important than making power — getting that power to the ground. Ie will a 9j et10 wheel have the same scrub radius as a 9j et30 wheel with a 20mm spacer? Post a comment. Getting something like this out of a production car that’s not designed for it requires a few modifications. Because your suspension components are all closely interlinked and work in unison at all times, the smallest change in any angle or measurement will cause a domino effect and impact multiple areas of your entire suspension system — effectively altering your car’s handling. The scrub radius is the distance between the two, where both touch the road. To adjust KPI, and scrub radius as a result, you’d have to move the upper ball joint/strut sideways, either towards or away from the center of your car. KPI measures the angle of your steering axis when viewed from the front, while caster measures how far forward or behind the steering axis sits in comparison to the vertical axis when viewed from the side. Below are the key features that make these things happen…. To see this in action, park your car on a smooth surface, and have someone else operate the steering wheel while you watch your tires turn. The steering is less sensitive to braking with a zero scrub radius. Munkul Active Member. Olet arvostelemassa: Toyota Supra Rear Kit Arvosana. This could have a significant impact on the handling of your car and even affect the advanced driver assistance systems such as lane-keep assist. There are simply too many variables at play. The surface area of this patch that we speak of is your actual scrub radius. Joined: May 2, 2010 Posts: 1,103 Likes Received: 0 Location: Cumbria, UK. On the other hand, using even the slightest amount of toe-out at the rear will make your car twitchy. This line passes through the two ball joints where your wheel mounts to your steering knuckle. Adding a spacer to a wheel WILL change the scrub radius as you change the centre line position. It could get as bad as your car not being able to drive even in a straight line. This is purposeful. Scrub Radius) von XF Motorsports vor 2 Jahren 18 Minuten Page 4/25. Not only does this limit the lock but it sets up the scenario where the gyro will drive the wheel into the control arm at larger angles. Race cars use higher amounts of caster since it makes the front wheels gain camber while turning. To better understand camber, look at your car from the front view and focus on the tires. Labels: Ackerman Counter Steer Drift Included Angle KPI RC Drift RC Drifting Ride Height SAI Scrub Radius Suspension Geometry Thrust Angle. You won’t regret it. If you want to decrease a negative scrub radius, you can fit a smaller diameter tire. When the steering axis intersection point is inside the contact patch, the scrub radius is positive. Steering lock refers to the maximum angular range of your steered wheels. 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. It’s common for FWD vehicles to have a negative scrub radius. If you’ve made it to the end of this article, congrats, because now you know more about suspension geometry and its corrections than many other car enthusiasts out there. However, for mainly road use the effects will be minimal. For example, your car is designed to be driven at stock ride height only. Joined: May 2, 2010 Posts: 1,103 ... Im fairly certain Rotas are one of them, for example a grid drift from et30 to et12. You’ll probably want less toe-in at the rear. What works on a circuit car won’t necessarily work on a drift car. Click to expand... just some with more words and diagrams than necessary, lol #24 Munkul, Jun 26, 2012. jankes … Ideally, you want your drag car to be as light as you can get it, and then find a way to make it hook and go down the track. The manufacturer’s preferred toe specification is determined by the force created by the scrub radius. This is critical for getting the most out of your car’s performance. The angle between the steering axis and the centerline of the wheel is the SAI. Spread the word, and modify responsibly! The ideal thing to do is to run as much positive caster as you can without causing contact between tire and fender. This will move the contact patch away from the hub. Ideally, the scrub radius is as small as possible. To understand why body roll occurs, it helps to know two important concepts: The center of gravity of any car is the central point at which its average mass is summed up. Alternately you can increase the scrub radius by fitting a smaller-size front tire on an RWD car. SAI is easiest to explain by breaking the term up. As a driver, getting ready is just as important as getting the car ready. Caster directly affects the camber angle, causing it to change when you steer. In this guide, we’ll explain what scrub radius is, the different types of scrub radius and their effects on your car’s handling and performance. No if's, but's, weights, dynamic loads, or any other bollocks #144 sparky_s13, Jun 28, 2012. Lisätietoja; Etupää / Takapää : Takapää: Drift / Rata: Drift, Rata: Arvostelut. Required fields are marked *. Write Your Own Review. Running some amount of negative camber on your drift car will allow you to have a wider contact patch at full lock. Toe angle refers to the direction your tires are pointing