9.8 Remove the specimen and reweigh to the nearest 0.001 g (0.0001 g for Procedure C).
9.8.1 Wear Scar—Observe the wear scar and compare it to the photographs of uniform and nonuniform wear scars in Fig.11. A nonuniform pattern indicates improper alignment of the rubber rim to the test specimen or an unevenly worn rubber wheel. This condition may reduce the accuracy of the test.
9.9 Preparation and Care of Rubber Wheels—Dress the periphery of all new rubber wheels and make concentric to the bore of the steel disk upon which the rubber is mounted. The concentricity of the rim shall be within 0.05 mm (0.002 in.) total indicator reading on the diameter. Follow the same dressing procedure on used wheels that develop grooves or that wear unevenly so as to develop trapezoidal or uneven wear scars on the test specimen (Fig. 11). The intent is to produce a uniform surface that will run tangent to the test specimen without causing vibration or hopping of the lever arm. The wear scars shall be rectangular in shape and of uniform depth at any section across the width. The rubber wheel may be used until the diameter wears to 215.9 mm (8.50 in.). New rubber rims may be mounted on steel disks by the qualified source (6.2).