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Flat spots (brake-flatting) > < Useful information regarding tyre noise

A5

Saw-tooth wear
Saw-tooth wear
Saw-tooth wear is a stepped wear pattern on the individual tread blocks – see illustration – that can cause increased tyre noise. The saw tooth pattern ("heel-and-toe" wear) is caused by uneven deformation of the tread blocks in the tyre contact area. Saw-tooth wear is more pronounced on non-driven wheels than on driven wheels.
New tyres are more susceptible to saw-tooth wear because of the greater elasticity of the high tread blocks. As the tread depth decreases, the tread blocks become more rigid and the tendency to wear in a saw-tooth pattern decreases.
What does a saw tooth wear pattern look like?
Viewed in the direction of travel, the tread blocks are higher at the front than they are at the rear, see illustration. Pronounced saw-tooth wear can lead to customers complaining about tyre noise.
Pronounced saw-tooth wear occurs:
t  when toe-in values are too high
t  when tyre pressures are incorrect
t  when the tread is coarse, open
t  on tyres which are fitted to the non-driven wheels
   
t  when the vehicle is driven very fast around tight corners
1 - More pronounced wear at the front of the tread block
2 - Direction of rotation
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 has 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 greater immediately after the tyres have been interchanged, but will return to the normal level after driving about 500 – 1,000 km.
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, turn both tyres around 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.
Saw-tooth wear is a normal wear pattern and can be rectified on non-directional tyres by rotating the wheels diagonally. The wear should then be compensated after approx. 500 – 1,000 km.
The complaint report should include information detailing the previous repair work.
Modern tyres are designed for maximum driving safety, even in wet conditions. This demands an open tread pattern at the shoulders of the tyre and a softer rubber composition for the tread itself, both of which accelerate saw-tooth wear.
Saw-tooth wear is a normal wear pattern and does not constitute a fault which is covered by the warranty.
  N44-0235

Flat spots (brake-flatting) > < Useful information regarding tyre noise