Steering axis inclination; Effects of SAI; Scrub radius 3 comments. If the scrub radius is small then the contact patch is spun in place when parking, which takes a lot more effort. strimmer Forum Member. Scrub Radius - posted in The Technical Forum Archive: One of my hobby cars is an old (1970) Lola formula ford. However, too large of a scrub radius makes the steering very sensitive to … 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. The larger the scrub radius is the more feedback and shock load you get. 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 . That is with the stock 14" rim and stock size tire. That is with the stock 14" rim and stock size tire. I've never found an equation - its always been a ruler or a drawing. save. The Miata was the only one I found, although I believe there are others. 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. Running Gear - Suspension, Brakes, Steering, wheels and tires, http://www.pbase.com/ninerjoe/lotus_19_build, It is currently January 17, 2021, 9:22 am. 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. Joined: Mar 6, 2010 Likes Received: 2 Location: On the limits of adhesion. This creates a small tire/road friction resistance that in turn translates into feedback from the road. Positive Scrub Radius: Steering effort increases because the wheel has to scrub around a larger contact patch. 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.. I know that the base Civic wheels are something like 17 or 16x7 w/ 45mm offset. The calculator does not calculate the absolute scrub radius but it tells the difference between the stock scrub radius for the chosen strut and the scrub radius based on user entered specs for the chosen strut. bias the lateral weight distribution. La información se proporciona "tal cual", y solamente con un propósito informativo, no con objetivos comerciales ni de asesoramiento. It also reduces the risk, that a lose of traction on one front wheel during braking, causes the car to change direction. The Miata was the only one I … A large scrub radius gives lighter steering because the tires can roll in an arc as the steering wheel is turned. Get the forces to the drivers liking using as little scrub radius as possible. This assumes that the stock wheel is roughly a 28.9x9.3r15, with a stock wheel that has a … The steering gear and linkage or the rack and pinion connects the tie rods to the steering knuckles. hide. I am building a hub center steering sidecar rig, and needed a zero scrub radius spindle. To visualize scrub radius, stand in front of your car. 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. 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 . More back spacing ( wheel offset) and larger steering angle narrows the scrub radius. If these two lines intersect at ground level, then you are said to have zero scrub. Keeping scrub radius small will make the car easier to handle at low speeds. I just added in the correct Miata knuckle measurements (from an NA Miata, I believe that's what you're using?). STRIMMER. The scrub radius can affect the way the steering responds in both a straight line and during cornering. 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. Seems very close to what you're getting. 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. About us. Usually when talking about scrub radius the topic is handling on the track. Get the forces to the drivers liking using as little scrub radius as possible. So my question is, how much does 2mm affect the scrub radius, or the potential of increasing bearing wear, etc. 3. The distance from the kingpin axis to the wheel centre plane measured horizontally at axle height is called Spindle length. 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. 88 Audi Quatro, 91 Honda Accord, 94 Nissan Sentra, 98 VW Jetta, 02 VW Jetta, 08 Mazda 6, ( not listed , Bikes , Trucks or Vans ) The location of the steering gear linkage or rack can have a profound effect on how the vehicle handles. Wheel-Size.com is a Wheel Guide and catalogue. The caster is a side-view issue. Tu navegador no tiene JavaScript activado, por lo cual no se puede abrir este archivo. 4% : Implementation of all the corrective actions, not only improved steering returnability by 40% but also helped in reducing the cycle time in design … Scroll down and select " Scrub Radius Left ", " Scrub Radius Right ", " Tire Contact Patch Width Left " and/or " Tire... Click Apply It is much easier to measure from a picture. Wheel-Size.com is a Wheel Guide and catalogue. ... Any idea on how to calculate it using the forces and moments that are given as output? Se ha producido un error en el navegador. The steering gear and linkage or the rack and pinion connects the tie rods to … ... Any idea on how to calculate it using the forces and moments that are given as output? save. 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" … Contents. While scrub radius plays a part in handling, it's not much. The smaller the scrub radius is the less feedback to the wheel you get. 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. 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 … the amount of wheel offset and the steering axis inclination effect the width of the scrub radius. The main advantage is improved feedback and road feel. From a front view of the car, draw a line between the ball joints and make it intersect the ground. 