To obtain a friction coefficient almost equal to that of a road face and measure a brake force and a speed close to true values, by bonding a highly abrasion-resistive aggregate to an outer circumferential face of a roller by a binder of high holding performance.

In measuring a brake force of an automobile, right and left wheels are set on a pair of composite testers A. Driving rollers 1, 1 are rotated at a constant speed by driving motors in right and left driving boxes 5, 5, thereby rotating the wheels. The brake force is measured by braking the automobile. When the tester is used as a speedometer tester, driving wheels of the automobile are placed and driven by an engine of the automobile, and a revolution number of the driving roller 1 is measured, whereby a speed of the automobile is calculated. An aggregate 2 of emery provided at an outer circumferential face of the driving roller 1 comes in touch to bite a tire, so that a friction coefficient close to that of an asphalt-paved face is obtained. The emery used for the aggregate 2 has high abrasion resistance and an epoxy resin used for a binder 3 has high holding performance, and therefore an outer diameter of the roller is not abraded and stable. The speed can be measured correctly.