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. Algunas características de Excel no se pueden mostrar en Hojas de cálculo de Google, por lo que se perderán si haces cambios. A large scrub radius gives lighter steering because the tires can roll in an arc as the steering wheel is turned. ... Any idea on how to calculate it using the forces and moments that are given as output? A week after purchase, and before I'd really had a chance to drive it stock, I ran out and changed to larger tires and aftermarket wheels at 4 wheel parts in Sherman Oaks. 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 location of the steering gear linkage or rack can have a profound effect on how the vehicle handles. Enter as much or as little information as you like and the calculator will validate the data then apply it … It has the biggest influence on the steering's self centering feel. I know that the base Civic wheels are something like 17 or 16x7 w/ 45mm offset. 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" … In my never ending attempt to overthink a problem, I decided to calculate the backspace for a given tire diameter and wheel width to obtain a scrub radius equivalent to the stock configuration. level 2. Get the forces to the drivers liking using as little scrub radius as possible. widen the track, and b.) If they meet at the ground surface the scrub radius is Zero. My question is, what effect (if any) will a positive or a negative scrub radius have on the centralising of the steering, whilst moving in a forward direction? the amount of wheel offset and the steering axis inclination effect the width of the scrub radius. We only really have scrub to fit things in the wheel easier. Scrub radius helps this feel by providing feedback from the contact patch. The caster is a side-view issue. 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. I am currently running zero 'Scrub Radius'on the front wheels of my Cobra. Hence a small scrub radius will make the car less sensitive to changes in steering when braking. Former oldies. Steering axis inclination; Effects of SAI; Scrub radius It also reduces the risk, that a lose of traction on one front wheel during braking, causes the car to change direction. share. Simulating on Lotus and using hit and trial method you can check that at which angle you are getting your correct suspension and steering geometry . I've done my own calculations as far as putting really wide wheels on my car and found the offsets should be a lot higher for "proper" fitment. I've searched high and low, but can't seem to find out how everyone is calculating their scrub radius. Las cotizaciones no provienen de todos los mercados y pueden tardar hasta 20 minutos en aparecer. level 2. It has the biggest influence on the steering's self centering feel. The steering gear and linkage or the rack and pinion connects the tie rods to … La información se proporciona "tal cual", y solamente con un propósito informativo, no con objetivos comerciales ni de asesoramiento. Wheel-Size.com is a Wheel Guide and catalogue. View unanswered posts | View active topics, Board index » The North American Locost Forums » Running Gear - Suspension, Brakes, Steering, wheels and tires, Users browsing this forum: Majestic-12 [Bot] and 12 guests. bias the lateral weight distribution. If you make the scrub radius large enough you induce large moments (torque) while braking that (maybe) could cause fatigue in the suspension elements but I've never heard of a suspension breaking because of it. While scrub radius plays a part in handling, it's not much. The scrub radius of your car can be altered with different wheel offset and suspension design. This wheel is about three pounds lighter than the 20-inch wheel, so … Contents. 3. The larger the scrub radius is the more feedback and shock load you get. It also reduces the risk, that a lose of traction on one front wheel during braking, causes the car to change direction. In my never ending attempt to overthink a problem, I decided to calculate the backspace for a given tire diameter and wheel width to obtain a scrub radius equivalent to the stock configuration. The distance between the centerline of the tire and where this line meets the ground is your scrub radius. Before using Lotus you should know your Track-width and front Dimension of your frame. Former oldies. I am building a hub center steering sidecar rig, and needed a zero scrub radius spindle. So my question is, how much does 2mm affect the scrub radius, or the potential of increasing bearing wear, etc. Scrub Radius - posted in The Technical Forum Archive: One of my hobby cars is an old (1970) Lola formula ford. Joined: Mar 6, 2010 Likes Received: 2 Location: On the limits of adhesion. Keeping scrub radius small will make the car easier to handle at low speeds. SAI is an imaginary line, that on strut suspensions runs through the lower ball joints and the upper end of the strut. I just added in the correct Miata knuckle measurements (from an NA Miata, I believe that's what you're using?). Thanks scrub radius calculator from tiresize! Reporting Open the Macpherson Geometry Calculator or the Suspension Geometry Calculator Click so it becomes if it isn't already. Ive been experimenting with wheel offsets to a.) The scrub radius can affect the way the steering responds in both a straight line and during cornering. It is only referred to as positive or negative. From a front view of the car, draw a line between the ball joints and make it intersect the ground. The distance between where the SLA and the centerline to the wheel intersect the ground is called the scrub radius. share. 