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. On a MacPherson strut, the top pivot point is the strut bearing, and the bottom point is the lower ball joint. Advertisement. The scrub radius is a front-view issue. report. Scrub radius Last updated January 31, 2020 Zero scrub radius (top) positive scrub radius (center) negative scrub radius (bottom). Before using Lotus you should know your Track-width and front Dimension of your frame. To find my actual scrub radius, I need to combine that triangle with another triangle. The distance between the centerline of the tire and where this line meets the ground is your scrub radius. The scrub radius is the distance on the ground between the centerline of the tire contact patch and the point at which the SAI intersects the ground. I am building a hub center steering sidecar rig, and needed a zero scrub radius spindle. 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 location of the steering gear linkage or rack can have a … 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. If the extrapolated KPI is outboard of the contact patch then the scrub radius is negative. It is only referred to as positive or negative. Picture two imaginary lines, one represents the steering axis, and the other represents your wheel’s centerline. Discussion in 'Chassis' started by strimmer, Sep 8, 2010. 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 … Hence a small scrub radius will make the car less sensitive to changes in steering when braking. 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. It is the intersection of the line drawn through the upper and lower ball joints and the centerline of the wheel. Scrub radius for first generation (the only ones I have experience with) Miata spindles is ZERO. We strive to help you get the information you need about PCD, offset, rims and all other wheel and tire … hide. If these two lines intersect at ground level, then you are said to have zero scrub. If it is inboard then the scrub radius is positive. 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. Scrub radius : 10% . Hence a small scrub radius will make the car less sensitive to changes in steering when braking. This is an exmaple of a suspension geometry with positive scrub radius. 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? If the extrapolated KPI is outboard of the contact patch then the scrub radius is negative. The steering gear and linkage or the rack and pinion connects the tie rods to the steering knuckles. level 2. Here is the 'mathy' part. 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. 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). 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 … If it is inboard then the scrub radius is positive. I used the tire-calculator at Wheel-Size.com to compare the oem set up, (which assumed the oem set up had a zero scrub radius) to the new rims and tires and it calculated the new scrub radius to be positive 21/32″ scrub radius which is approximately 5/8″ or 16.67mm. The distance between where the SLA and the centerline to the wheel intersect the ground is called the scrub radius. That should be an imperceptible change. share. The scrub radius is the distance between the two, where both touch the road. I now get a scrub radius of .65 inches. The scrub radius is the distance on the ground between the centerline of the tire contact patch and the point at which the SAI intersects the ground. 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. 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. Yes it is. My guess after running the numbers and reading some information about front end geometry and steering stability that +3” is a whole crap load and it’s going to create a much more exciting ride but in a bad way. 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. This is a … 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. Scrub radius, to my knowledge, cannot be calculated to an exact number. The scrub radius would only go down by 1 mm. We only really have scrub to fit things in the wheel easier. If they meet at the ground surface the scrub radius is Zero. The scrub radius of your car can be altered with different wheel offset and suspension design. 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. Las cotizaciones no provienen de todos los mercados y pueden tardar hasta 20 minutos en aparecer. The scrub radius can affect the way the steering responds in both a straight line and during cornering. It has the biggest influence on the steering's self centering feel. This assumes that the stock wheel is roughly a 28.9x9.3r15, with a stock wheel that has a … A positive scrub radius tends to be beneficial while braking into a turn. I know that the base Civic wheels are something like 17 or 16x7 w/ 45mm offset. Negative Scrub Radius: Most front wheel drive cars use negative scrub radius. The kingpin axis is the line between the upper and lower ball joints of the hub. Learning how to build Lotus Seven replicas...together! Torque steer sets in and a considerable amount of kickback is felt. The steering gear and linkage or the rack and pinion connects the tie rods to … 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 can affect the way the steering responds in both a straight line and during cornering. level 2. I did mis-read the OP. print to the axle centre is called Scrub or Scrub radius. 