Fig.4 - … If the two lines cross exactly at the tyre’s contact patch with the road, there’s no scrub radius, which I think is what TLC were singing about in their 1999 hit single No Scrubs. sheesh. which im running 195/50/15 yokohama AD08rs on. Shop - Suspension & Steering. SCRUB RADIUS. RE: Scrub radius versus grip limit feel ... kinda sorta maybe compensating for the excessive positive scrub radius, variably depending on what the road surface is doing. Too much scrub radius magnifies this stress exponentially. Scrub Plane Radius Offers, Deals and Coupons 2021 - Up To 30% Off Coupon Code - by Getrefe Team Scrub Plane Radius Offers, Deals and Coupons 2021 - Up To 30% Off Coupon Code 5 1 4.1 /5 An increase in wheel and tire diameter can also affect braking in all vehicles. I love to share my knowledge and passion for motorcycles with others. " This can result in a destabilising steering wheel torque at front tyre blow-out. SAI is an imaginary line, that on strut suspensions runs through the lower ball joints and the upper end of the strut. This creates a scrub radius that will affect tire wear and can cause a change in stability. scrub radius value unknown , but 30mm spacers over stock . With a buildup, more offset (less backspace) and greater diameter occur at the same time and the scrub radius often stays in, more or less, the same spot. With a small amount of scrub radius, the tire is turned about the kingpin axis, slightly offset from the tire’s centerline. Steering axis is a line between lower ball joint and the top most pivot of the hub. 88 Audi Quatro, 91 Honda Accord, 94 Nissan Sentra, 98 VW Jetta, 02 VW Jetta, 08 Mazda 6, ( not listed , Bikes , Trucks or Vans ) Radial drive tire specifically recommended for high-traction and high-scrub applications in long- and regional-haul service, light-to-moderate on-/off-highway service, and pickup-and-delivery service. NOTE: Scrub Radius is defined as the point of intersection of the king pin angle ... Yikes, I was WAY off on my specs...the C5 has 1.0 mm of scrub radius. Scrub radius is a distance between Steering Axis Inclination and center of wheel where both of them would theoretically be touching the road. Positive scrub radius would cause both a yaw moment AND a steering reaction in the same direction if you drop a wheel off the pavement. my disk brakes push it out 5/8", so the scrub radius with stock wheel offset is 3 3/4" on my bubbletop (with disk conversion). Back to 4x4 school! Scrub radius helps this feel by providing feedback from the contact patch. so that explains why the tramlining was so awful when i ran 245/45/17 performance tires like that. Common for most heavy vehicles is a positive scrub radius. 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. Post 3419 - Off-road forums & discussion groups. This is probably why AEV moves from 6 inches to 5.2 inches of backspacing with their rims, to account for the increase in diameter from 32 to 35 inch tires with just enough space for the larger size. Save Share. With 0 scrub, as the Mk2 has, when turning the steering without moving causes the wheel to rotate on its own axis/contact patch. (1) parking effort when stationary, brakes off (2) large scrub radius increases kickback through teh steering when under braking due to unequal forces on the front wheels. General Off-Road Forum, Side by side, & ATV groups as well as dirtbike, snowmobile, sandsport and competition racing areas. I transitioned into off-road and raced GNCC, WORCs and National Enduros. 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. ... what i didn't consider was the increased scrub radius - not as it applies to fender clearance ... With normal balljoints I think you’d be a pretty far way off, unless you modified the rack height on the K-member. All lessons and classes are designed by Pro Motocross, Supercross and Off-road … with negative scrub radius is preferred for off-road vehicle .But implementing negative scrub radius results in high degrees of kingpin inclination so small amount of positive scrub radius is preferred and also too much of scrub radius either positive or negative results high steering kickback. Quickly and easily clean away dirt, oils, and grime. More diameter, without changes in backspace, will move the scrub radius in the negative direction (and vice versa). I think that it scrub radius should be looked at as an acceptable range, and that exact OEM measurements are not ultimately necessary. on the bonus side this is a trail buggy so its not that important. Scrub Radius (Kingpin Offset) is the distance between the two points derived from the intersection of the wheel centerline and the steering axis with the ground plane. Two wheels have taken me around the world and I love to share my knowledge and passion for motorcycles with 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. Let's look at the basics of suspension on a real 4x4 instead of a whiteboard. Save Share. A place for off road enthusiasts to chat, share answers, photos, tips, etc. This makes it heavy unless you move a bit too. C5 Z06 - Pit Road. so, the scrub radius turns out to be 3 1/8". I competed for the USA at four International Six Day Events in New Zealand, Chile, Greece and Portugal. I would have thought this might be a … Scrub is important, in my opinion, for two things, on a RWD. Slick Products Scrub Brush is a durable plastic short-handled brush with soft synthetic bristles designed for maneuvering in hard-to-reach areas and safely clean without scratching surfaces. 