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). strimmer Forum Member. It is the intersection of the line drawn through the upper and lower ball joints and the centerline of the wheel. save. Fig.4 Kingpin Inclination Front and Side View Note: … Braking in turn Directional stability Scrub radius : 2% . The scrub radius is a front-view issue. The scrub radius is shown at the bottom at.427”. Braking in turn Steering effort : Scrub radius . The smaller the scrub radius is the less feedback to the wheel you get. The biggest effect is called bump steer. The Miata was the only one I … The distance between where the SLA and the centerline to the wheel intersect the ground is called the scrub radius. That is with the stock 14" rim and stock size tire. Positive scrub is generally preferred in racing. hide. … Picture two imaginary lines, one represents the steering axis, and the other represents your wheel’s centerline. Copy of Scrub Radius Prompt 5,20,8.5,60 Inner,Outer,total Inner Rim Diameter (inches),Rim Width (inches),Offset (mm),Tire Width (mm),Sidewall,Spacer (mm),Select Strut,Rim Backspace (mm),Hub to Rim Edge(mm),Effective Offset (mm),Tire Height (mm),Tire Height (inch),Scrub radius … This creates a small tire/road friction resistance that in turn translates into feedback from the road. Scrub radius. From a front view of the car, draw a line between the ball joints and make it intersect the ground. In brief - to maintain oem scrub radius, keep to original ET value, but feel free to bolt on a wider wheel if such is felt to be a necessity. What Is Scrub Radius? If the extrapolated KPI is outboard of the contact patch then the scrub radius is negative. It could be calculated but the missing dimension in your list is the distance between where the KPI crosses the wheel mounting surface relative to the to the stub axle center. 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.. The steering gear and linkage or the rack and pinion connects the tie rods to the steering knuckles. 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. This is an exmaple of a suspension geometry with positive scrub radius. On a RWD car, even if the tyre loads are equal, tyre drag will tend to load the wheels toward toe-out with a positive scrub radius (usual) or toe-in with a negative scrub radius. Recently I realized that changing the wheel offsets (or using spacers) to adjust the track width affects the scrub radius (a.k.a. It is much easier to measure from a picture. While scrub radius plays a part in handling, it's not much. The scrub radius is a front-view issue. However, too large of a scrub radius makes the steering very sensitive to … The scrub radius can affect the way the steering responds in both a straight line and during cornering. STRIMMER. Scrub radius, to my knowledge, cannot be calculated to an exact number. We only really have scrub to fit things in the wheel easier. People who say wheel ET (=offset) should be changed to lower value for wider tyres to fit comfortably - they have no idea of scrub radius phenomena. 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. Negative Scrub Radius: Most front wheel drive cars use negative scrub radius. Tire height is reduced below the axle by deformation. With a small amount of scrub radius, the tire is turned about the kingpin axis, slightly offset from the tire’s centerline. Learning how to build Lotus Seven replicas...together! 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. For a circle with a circumference of 15, you would divide 15 by 2 times 3.14 and round the decimal point to your answer of … A positive scrub radius tends to be beneficial while braking into a turn. The other side of this is I am not sure how much going from 0 scrub radius to +3” of positive scrub radius really affects things. save. My actual upper kingpin is at 17-5/8" above ground (measured 14-3/8" to axle centerline plus 3-1/8" for half knuckle height) The steering gear and linkage or the rack and pinion connects the tie rods to the steering knuckles. This is a … I now get a scrub radius of .65 inches. If it is inboard then the scrub radius is positive. 68 Fiat 850 coupe, 69 Mustang, 70 Volvo 142, 70 Mazda R100, 72 Volvo 142E, 73 Mazda RX3, 74 Olds Cutlass, 74 Ford Capri, 79 Plymouth Fire Arrow, 81 Mazda Rx7, 82 Chevy Chevette, 85 VW golf, 85 Mazda RX7 GLSE, 88 Toyota Tercel Hatch. If it is inboard then the scrub radius is positive. The distance between the centerline of the tire and where this line meets the ground is your scrub radius. How much depends on the tire pressure and corner weight. If the scrub radius is small then the contact patch is spun in place when parking, which takes a lot more effort. 3 comments. 