Tire Wear/Service Life
Tire wear/service life
General information
Numerous demands are made on a tire. See points A through H.
Each of these demands is made on every tire to a certain degree.
Depending on the use of the tire and the vehicle type, certain demands may be more heavily weighted while others are accordingly less significant.
One expects greater adhesion, even on wet or flooded surfaces from H, V and Z tires for high-powered vehicles Consequently, the service life for tires of this type is not as high as for S or T tires, for example.
Tire requirements
A - Wet braking behavior
B - Comfort
C - Steering precision
D - Driving stability
E - Tire weight
F - Service life expectancy
G - Rolling resistance
H - Hydroplaning
The pie chart represents the tires performance. It shows how the extent of the demands
A through H could be distributed in tire construction and rubber compound.
The improvement of one characteristic leads to the worsening of another one.
Example:
The improvement of wet braking behavior - A - leads to losses in comfort - B - rolling resistance - G - and service life expectancy - F -.
The service life expectancy of car tires depends not only on the rubber compound and the tire construction. The operating conditions, circumstances specific to the vehicle and the driving style all have a strong influence on the tires service life.
With modern vehicles and appropriate engines, especially gentle and economical but also extremely sporty driving is possible. Service life of 5,000 to 40,000 km and even more is possible.
Note:
^ Driving style is the decisive influencing factor on the life of the tires.
High speed tires, wear characteristics
These tires are designed for the highest speeds. Good traction on wet roads is emphasized when developing these tires. Tread compounds do not have the abrasion resistance of tires for lower speeds, such as T and H tires.
Therefore the service life expectancy of high-speed tires is substantially lower under comparable operating conditions.
Influences on the service life of the tire
The following factors influence the service life of a tire in varying degrees.
Driving style *See note
^ Speed
^ Brakes
^ Acceleration
^ Cornering
Service *see note
* More information on maintenance factors can be found
Tire pressure
Area:
^ Paving
^ Exterior temperature/climate
Vehicle:
^ Weight
^ Dynamic toe and camber values
Tire operating conditions
Speed range, wet or dry
Tire construction:
Winter/summer
Driving style
1. Constant driving without deceleration and acceleration.
Example:
2. Brakes
The highest abrasion is achieved when braking.
Example: Braking from a speed of 50 km/h.
3. Acceleration (driving style)
The slip that occurs during a gentle acceleration from a stop is approximately the same as the slip that occurs at a steady speed of approximately 100 km/h.
Example:
Cornering (driving style)
A sporty driving style and driving at higher speeds also cause greater wear when driving around curves.
In practice, this means doubling the speed in a curve leads to an increased abrasion by a factor of 16. This is the "extra charge" for driving faster.
Example: Driving around a curve with a radius of 150 m.
Maintenance (tire air pressure)
The weight of the vehicle flattens the tires contact patch. When the tire rolls, this results in deformation all around the circumference of the tread and the entire belt assembly. With low pressure, there is a greater deformation which results in more intense warming and greater rolling resistance. This all results in a greater wear and a greater safety risk.
Example: Specified series production tire pressure depending on load on cold tires
Excessive air pressure leads to greater wear at the center of the tire and reduced rolling comfort. It is recommended always to maintain the air pressure indicated by the manufacturer.
Diagram 1
Tread depth over service life for vehicles with front wheel drive and V tires
P - Tread depth
S - Distance driven
1 - Front axle
2 - Rear axle
Diagram 2:
Tread depth over service life for vehicles with all wheel drive and V tires
P - Tread depth
S - Distance driven
1 - Front axle
2 - Rear axle
Note:
^ The diagrams presented cannot be applied in general.
^ They only illustrate the wear characteristics on the front and rear axles as well as wear characteristics of front and all-wheel drive vehicles.
^ Depending on operating conditions and chassis, the service life that can be attained may deviate substantially.
As can be seen in diagrams 1 and 2, for a given distance, more tread wears off tires with a complete tread than off tires which are quite worn. After the first 5,000 km, no conclusion can be made about the total service life because the wear curve is not linear.
On front-wheel drive vehicles, the front wheels must transmit the major portion of the lateral and braking forces as well as the steering and traction forces. Due to these demands, the front tires on front wheel vehicles wear more quickly than rear tires. Even usage of all tires is achieved by regularly exchanging front and rear tires. Rotating the wheels
SA 18 - Uniformly worn tires
The demands on the tires increase constantly.
The causes are the following factors:
^ Higher vehicle weight
^ High speeds
^ Increased vehicle safety.
A high load on tires naturally causes high wear.
The driving style has a profound influence on the tire wear. Therefore, for complaints about wear when the treads are uniformly worn, the tires will not be replaced under warranty.
The actual service life of a tire can only be determined when the tread depth is 2 mm, see diagram
Measuring tread depth
Note:
^ When measuring tread depth, take measurements in the main grooves.
