How does the tire width affect driving behavior?

Posted on by admin

Table of contents

How does the tire width affect driving behavior?

accesories

tire

How does the tire width affect driving behavior??

How does the tire width affect driving behavior??
How does the tire width affect driving behavior??

The Suzuki GSX-R 750 was born eleven years ago with a 140 millimeter wide rear tire – a sensation at the time, as all athletes, with the exception of a few big bikes, rolled on 120 or 130 slippers.

02/25/2003

The Suzuki GSX-R 750 was born eleven years ago with a 140 millimeter wide rear tire – a sensation at the time, as all athletes with the exception of a few big bikes rolled on 120 or 130 slippers. In 1989, the year the Kawasaki ZXR 750 was born, a 170 tire was the measure of all things and of course the new green superbike was equipped with it. A year later, the GSX-R 1100 went one better with 180 millimeters. In the meantime, the front tires on some models had grown to a width of 130 millimeters, which five years earlier was still considered a sporty format on rear wheels.

Honda and Ducati opened the current final round in this arms race in 1994: a 190/50 rind on a six-inch wide rear wheel rim adorns the RC 45 and the 916, and since 1995 also the new superbikes GSX-R 750 and ZX-7R from Suzuki and Kawasaki. So the tires of the sports motorcycles got wider and wider, but gradually the physics seem to be setting the limits.

“respect”, says every 500 Grand Prix driver or Superbike World Championship driver. In their racing classes, the rear tire width leveled off between 180 and 185 millimeters years ago. Only in exceptional cases, on routes such as Zeltweg with many fast corners, is a 190 tire fitted in order to counteract the abrasion with more rubber with the largest possible tire contact area.

Attempts with 200 millimeter wide slippers were given up again because they hardly require any inclines to be achieved: In the curve, a motorcycle is supported against the centrifugal and weight forces by means of a force that lies on the line between the center of gravity and the tire contact point. With the same cornering speed and the same curve radius, the wider the tire, the more a motorcycle has to be angled, since the tire contact point moves further and further away from the center of the vehicle towards the inside of the curve.

But the greater inclination required is not the only disadvantage. Disturbing forces from bumps or steps in the road surface, which act on the off-center tire contact point, can cause wobbly driving behavior, especially on poor country roads. The new GSX-R 750 had to accept the following criticism in the conclusion of the individual test (MOTORRAD 26/1995): “The tires, which react sensitively to uneven ground, are really annoying in everyday operation.” Reason enough for MOTORRAD tire specialist Werner Koch to upgrade the rear of the Suzuki to 180/55 tires and a 5.5 inch wide rim produced by PVM in no time at all.

Incidentally, the number 55 expresses the ratio between tire width and height in percent: The height is 55 percent of the tire width, so theoretically 99 millimeters. In practice, however, the manufacturers usually use the maximum tolerance limit for the tire specifications due to the visual effect, for example the actual width of a 180/55 tire on a 5.5 inch wide rim is between 182 and depending on the brand 186 millimeters. The Pirelli Dragon MTR02s of dimensions 180/55 and 190/50 used in this comparison measured 185 and 194 millimeters.

After all, these nine millimeters showed an effect: “It runs more easily around tight bends, the tilt on an undulating surface is almost gone. For the country road, the combination 180/55 on a 5.5 inch rim is the much better choice”, noted tester Werner Koch in the logbook of the GSX-R. The only thing that the Suzuki has not lost is its sensitivity to ruts, even with the narrower tires. The contour of the front tire is more likely to play a decisive role here.

The alternative tires on the racetrack caused a real surprise: As expected, the Suzuki was more maneuverable when turning, but even when accelerating out it remained more stable on course than with the original tires despite the slightly smaller tire contact area. This is due to the far outward tread of the 190 tire: When accelerating in an inclined position, there is such enormous pressure on the outer edge of the tread and on the sidewalls that the tire gives way and collapses in this area. A constant pumping of the hindquarters is the result. This unrest has disappeared with the narrower 180 tire, and that’s why it also wins the race track classification.

At least as far as the growth in width of the front tires is concerned, common sense triumphed over public-appeal optics a few years ago, and people are usually content with a width of 120 millimeters. At the front, the tire contact point moving outwards has the additional disadvantage that enormous steering torques occur when braking in an inclined position. The few motorcycles that are still delivered with a 130 mm front tire are regularly criticized because of their strong positioning moment, which pushes man and machine to the outer edge of the bend.

The blue silhouette shows a driver with wide tires, the red shadow a biker with narrow tires: the wider the tire, the more lean angle is necessary for the same cornering speed and radius.


How does the tire width affect driving behavior?

Tire width and lean angle
In an inclined position, the weight G and centrifugal force F act in the common center of gravity S of the driver and the machine. A state of equilibrium is reached when the resulting force R intersects the imaginary connecting line between the contact points A of the front and rear tires. The inclination angle a that occurs lies between the vertical and the connecting line between A and the center of gravity S. Since the tire contact point A is not in the middle of the vehicle, but moves towards the inside of the curve by the amount r, the motorcycle must also adjust the correction angle, which increases with the tire width g be inclined. This correction angle and the angle of inclination a together result in the actual lean angle d between the vertical and the center of the vehicle.

Leave a Reply

Your email address will not be published. Required fields are marked *