2. and Leo Laine. Once the lower ball joint is positioned, the upper ball joint is positioned to achieve the desired balance between scrub radius, wheel centre offset and … Scrub radius on front of C5. Importance of Scrub Radius* Kristoffer Tagesson. The science of scrub ... Cars with excessive negative offset wheels can suffer from issues like deflection when hitting rough roads or puddles. Easy-to … Scrub radius will give you bump steer in one-wheel bumps; For high-speed stability in the presence of road disturbances, zero or slight negative scrub radius is desirable (negative is outside the wheel center plane) Braking forces introduce steer torques proportional to the scrub radius. Industry norms are as follows: Sand cars 1/2 to 1” of scrub radius Class 1 off road, 1/2 to 3/4” of scrub radius Trophy Truck 1/4 to1/2” of scrub radius Only three things can change scrub radius. The scrub radius will allow the input to have more effect on the steering wheel which could lead to instability. I've never understood why it took until the 1970s to figure this out and I still don't understand why vehicles are built with a significant positive scrub radius today. 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. Bump steer is bad. The scenario where scrub radius becomes an issue with off road cars is in situations where the wheels are encountering large undulations such as rocks or mud banks and the force on the tyre is trying to turn the wheels. But, with a positive scrub radius, you then have a small radius, from the KPI axis contact point with the ground, out to the centre of the contact patch. If there is a change in ride height front to rear on a passenger car, it can affect caster and steering. For off-road performance, we prefer to stick to the rule of thumb of running a wheel diameter no bigger than half the tire height. Off-Road Racing Community. see the problem with that for me is that the scrub radius and all that is dictated more by tire fitment than what is right, I have a frontend out of a cherokee under a cj-31 and am going to end up in a 15x10 wheel with 2-3 inches of backspacing and 16-38-15 swampers, tell me my scrub radius is not gonna be right whacked! This creates a small tire/road friction resistance that in turn translates into feedback from the road. Hence a small scrub radius will make the car less sensitive to changes in steering when braking. "Two wheels have taken me around the world. Bump steer is a super common and misunderstood problem. Nomenclature F Force, N K Stiffness, ... motion of vehicles on a road surface. Former oldies. however ive done alot of research lately into the effects of running low offset wheels for a … 1, Bengt Jacobson. Mk1 Mx5 Wheel Offset/scrub Radius Help Needed! As I am in a position to slightly change the scrub radius with the wheel off set, what should I be looking at. Younggun Cho … 1. Negative scrub radius seem to have stabilising effect on vehicle handling. Shop. Tire diameter certainly affects scrub radius as it changes the point where the two axis intersect. Reply. In this study the On the McPherson strut, top most pivot point is a strut bearing whereas the bottom point consists of lower ball joint. Scrub radius changes not only from backspace but from changes in diameter too. Non-scratch soft bristles. My reference is SAE SP-1282, page 27. RWD only is 0"-3". - posted in Wheels, Tyres, Suspension & handling/etc: Hi guys Basically i bought some 7twenty style 44s, 15x8 et0, about a year ago. The dynamic behaviour of a vehicle is determined by various kinds of ... design changes require trade-offs to maintain perfect balance. 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 … To minimise scrub radius, the lower control arm ball joint is typically positioned as far outboard as possible whilst still allowing for brake disk package. ... say, if the left-hand wheels have less grip and the ABS backs the system off on that side. scrub radius. Abstract—Front tyre blow-outs lead to several fatal accidents involving heavy vehicles. Steeda tech support. i have since done a track day and thought they performed okay. Also covers jeep, land use, Toyota – Ford – GM. Drop a wheel off and the vehicle takes off into the ditch. Road Racing/Auto X. sn95 spindles - ackermann & scrub radius. As the tire height and weight goes up, the scrub must go down. Feedback from the road resistance that in turn translates into feedback from the road easy-to … scrub radius magnifies stress. 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