General information about rolling noise
Rolling noise, perceived by the human ear, is vibrations emanating from a sound source and reaching the ear through the air.
Interesting here are the noises that arise due to certain features, as well as the effects when rolling tires (noise source).
The cause of the noise largely depends on the combination of tires and road surface.
Surface structure and roadway material also have a strong influence on rolling noise. The noise level on a wet road, for example, is much higher than on a dry one.
Profiling the tread pattern greatly affects the noise level. Tires with 90°transverse grooves are noisier than tires with diagonal grooves.
Small tread blocks are unstable. Due to their strong deformation, air is shaken when the tires roll. Air vibrations are created. which lead to noise.
Wider tires are noisier. To drain water, they must have more grooves. During rolling, air is displaced due to these grooves, due to which air vibrations also occur.
Other effects affecting noise.
«Tire wobble» is the main cause of rolling noise. They arise due to the excitation of air columns in the grooves of the tread.
«Air pulsation» - this is the compression and expansion of air when the tire contact area hits the roadway, during which the tread blocks are deformed.
Tire noise
Noise is mainly determined by tires and road surface.
The quality of the road surface that affects the noise is the roughness (roughness), structure and material.
Tire impact parameters are, among other things, tire and rim width. A wider tire, due to the larger area of contact with the road surface, creates more noise, as more air is squeezed out and more «weight» excited in vibrations than with a smaller size.
A wider rim also increases the tire's contact area. Thus, the impact on noise is the same as with a wide tyre. In addition, wider rims have a negative effect on the damping properties of the tire.
Tire rolling noises are audible in cars where the engine is installed in the front, better in the rear seats, since aerodynamic noise and engine sound are less disturbing in this part of the cabin.
Sawtooth tread wear
Tread wear in the form of a sawtooth track is a stepped wear of individual tread blocks, which can lead to increased noise. Sawtooth wear occurs due to uneven deformation of the tread blocks on the contact surface of the tire with the road surface. This type of wear is more common on non-driving wheels than on driving ones.
Newer tires are more prone to sawtooth tread wear because high tread blocks are more elastic. As the tread depth decreases, the stiffness of the tread blocks increases, and the tendency to this type of wear decreases.
A - New tire tread blocks; The tread blocks, as seen in the rolling direction arrow 1, are the same height front and rear.
B - Tread wear in the form of a sawtooth track; The tread blocks, when viewed in the direction of rolling arrow 1, are higher at the front than at the rear arrow 2.
C - Profile blocks, viewed in rolling direction arrow 1, have heavy wear at the front «tooth» arrow 3.
With a pronounced wear of the tread in the form of a sawtooth track, increased tire noise may become noticeable.
Pic. 4.11. Type of sawtooth wear
Severe tread wear in the form of a sawtooth track occurs when there is too much convergence, incorrect air pressure in tires with large tread blocks, tires mounted on wheels on a non-drive axle during extreme cornering.
Tires with non-directional tread pattern
If tread wear in the form of a sawtooth track is detected, the direction of rolling of the tire should be changed. If increased wear of the tread in the form of a sawtooth track and increased noise are detected, it is necessary to rearrange the wheels crosswise. This will reduce wear.
On front-wheel drive vehicles, the effectiveness of this approach will be even more noticeable due to more tire wear on the front axle.
Rolling noises will be a little stronger immediately after changing the wheels, but after a run of 500-1000 km, the normal noise level will be restored.
Tires with directional tread pattern
With increased wear of the sawtooth tread on the tires of the rear axle - mainly with front-wheel drive - the rear wheels must be moved forward. With increased sawtooth wear on the outer edges on the same axle, both tires should be turned over on the rim. After that, the left wheel should be mounted on the right side, and the right wheel on the left.
Wear spots due to driving with locked wheels
Pic. 4.12. Wear spots on the tread due to braking with locked wheels
This type of wear is a consequence of heavy braking with locked wheels, in which the tread rubber is erased on the contact area of the tire with the road surface (pic. 4.12).
When tires slide on the road, frictional heat is generated, which reduces the abrasion resistance of the tread material.
Even the most wear-resistant tread compounds are not immune to the wear spots that can form under extreme braking.
And even brake systems equipped with ABS do not exclude short-term blocking and thus little wear.
The degree of such abrasion is significantly dependent on the speed of movement, the road surface and the load on the wheel. For clarity, the following examples are given.
When braking a car with locked front wheels on a dry road surface to a complete stop, the wear of rubber on a contact area equal to a postcard will be:
- from 57 km/h = 23.8 m braking distance to 2.0 mm;
- from 75 km/h = 41.8 m braking distance to 3.3 mm;
- from 92 km/h = 71.6 m braking distance to 4.8 mm.
Tires with such damage are unsuitable for further use and must be replaced.
Causes of uneven running
The reasons for the unevenness of the course are various. Rough running can also occur due to tire wear. During operation, tires do not always wear out evenly over the entire tread surface. Because of this, a slight imbalance already appears, which interferes with the smooth rolling of a previously perfectly balanced wheel.
Such an imbalance is not yet felt on the steering wheel, but it does take place. It increases tire wear and thus shortens the service life.
Note: To ensure optimum safety, smooth running and even wear throughout the tire's life, it is recommended that the rims and tires be balanced at least twice during the tire's life.
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