The displacement of brake parts and values for brake drag were monitored during bench testing in coasting-down mode. In this mode, the brake-drag measurement process is preceded by a brake operation process while the vehicle is running warm, and at this time the brake disks undergo heat deformation as their temperatures rise. The subsequent brake-drag measurement process involves a reduction in disk temperature. This is accompanied by a return of the disk from its heat-deformed state so that the disk approaches more closely to the inner pad, and when it impinges on the pad, drag occurs. Also, when the inclination of the inner brake pad to the brake disk at that time is such that there is less clearance between the disk and the pad on the rotation input side (leading side) and there is more clearance on the rotation output side (trailing side), the pad is drawn toward the disk so that the drag suddenly increases. This force that draws the pad and disk together is the force of the vacuum pressure generated between them. This force was successfully used to both stabilize and reduce brake drag by establishing a setting that balances the load from the pad return spring, which is a structure for the purpose of reducing drag, between the leading side and trailing side, and by establishing guidelines for the amounts of caliper piston rollback and caliper body deformation.
Article of Honda R&D Technical Review Vol.26 No.2 (229 - 236)