What is positive scrub radius?

The distance between the center of the tire's contact patch and the point where that line touches the road is the scrub radius. If the line touches the road inboard of the contact patch, scrub radius is positive. If the line touches the road outboard of the contact patch, scrub radius is negative (see Figure 2).

Is positive or negative scrub radius better?

Negative scrub radius decreases torque steer and improves stability in the event of brake failure. SLA suspensions usually have a positive scrub radius. With this suspension, the scrub radius is not adjustable. The greater the scrub radius (positive or negative), the less the steering effort is.

Why is the radius of a scrub positive?

Positive Scrub Radius will increase steering effort, torque steer (Making the car harder to control during turning and cornering) and kickback on bumps to a considerable degree. At the same time,a blowout or a failure of one front brake could yank the wheel hard enough to pull it out of your hands.

What is scrub radius and why is it important?

Negative scrub radius allows the road forces to toe-out the front tires and reduce torque steer tendencies when accelerating. The manufacturer's specification will be positive (toe-in) to produce a near-zero dynamic toe.

What is positive scrub?

With a positive scrub radius, the tire will not turn on its centerline, causing it to scrub the road when you turn. For you, this means exerting more effort. When your vehicle is too positive, it will cause the brakes to dart when you apply them.

How Scrub Radius Works

How is scrub radius measured?

From a front view of the car, draw a line between the ball joints and make it intersect the ground. The distance between the centerline of the tire and where this line meets the ground is your scrub radius.

What is a positive offset on a wheel?

Positive wheel offset is when the hub mounting surface is in front (more toward the street side) of the centerline of the wheel. Most wheels on front-wheel drive cars and newer rear-drive vehicles have positive offset. Negative offset is when the hub mounting surface is behind the wheel centerline.

What is positive caster?

Caster angle settings allow manufacturers to balance steering effort, high speed stability, and front end cornering effectiveness. Positive Caster - If the line slopes towards the rear of the vehicle, then you have positive caster. The down side to positive caster is if the vehicle does not have power steering.

Does changing wheel offset affect alignment?

However, slight changes in the offset (like -10 to zero) aren't changing the geometry and you don't need an alignment. Remember, the term wheel alignment is a misnomer. You aren't aligning the wheels; you are aligning the suspension. Most times changing the wheels doesn't require a wheel alignment.

What is scrubbing of TYRE?

Avon Tyres Motorsport recommends that a standard scrubbing in procedure be used whenever possible (conditions and regulations allowing). This consists of subjecting the tyres through one gentle heat cycle, gradually loading them up whilst avoiding drifting the car.

Does offset affect driving?

Offset and its effects

Altering offsets affect how much load each of the two wheel bearings see both in straight-line driving and during cornering. Production-based race cars like the CRX and Integra that run stickier tires and less positive offset, exhibit somewhat high-bearing loads.

How does offset affect steering?

Clearance and a wider stance is good, however things can get interesting when it comes to steering performance. A wide wheel with lots of negative offset will move everything away from your steering axis, creating a higher scrub radius.

What's the difference between positive and negative caster?

Positive caster is when the vehicle's wheel (and lower pivot point) is in front of the upper pivot point. Negative caster has a lower pivot point behind the upper pivot point, and zero caster means the steering axis is perpendicular to the ground.

What is positive and negative camber?

Camber is described as negative when the top of the tires tilt inward. Consequently, when the top of the tires tilt away from the vehicle it is considered positive. Camber is used to distribute load across the entire tread.

What is positive caster and negative caster?

A positive caster positions the lower ball joint in front of the upper ball joint or strut mount. This results in the tire contact patch hitting the ground in front of the steering system. On the other hand, a negative caster positions the lower pivot point behind the upper pivot point.

Is positive or negative Offset better?

If your offset is too positive, you risk the inside of the tire hitting your suspension. To fix this, bring the offset down, so it's closer to zero. This moves the tire out. If your offset is too negative, then the outside of the tire will rub on the car's body and fenders.

Do positive Offset wheels stick out?

So if you put a +15mm offset wheel on the car, the wheel is likely to stick out about 1 inch. If you've ever noticed a lifted truck or a low rider with wheels sticking out, its because the offset of the rim is very low and in many cases so low that they are negative offsets.

How much Offset difference is OK?

If the new wheels are the same width, the new offset should ideally be within 5mm of the old offset in either direction. If offset must be substantially different, avoid using more positive offset at all costs. If the new wheels are wider, backspacing must be calculated.

Do wheel spacers affect scrub radius?

Wheel Spacers Increase Scrub Radius

In short, the scrub radius has a profound effect on how easy it is to turn the front tires of your vehicle. Wheel spacers increase the scrub radius as the tire track becomes wider, making your vehicle less maneuverable.

Do spacers improve handling?

There is a popular misconception that wheel spacers improve handling characteristics on sports cars because of this wider track. While there might be a slight cornering advantage due to the change in suspension geometry, the negatives far outweigh any benefits.

Does negative offset affect turning radius?

Offset really doesn't effect turning radius unless your tire is now rubbing on something.

Is ET positive or negative offset?

Most front wheel drive vehicles have positive ET wheels. Zero Offset wheels have their mounting face even with the center line of the wheel and are by definition “ET 0″. Negative Offset wheels have their mounting face toward the rear of the wheel – powerful rear-wheel drive cars often have wheels with negative offset.

Is negative offset better for off road?

By installing negative offset rims, you will push the wheel outwards and away from the suspension. Negative offset will also give a wider wheel track which can make your vehicle slightly more stable.

Does negative offset push wheels out?

You can see how a positive offset will tuck the assembly further under the fender, while a zero or negative offset pushes the wheel out towards or even past the fender.