| 摘要 |
A brake system for braking a rotatable brake disk includes a primary brake piston engagable with the brake disk and a secondary brake piston engagable with the primary brake piston and operable to move the primary brake piston into engagement with the brake disk. Both pistons are operable in response to fluid pressure. A primary brake valve controls communication of fluid pressure to the primary brake piston. A secondary brake valve controls communication of fluid pressure to the secondary brake piston.
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