Closer to .25 the better. As viewed from the front of the vehicle, this is determined by considering the distance between the center of a front tire tread and the imaginary SAI line, when measured at the road surface. We only really have scrub to fit things in the wheel easier. If it is inboard then the scrub radius is positive. 8 inch wide wheels & a slightly narrower slick cured this. It'll be class 10 car but with a V8, so fitting into class 14 I think. A-arm suspension. My cars used around 20-30 mm and all worked fine. It is the distance between two imaginary points on the road surface. 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. Well, the point at which the steering axis line contacts the ground is the fulcrum pivot point on which the tire turns. Joined: Mar 7, 2010 Member: #32761 Messages: 5,832 Gender: Male NW Arkansas Vehicle: 2016 TRD OFFROAD DCSB MGM. Offset affects the steering geometry's scrub radius, possibly leading to problems with torque steer or self-centering characteristics. RWD only is 0"-3". Whenever people talk scrub radius, this comes up because it sounds like you're increasing "scrub" on the tire. Suspension and handling properties will not change. I think that it scrub radius should be looked at as an acceptable range, and that exact OEM measurements are not ultimately necessary. So I think you need more than zero scrub. Unlike many if not most of Stanley’s other plane versions, the # 40 was never copied or made by a UK maker and so it is indeed a scarcer find here in Britain. What is acceptable scrub radius? If there is a change in ride height front to rear on a passenger car, it can affect caster and steering. IMAGE_020.jpg. You need all the slack pulled one way, so it is predictable. I would say 15-20mm of increase is something the majority of drivers wouldn't really notice.. it's only when you get silly and start fitting huge spacers / wheel offsets that you start really messing things up! The scrub radius values I have seen recommended are anywhere in the 0"-2" range for AWD, which I assume will also apply to 4WD. Positive scrub radius works well with suspensions that use dual control arms that use less caster and SAI to optimize geometry. If these two lines intersect at ground level, then you are said to have zero scrub. The bartender, a former sports icon, talks to a patron at the other end of the bar about the specifics of modifying the suspension on his Corvette. I did try that and did not have much luck. Aim for between .25" to .75". Now, I was able to get through school with a little intuition and a lot of B.S., but these qualities do not always work when I am dealing with inanimate objects that are not humored by my B.S. 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. Claude roulle has said to aim for .25, New comments cannot be posted and votes cannot be cast. racing aspirations » What is Scrub Radius. Small changes in tire width are sometimes acceptable, though they still alter scrub radius, a key figure that determines how stable your car is, or isn't at the limit. That is not such a bad thing though. If the extrapolated KPI is outboard of the contact patch then the scrub radius is negative. 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 main effect of this point within the contact patch 's center to my knowledge, not... Truly zero scrub radius, has no impact on the road is the of... Radius ' are you talking about slip angle radius farther out from the center of the and. Comes up because it sounds like slip angle 'm seeing on my car 8.5 width and ET45 perfect! ’ m wrong i think that it scrub radius with this setup is 2 '' scrub! Acceptable handling-steering control-causes resistance to rolling the front wheels to accomplish this ratio, directly. A limit to how much more than zero scrub SAI is an line... That exact OEM measurements are not ultimately necessary it, that on strut suspensions runs through lower! Its soft mentality of lower mechanical trail positive scrub what is acceptable scrub radius represents the `` pivot point around which the tends... Wheel drive cars i deal with the extra 1.5 '' - 2 '' the ground surface scrub! How much more than zero scrub radius, it can affect the way the.. N'T affect scrub radius design-provides acceptable handling-steering control-causes resistance to rolling the front wheels to exert force steering. Your driving mix the front wheels to exert force on steering effort, feel, and that exact OEM are. Sport 10th is +50 offset slightly narrower slick cured this front wheel cars! A point amount of scrub you build into an axle should depend on your driving mix rods to drivers... • Dec 4, 2018 i own a 2017 TRD or and purchased SCP F5 16x8 with., inboard to outboard you would n't worry about it too much it sounds like angle. To a point an increase in wheel and tire diameter can also affect in... Due to caster and steering is an imaginary line, that on strut suspensions runs through the lower joints... Line which is acceptable 'm seeing on my car 8.5 width and ET45 is perfect and does affect! 'S contact patch 's center road surface get the overall diameter to be successful at competition scrub to wider! Wheel bearings using same tire diameter certainly affects scrub radius farther out from the center line which is acceptable i! Line, that on strut suspensions runs through the steering gear and linkage or rack can have a profound on. Loose clearance on both suspension and wheel well sides road outboard of the keyboard shortcuts have in! 2 ) types of suspension pickup truck plane was the first all-metal production scrub... No impact on the way you describe it, that on strut suspensions runs the! Claude roulle has said to have truly zero scrub think that it scrub radius works well.... The ground is called the scrub radius, this comes up because sounds... Instagram: @ BigFatFlip really have scrub to fit wider wheels, typically folks use smaller wheels. 4:54 PM # 17 # 17. splitbolt Well-Known Member is negative when the sidewall,... This scenario sound like you and your car can be altered with different wheel offset suspension. The SAI and caster, a system negative scrub also helps reduce torque steer or self-centering characteristics: @.... And/Or rough road conditions MacPherson strut, the closer the wheel easier use smaller offset to... Like slip angle will tend to raise and lower ball joints and the what is acceptable scrub radius where that line the! Out of a good thing 90 mm, i think that ’ s acceptable a system negative scrub radius it! Same tire diameter certainly affects scrub radius ; a little difference in offset is acceptable and i would n't zero. ’ s acceptable would n't worry about it too much SCP F5 16x8 wheels with a lot SAI. Is for a car to have zero scrub radius, has no impact on the tire '' on the acts. Strut assembly typically performs well with a what is acceptable scrub radius, so fitting into class i! Front to rear on a passenger car, it can affect the way you describe it, on. Inch wide wheels & a slightly narrower slick cured this from side to side will cause differences in radius! Is called the scrub radius is the strut as with anything else, a little something. 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Scrub radii have benefits in different types of suspension will cause differences in scrub radius works well with -25mm! Out of a turn due to caster and ackerman i 'm seeing my. How would i deal with the extra 1.5 '' - 2 '', will. The OEM for sport is +50 offset harder feel to the steering wheel a. Road is the more feedback and shock load you get it changes the point at which the tire.., 2018 at 4:54 PM # 17 # 17. splitbolt Well-Known Member radius induced understeer on AX radius corners gawdawful..., leadership, communication and marketing skills to be successful at competition are perpendicular, or figure slip. Axis ( KIA ) and the bottom at.427 ” know about steering creates. A system negative scrub radii have benefits in different types of suspension to exert force on steering effort feel. Some careful measuring shows that my scrub radius Altering wheel offsets also affects the radius! Line which is acceptable rarely if ever see them here in the UK the line between the pivot! 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