Get Facts about wheels and tyres (commercial vehicles) -> Tyre noise Guide for Volkswagen Caddy SUV Third Generation (2003-2015)

Amarok 2011 ➤ , Caddy 2004 ➤ , Caddy 2011 ➤ , Caddy Kasten/Kombi 1996 ➤ ...

Wheels and Tyres Guide - Edition 01.2011

4.2.11

Diagonal washout

Diagonal washout on a tyre

Diagonal washout runs at an angle of approx. 45° to the direction

of rotation.

It usually occurs at one point only, but can also occur at several

points around the circumference of the tyre.

Washout occurs almost exclusively on the tyres on the non-driven

wheels, in particular at the rear left. Washout occurs very often

on some models, while it poses no problem at all on other models.

The effect is intensified by high toe-in values. Toe-in values in the

region of the lower tolerance limits of the specified alignment val‐

ues improve the wear pattern.

The most pronounced diagonal washout is often found in the area

where the tyre components are joined.

Wheels with positive toe-in roll with a slip angle even straight

ahead. This leads to a diagonal stress in the contact patch or

footprint on the tyre/road surface.

This wear pattern is intensified when tyre pressure is too low. To

avoid such tread wear patterns, the toe-in values of the two rear

wheels should be identical and the specified tyre pressures ob‐

served.

If you detect washout, you should fit the wheels on the driven axle,

assuming the washout is identified at an early stage. Deeper

washout cannot be repaired.

Faulty adjustment

If a customer complains of „diagonal wear spots“, the toe adjust‐

ment must be examined. If toe-in is correct, the cause of the

diagonal washout is very probably the tyre itself.

Tyres with diagonal washout caused by incorrectly set axle ge‐

ometry at the wheels are not covered by warranty.

4.3

Tyre noise

4.3.1

General notes on tyre noise

Tyre noise that can be heard by the human ear is caused by vi‐

brations which are transmitted by the air from the source of the

sound to our ears.

Of interest here are the noises caused by certain characteristics

and effects while the tyres are rolling (source of the sound).

The cause of the noise is largely dependent on the combination

of the road surface and tyres.

The structure and material of the road surface will greatly affect

tyre noise. For example, the noise level on a wet road is much

higher than on a dry road.

The pattern of the tyre tread also has a significant influence on

tyre noise. Tyres with transverse grooves at a 90° angle generate

more noise than tyres with grooves running diagonally.

Small tread blocks are unstable. Their highly pronounced defor‐

mation agitates the air as the tyres roll. This creates the air

vibrations that cause tyre noise.

Wider tyres are louder. They need more tread channels to dis‐

place water. When they are rolling, these tread channels displace

the air, also creating air vibrations.

Rep. gr.44 - Wheels, tyres, vehicle geometry

Amarok 2011 ➤ , Caddy 2004 ➤ , Caddy 2011 ➤ , Caddy Kasten/Kombi 1996 ➤ ...

Wheels and Tyres Guide - Edition 01.2011

Further effects that also influence tyre noise:

♦ „Tyre vibration“ is the principal cause of tyre noise. It is caused

by the columns of air in the tread channels being agitated._lk

♦ „Air pumping“ is the compression and expansion of the air

caused by the deformation of the tread blocks as the tyre con‐

tact patch moves along the road surface.

Useful information regarding tyre noise

Tyre noise is determined primarily by the tyres and the road sur‐

face.

The coarseness, structure and material of the road surface influ‐

ence tyre noise.

The widths of the tyre and the rim, among other things, influence

tyre noise. Due to their larger contact area, wider tyres will cause

more tyre noise than narrow tyres, as more air has to be displaced

and more „mass“ is agitated to create vibrations.

A wider wheel rim will also cause a tyre to have a wider contact

patch. The effect on tyre noise is thus very similar to that of a wider

tyre. Moreover, the damping characteristics of the tyre may also

be adversely affected by the wider wheel rim.

Tyre noise is more perceptible in the passenger compartment of

vehicles with front-mounted engine as wind and engine noises

are harder to hear in the rear.

4.3.2

Saw-tooth wear

Saw-tooth wear is a stepped wear pattern on the individual tread

blocks ⇒ page 28 that can cause increased tyre noise. The saw

tooth is caused by uneven deformation of the tread blocks in the

tyre's contact patch. Saw-tooth wear is more pronounced on non-

driven wheels than on driven wheels.

4. Facts about wheels and tyres (commercial vehicles)

Amarok 2011 ➤ , Caddy 2004 ➤ , Caddy 2011 ➤ , Caddy Kasten/Kombi 1996 ➤ ...

Wheels and Tyres Guide - Edition 01.2011

New tyres are more susceptible to saw-tooth wear because of the

greater elasticity of the high tread blocks. As the tread depth de‐

creases, the tread blocks become more rigid and the tendency to

wear in a saw-tooth pattern decreases.

Appearance of saw tooth

A - Tread block of a new tyre; seen in direction of motion

-arrow 1-, tread blocks are equally high in front and back.

B - Development of saw teeth; seen in the direction of rotation

-arrow 1-, tread blocks are higher in front than in back -arrow 2-.

C - Seen in the direction of rotation -arrow 1-, tread blocks show

greater wear in the front section of the „saw tooth“ -arrow 3-.

Pronounced saw-tooth wear can lead to customers complaining

about tyre noise.

Pronounced saw-tooth wear occurs under the following condi‐

tions:

♦ toe values are too high

♦ tyre pressures are incorrect

♦ tread is coarse and open

♦ tyres are fitted on the non-driven axle

♦ very fast cornering.

non-directional tyres

In the event of saw-tooth wear, the direction of rotation of the tyre

must be reversed. If saw-tooth wear is especially pronounced and

tyre noise is increased, interchange the tyres diagonally. This will

reduce the saw-tooth effect.

On front-wheel-drive vehicles, this effect is intensified by the

greater wear on the front axle.

Tyre noise will be somewhat louder immediately after the tyres

have been interchanged but will return to a normal level after

about 500…1,000 km have been driven.

Directional tyres

In the event of increased saw-tooth wear on the rear tyres – in

particular on front-wheel drive vehicles – interchange the front and

rear tyres. In the event of increased saw-tooth wear on the outer

edges of the tyres on one axle, reverse both tyres on their rims.

The left-hand wheel must then be fitted on the right side of the

vehicle and the right-hand wheel on the left side.

4.3.3

Flat spots (from locking wheels)

Flat spots can result from an extreme brake application which

causes the wheels to lock, so that the rubber is worn off at the

contact patch between the tread and the road surface.

As the tyres slide over the road surface, friction generates heat,

which also reduces the wear resistance of the tread material.

Not even a highly wear-resistant tread compound can prevent the

flat spots caused by violent braking.

Even ABS-controlled brake systems cannot prevent brief locking

of the wheels, and thus, minor flat spots.

The degree of such wear depends largely on the vehicle speed,

the road surface and the load placed on the wheel. The following

examples should make this clear.

Rep. gr.44 - Wheels, tyres, vehicle geometry

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