Tires, Rolling Noises - Audi 100 1991 Repair Manual

Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Wheel and Tire Guide - Edition 11.2010
The axle alignment log should be included with the tire complaint.
Tires with diagonal wear spots which developed due to faulty ad‐
justment of the axle geometry are excluded from the warranty.
1.13.9 Changes to the Suspension
If a "lowering-kit" and /or light alloy wheels from accessories which
have not been approved by Audi are used, wheel alignments
which deviate from the alignment specified in design may occur
during travel.
Even if the adjustment of the axle geometry measured on a stand‐
ing vehicle is correct, changes in the body height and positions of
the wheels during travel can lead to changes to the paths of travel
of the wheel suspension.
For this reason, uneven wear is pre-programmed.
1.14

Tires, Rolling Noises

⇒ "1.14.1 General Information", page 30
⇒ "1.14.2 Rolling Noise, Causes", page 30
⇒ "1.14.3 Heel and Toe Wear", page 31
⇒ "1.14.4 Wear Spots", page 32
1.14.1 General Information
Rolling noise perceived by the human ear is caused by vibrations
transmitted from the noise source to the ear via the air.
Here we are interested in noises created by certain characteristics
of the tires as well as the effects of rolling (noise source).
The cause for the noise generation depends primarily on the
combination of road surface and tire.
The surface structure and material of the road surface also have
a strong influence on the rolling noise. For example, the noise
level on a wet road is substantially higher than on a dry road.
The design of the tread has a great influence on the noise gen‐
eration. Tires with cross grooves at an angle of 90° are louder
than tires with grooves running diagonally.
Small tread blocks are unstable. Due to strong deformation, the
air is excited by the rolling tires. Air vibrations occur, which will
generate noises.
Wider tires are louder. They require more tread grooves for water
displacement. Air is displaced by these tread grooves while roll‐
ing, which also cause air vibrations.
Other effects which also have an influence on noise generation:
♦ »Tire vibration« is the main cause of rolling noise. The noise
is generated by the excitation of the air column in the grooves.
♦ »Air pumping« is the compression and expansion of air as the
contact patch comes in contact with the road surface and the
tread blocks are deformed.
1.14.2 Rolling Noise, Causes
Noise generation is created chiefly by tires and the road surface.
Influencing factors of road surface are roughness, structure and
material.
Influencing factors for tires fall under different tire and rim widths.
A wider tire generates more noise due to its wider contact patch
30
Rep. Gr.44 - Wheels, Tires, Wheel Alignment
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