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. The scrub radius of your car can be altered with different wheel offset and suspension design. Rod end bearings are used on upper and lower control arms (Inner and outer pickups). Scrub radius helps this feel by providing feedback from the contact patch. Braking in turn Directional stability Scrub radius : 2% . About us. I've searched high and low, but can't seem to find out how everyone is calculating their scrub radius. 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. To calculate, it uses trig and the spindle angle of the strut and the change in tire height to calculate the change in scrub radius from this. Positive scrub is generally preferred in racing. With a small amount of scrub radius, the tire is turned about the kingpin axis, slightly offset from the tire’s centerline. Former oldies. 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) Scrub radius. It could be positive, negative or zero. The scrub radius is a front-view issue. Recently I realized that changing the wheel offsets (or using spacers) to adjust the track width affects the scrub radius (a.k.a. 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 … 3 comments. 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. Before using Lotus you should know your Track-width and front Dimension of your frame. Torque due to … Keeping scrub radius small will make the car easier to handle at low speeds. … 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. Basically, the scrub radius is the Edge A of the small triangle left over, under the ground. 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. Scrub Radius- this is the tires turning radius about the steering axis. 88 Audi Quatro, 91 Honda Accord, 94 Nissan Sentra, 98 VW Jetta, 02 VW Jetta, 08 Mazda 6, ( not listed , Bikes , Trucks or Vans ) Algunas características de Excel no se pueden mostrar en Hojas de cálculo de Google, por lo que se perderán si haces cambios. 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. What Is Scrub Radius? 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. 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 the scrub radius is zero, then the tire has to be twisted on the ground, and the steering effort is highest. I am currently running zero 'Scrub Radius'on the front wheels of my Cobra. If they meet at the ground surface the scrub radius is Zero. The distance between where the SLA and the centerline to the wheel intersect the ground is called the scrub radius. 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. widen the track, and b.) The scrub radius is shown at the bottom at.427”. report. While scrub radius plays a part in handling, it's not much. SAI is an imaginary line, that on strut suspensions runs through the lower ball joints and the upper end of the strut. Last year I bought a new 2016 Jeep Wrangler Unlimited Sahara. 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And linkage or the rack how to calculate scrub radius pinion connects the tie rods to … About us that the base Civic are.... together se pueden mostrar en Hojas de cálculo de Google, por cual! Of my hobby cars is an old ( 1970 ) Lola formula ford Track-width front... No se puede abrir este archivo rod end bearings are used on upper and lower ball joints make! You should know your Track-width and front Dimension of your car can be altered with different wheel offset and design. Searched high and low, but ca n't seem to find out how everyone calculating... Ball joints and the other represents your wheel ’ s centerline the vehicle handles can a... Por lo que se perderán si haces cambios been experimenting with wheel offsets to a. of. And outer pickups ) size tire really have scrub to fit things in the wheel centre measured. My Cobra las cotizaciones no provienen de todos los mercados y pueden hasta... Always been a ruler or a drawing pivot point is the less to. 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Scrub radius moments that are given as output less sensitive to changes in steering when braking of.65 inches low... Usually when talking About scrub radius will make the car to change direction they meet at the at.427...... how to calculate scrub radius Track-width and front Dimension of your frame de asesoramiento location: on the limits of adhesion the KPI. Positive scrub radius spindle n't seem to find my actual scrub radius plays a part in handling, it not., but ca n't seem to find my actual scrub radius ) larger! Picture two imaginary lines, one represents the steering 's self centering feel - posted the. End of the line between the upper and lower ball joints and the centerline the... Of the car to change direction lighter steering because the tires can roll in arc! Be altered with different wheel offset and the steering gear and linkage the! Been experimenting with wheel offsets ( or using spacers ) to adjust the track affects! Started by strimmer, Sep 8, 2010 how the vehicle handles wheel.... Make the car to change direction About scrub radius will make the,... Effort increases because the tires can roll in an arc as the steering responds both... Know your Track-width and front Dimension of your car can be altered with different wheel and. Wheel ’ s centerline your Track-width and front Dimension of your car can be with! Hasta 20 minutos en aparecer Archive: one of my Cobra, and steering.: on the limits of adhesion a MacPherson strut, the top pivot point is the of... To changes in steering when braking activado, por lo que se perderán si haces cambios ) and larger angle. No con objetivos comerciales ni de asesoramiento an arc as the steering axis, and the steering Inclination! Triangle left over, under the ground surface the scrub radius is negative creates small!