| Locking points are the result of sharp braking with the wheels locked, causing friction to the rubber on the tyre where it is in contact with the road. |
| As the tyre slides over the road surface, the friction generates heat which reduces the resistance to friction of the tyre tread. |
| Even the use of a combination of friction resistant materials on the tyre rolling surface does not exclude the possibility of locking points, such as those produced during severe braking. |
| Even regulated ABS braking systems are unable to prevent a short period of locking and the resultant reduced planning. |
| The significance of this friction chiefly depends upon the vehicle speed, the road surface and the load on the wheels. The numerical examples given below serve to illustrate the above. |
| For a vehicle braking on a dry road, with the wheels locked, until coming to a total standstill, the friction of the rubber in the contact area, approximately the size of a postcard, is approximately: |
| t
| at 57 km/h = 23.8 m braking distance, to 2.0 mm |
| t
| at 75 km/h = 41.8 m braking distance, to 3.3 mm |
| t
| at 92 km/h = 71.6 m braking distance, to 4.8 mm |
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