^ Do not measure on the TWI (tread wear indicator).
Tread depth of a tire must be measured in the main grooves at the points showing the most wear. Main tread grooves can be recognized by the TWI. The positions of the tread wear indicators are visible several times along the tire shoulder. The TWI protrusions are 1.6 mm tall. This is the minimum tread depth legally prescribed in Germany.
Different values may apply in other countries.
Tread Wear Indicators (TWI) must not be included in the measurement. The deepest point of the groove must be used for the measurement.
A - Tread wear indicators (TWIs) in main tread grooves. Items can be identified 6 times on the circumference of the tire shoulder.
B - Tread depth - P - in the main tread groove
Tread wear indicators - TWI
TWI *see note is visible 6 times on the circumference of the tire shoulder.
* TWI means: Tread Wear Indicator
One-sided wear
In many causes, this is caused by driving style, but sometimes it is also caused by incorrect axle adjustment.
One-sided wear, in conjunction with scrub marks on tread ribs and finer grooves, always appears when tires roll at an extreme slip angle and consequently scrub on the road surface.
Driving quickly around curves leads to increased wear, especially on the outside edge.
A rounded tire shoulder in conjunction with especially high wear on the outer tread bars indicates fast driving around curves. This wear pattern is influenced by the driving style.
The suspension is adjusted to certain toe and camber values to optimize handling. When tires roll under conditions other than those specified, increased and one-sided wear must be expected.
Strong one-sided wear can be caused especially by incorrect toe and camber values. This increases the danger of diagonal wear spots.
Toe-out or negative toe-in:
The distance between the fronts of the tires - A - is greater than the distance between the backs of the tires - B - - C - direction of travel).
Toe-in or positive toe-in:
The distance between the fronts of the tires - A - is less than the distance between the backs of the tires - B - - C - direction of travel).
To avoid one-sided tire wear, ensure that the wheel alignment remains within the tolerances specified by the vehicle manufacturer. The most common deviation of wheel alignment is caused by external influences, for example hard contact with the curb when parking.
A measurement of the axle geometry can determine whether the wheel alignment is within the specified tolerances or whether a correction of the wheel alignment is necessary.
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 standing 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.
SA 11: One-sided wear - adjustment error
If the complaint is about one-sided tire wear, check the axle geometry. Billing to warranty is only possible in cases of one-sided tire wear that is caused by axle geometry errors that cannot be traced back to external effects on the tires and rims. The axle alignment log should be included with the tire complaint registration.
Due to tire skew increased and one-sided wear. Frequently in conjunction with raised running surface to the point of ridge formation on tread edges.
Center wear
This wear pattern is found on drive wheels on high-powered vehicles that often drive long stretches at high speed.
At high speeds, the centrifugal force increases the tire diameter at the center of the tread more than at the shoulders of the tire. The drive forces from the center area of the tread are transferred to the road surface. This is reflected in the wear pattern.
These effects can appear especially extreme on wide tires.
Reducing the tire pressure is not an effective remedy for this wear pattern.
CAUTION!
For safety reasons, tire pressure must never be lowered below specified pressure under any circumstances.
A largely even wear pattern can be achieved if tires are changed in a timely manner from the tractive to the non-tractive axle.
Typical wear pattern of tires on the tractive axle of high-powered vehicles. The increased wear at the tread center is caused by stresses related to the centrifugal force of the tire and the transmission of traction forces.
Diagonal wear spots
Diagonal wear spots run at an angle of approx. 45° with respect to the plane of circumference. They usually occur once, but may also occur several times along the tire circumference.
Wear spots appear almost exclusively on the non-tractive tires, especially the left rear tire. There are vehicle models where wear spots appear rounded, which are not a problem. The effect is increased by high toe values. Toe values at the lower tolerance limit of the specified value improve the wear pattern.
The tire component integration is often found in the area with the most pronounced diagonal wear spots.
Wheels with toe-in roll with a slip angle even when the vehicle is traveling straight ahead. This leads to diagonal tension in the contact zone between tires/road surface.
Driving with reduced tire pressure will improve the wear pattern. To prevent such wear patterns, the toe values of both rear wheels should be the same and the specified tire pressure should be maintained.
If wear spots are detected, mount the wheels on the tractive axle if the wear spots are still in the initial stage. Deeper wear spots are irreparable.
SA 18 - Wear; SA 11 - Adjustment error
When a customer complains of diagonal wear spots, the toe adjustment must be checked. If it is OK, the cause for the diagonal wear spots is most likely in the tires. Billing to warranty is possible in this case.
The axle alignment log should be included with the tire complaint.
Tires with diagonal wear spots which developed due to faulty adjustment of the axle geometry are excluded from the warranty.