in when you’re looking at them from the top view. The wheel geometry parameters that affect the steerability of the vehicle are camber, caster, Steering Axis Inclination (SAI), scrub radius and toe. The size of the scrub radius will determine how far it veers. Essentially, the spring is the force pulling the steering wheel toward center; that is to say gravity through caster, KPI and scrub radius (the distance in front view between a car’s king pin axis and the center of the contact patch of the wheel, where both would theoretically touch the road). Knowing what they mean will help you to predict what a particular handling upgrade will do to your car. The scrub radius is the distance at the road surface between the tire center line and the SAI line extended downward through the steering axis. Different suspension systems use positive or negative scrub radius. When you set your car to zero scrub radius, it causes tire scrub in the opposite direction of rotation when you turn. Laatuvaikutelma. Share Get link; Facebook; Twitter; Pinterest; Email; Other Apps; Post a comment August 24, 2015 Sakura D4 Build and Review. Drifting is a driving technique where the driver intentionally oversteers, with loss of traction, while maintaining control and driving the car through the entirety of a corner. These knuckles look really nice, especially for adjust-ability they also appear to have a low scrub radius. For example, cars with a lower steering lock angle will have a wider turning radius and vice versa. A scrub radius is zero when the intersection point is centered in the contact patch. If your dragster can successfully put down all its horses without wheelieing, that’s half the battle won. This is why it’s really important to marry all four of your tires, brake pads, and rotors in a way that they have the same amount of life left. 1. Caster and king pin inclination both essentially measure the same thing but from a different angle. Another benefit is that it provides center point steering when your tire deflates. By increasing caster, you can run less camber when going in a straight line, and get more, much-needed camber in the corners. For example, something as simple as turning your steering wheel will cause your wheels to gain or lose a tiny amount of camber. Essentially, the spring is the force pulling the steering wheel toward center; that is to say gravity through caster, KPI and scrub radius (the distance in front view between a car’s king pin axis and the center of the contact patch of the wheel, where both would theoretically touch the road). The measured steering o set (Scrub Radius) varied drift during braking, which will assist in a better from 6.5 mm at the nominal operating condition design of passenger car front suspension systems for (staticload/de ection) toapproximately 8.5 mmat vehicle stability during braking. The scrub radius simply refers to the distance between the point where the steering axis intersects the pavement and the center of the tire's contact patch. Riset ini telah melalui beberapa tahap dan akhirnya mendapatkan hasil seperti yang diharapkan. Ideally, the scrub radius is as small as possible. You can change your caster angle to dial in the perfect setting. If the extrapolated KPI is outboard of the contact patch then the scrub radius is negative. A car is drifting when the rear slip angle is greater than the front slip angle, to such an extent that often the front wheels are pointing in the opposite direction to the turn (e.g. The best practice is to make sure that the benefits outweigh the penalties for your use case. Sometimes drivers aren’t even aware that they unintentionally change the scrub radius when fitting custom wheels and oversized tires. The most important suspension angles include…. 1 star 2 stars 3 stars 4 stars 5 stars. While we can’t pinpoint the best geometry style for you, we can point you in the right direction. During braking, if the braking effort is more on one side of the vehicle, having a positive scrub radius will cause the vehicle to swerve towards the side where there’s more traction. SAI is an imaginary line, that on strut suspensions runs through the lower ball joints and the upper end of the strut. That is, either front or back. If they did, your scrub radius would increase so much that your car would be difficult to turn. Your other option is to fit a wider wheel, which will move the tire centerline away from the vehicle. Scrub Radius Scrub radius is basically the centerline of the wheel relative to the steering axis inclination (SAI). What are your thoughts and experiences with scrub radius? It also helps to reduce the risk of your car changing direction. Your email address will not be published. Ominaisuudet. Basics. Either if it’s needed to maintain speed with high lock angles in drifting, to get a better start in drag racing or just being faster in circuit racing. Front toe-out is generally more suitable for FWD and AWD cars as it helps to counter their natural tendency to toe in under hard acceleration. To keep the contact patch as flat as possible, negative camber is needed. It … 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. Circuit cars often run a more conservative -2° to -3° of camber, but obviously there are lots of variables here.