This problem does not occur when measurements are carried out on stationary tyre test benches. In this case the tyre which is kept stationary, is brought in contact with a movable rolling surface area. The data is acquired by power sensors mounted on links holding the wheel. Three types of rolling surface areas are used for these applications: - A roller with outer bearing surface,
- A roller with inside bearing surface,
- A smooth band moved by two rolls.
A frequently used and cost-effective method of testing tires involves the roller test bench with outer bearing surface. Besides the high loading capacity and compactness, the large space offered on the wheel allows various wheel guide concepts and wheel positions as well as convenient tyre mounting.
Due the effect of the centrifugal force, it is difficult to fix the different road surfaces onto the roller. Tests with a wet tyre tread are only partially possible.
The effect of centrifugal force on the other hand supports the fixing of the tyre tread pavement in test benches with inner bearing surfaces. Hence, this test bench is especially suitable when measurements involve differing road surfaces and to determine the wet rolling behaviour of the tyre. The limited space on the wheel complicates tyre mountng and wheel control.
Measuring errors result in all roller test benches due to the cylindrical profile of the bearing surface. In contrast to flat roads, the tyre contact area and the deflection extends at the same load. The result is increasing frictional and flextural resistances. The error can be minimised by roller radii which are relatively large compared to the wheel radius. Correction factors have to be introduced in order to apply the measurement results for flat roads.
Flat track test benches realize a smooth rolling surface to a large extent. Besides they offer unlimited space for wheel control and wheel motions as well as for tyre mounting. By the change of band, changed road surfaces can be realized within certain limits. In the same way wet running tests are possible. Belt guidance by rolls, however, requires a large technical expense since bearing surface vibrations can produce measurement errors. Furthermore band abrasion increases the running costs.