the shim plates 53 63 in this modification tile lower portions 52d 62d of backing plates are cut away in such a manner that the backward side end faces of backing plates 52 62 are protruded at their upper portions in fig8 c the backward torque receiving portion 30b of caliper member 30 is formed at its upper portion with projections 30b1 for engagement with the backward side end faces of backing plates 52 62 without forming any projection on the side end faces of backing plates 52 62 in these modifications the backing plates 52 62 are applied with a rotational force in a direction shown by an arrow respectively in the figures when drawn backward and engaged with the backward torque receiving portion 30b in braking operation in addition the disc brake assembly of the present invention may be modified as shown in fig9 a to 9 c in fig9 a the first shim plates 53 63 of friction pad 50 60 are formed with side lugs 53a 63a respectively at their lower portions without forming the side lugs 53a 63a at their upper portions in fig9 b the backward side end faces of backing plates 52 62 are formed with side projections 52e 62e respectively at their lower portions without providing the first shim plates 53 63 in fig9 c the backward torque receiving portion 30b of caliper member 30 is formed with projections 3062 for engagement with the backward side end faces of backing plates 52 62 without providing tile first shim plates 53 63 in these modifications the backing plates.