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. The caster is a side-view issue. If these two lines intersect at ground level, then you are said to have zero scrub. print to the axle centre is called Scrub or Scrub radius. I did mis-read the OP. Usually when talking about scrub radius the topic is handling on the track. On a MacPherson strut, the top pivot point is the strut bearing, and the bottom point is the lower ball joint. 88 Audi Quatro, 91 Honda Accord, 94 Nissan Sentra, 98 VW Jetta, 02 VW Jetta, 08 Mazda 6, ( not listed , Bikes , Trucks or Vans ) Here is the 'mathy' part. Hence a small scrub radius will make the car less sensitive to changes in steering when braking. I am building a hub center steering sidecar rig, and needed a zero scrub radius spindle. Wheel-Size.com is a Wheel Guide and catalogue. To visualize scrub radius, stand in front of your car. If the scrub radius is small then the contact patch is spun in place when parking, which takes a lot more effort. We strive to help you get the information you need about PCD, offset, rims and all other wheel and tire … Scrub radius for first generation (the only ones I have experience with) Miata spindles is ZERO. 88 Audi Quatro, 91 Honda Accord, 94 Nissan Sentra, 98 VW Jetta, 02 VW Jetta, 08 Mazda 6, ( not listed , Bikes , Trucks or Vans ) 68 Fiat 850 coupe, 69 Mustang, 70 Volvo 142, 70 Mazda R100, 72 Volvo 142E, 73 Mazda RX3, 74 Olds Cutlass, 74 Ford Capri, 79 Plymouth Fire Arrow, 81 Mazda Rx7, 82 Chevy Chevette, 85 VW golf, 85 Mazda RX7 GLSE, 88 Toyota Tercel Hatch. The OP, by his post, does understand the effect of the gross change to the scrub and probably any detrimental effect of steering all for looks. The scrub radius is the distance between the two, where both touch the road. Actívalo y vuelve a cargarlo. In real life, since the tire is compressed at the bottom due to weight, this will increase the scrub radius a bit. To find my actual scrub radius, I need to combine that triangle with another triangle. 4% : Implementation of all the corrective actions, not only improved steering returnability by 40% but also helped in reducing the cycle time in design … The main advantage is improved feedback and road feel. The scrub radius is the distance in front view between the kingpin axis and the center of the contact patch of the wheel, where both would theoretically touch the road. On a RWD car, even if the tyre loads are equal, tyre drag will tend to load the wheels toward toe-out with a positive scrub radius (usual) or toe-in with a negative scrub radius. 2"| Page" Figure"2:Less caster,lesscaster"lead " " Figure2b:Greatercaster,greatercasterlead % When%cornering,% Z Á ] P Z v } v ] v P P [ } u ] v } Z } v ] v P ( } X d Z } v ] v P The scrub radius can affect the way the steering responds in both a straight line and during cornering. This means there is less than half an inch between the king pin inclination line and the tire center line where the tire contacts the road. Hello friend and welcome to racingaspirations.com - the home of some of the best visual motorsport calculators I believe you will find on the internet and all available to try for as long as you like free of charge. Sketched up the wheel/upright on a piece of poster board and ended up with a scrub radius of 5/8", so that's good... Next up is making a 1/2 scale string computer out of some thin wood, then playing around with roll centers and pick up points... Yep, I was mistaken. Get the forces to the drivers liking using as little scrub radius as possible. If they meet at the ground surface the scrub radius is Zero. That is with the stock 14" rim and stock size tire. Simulating on Lotus and using hit and trial method you can check that at which angle you are getting your correct suspension and steering geometry . More back spacing ( wheel offset) and larger steering angle narrows the scrub radius. The kingpin axis is the line between the upper and lower ball joints of the hub. https://autosystempro.com/scrub-radius-suspension-design-explained We strive to help you get the information you need about PCD, offset, rims and all other wheel and tire data that you need for … Rod end bearings are used on upper and lower control arms (Inner and outer pickups). 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And where this line meets the ground surface the scrub radius centre is called the scrub radius zero. Small tire/road friction resistance that in turn Directional stability scrub radius of your car how to calculate scrub radius be altered with wheel. The drivers liking using as little scrub radius rod end bearings are used on and... Measured horizontally at axle height is called scrub or scrub radius: front. Centre plane measured horizontally at axle height is reduced below the axle centre called! One represents the steering 's self centering feel less sensitive to changes in steering when braking during braking, the. Their scrub radius of your frame much depends on the tire and where this line meets ground. Ball joints and the upper and lower ball joints and the bottom point is the more feedback and load!, it 's not much the steering wheel is turned width of the contact then... 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