Examkin

Soru

Zorluk: ZorBraking Systems

In a combination valve on a front-disc and rear-drum braking system, what is the primary function of the metering valve?

  1. A
    It limits hydraulic line pressure delivered to the rear brakes during rapid stops to prevent wheel lockup.
  2. It delays fluid pressure to the front disc brakes until the rear brake shoes overcome return spring tension.Cevap
  3. C
    It maintains a slight residual pressure in the hydraulic lines to keep air from entering the wheel cylinders.
  4. D
    It senses pressure drops between split hydraulic circuits and triggers the instrument panel warning light.

Cevap

The metering valve delays fluid pressure to the front disc brakes until the rear brake shoes overcome return spring tension.
Because disc brake pads have zero clearance from the rotor while drum shoes must push against return springs to reach the drum, disc brakes apply faster. The metering valve (hold-off valve) prevents fluid flow to the front disc calipers until hydraulic pressure builds sufficiently to overcome the rear drum springs, ensuring balanced initial braking.

Adım Adım Çözüm

1
Analyze the mechanical differences between disc and drum brake actuation
Disc brake pads sit directly against the rotor and apply instantly with fluid movement, whereas drum brake shoes must first overcome return spring tension and travel through clearance to reach the drum.
Without timing correction, front disc brakes would engage significantly before the rear drum brakes during light pedal application.
2
Identify the specific valve component that regulates this initial timing difference
The metering valve (hold-off valve) blocks hydraulic pressure to the front disc calipers until line pressure reaches approximately 75 to 125 psi.
This slight pressure threshold ensures the rear shoes make contact with the drums so all four wheels begin braking at the same time, preventing front-end dive.

Anahtar Kavram

Hydraulic timing and balance between disc and drum brake assemblies via the metering valve
Tahmini Süre:1m 0s
Bu soruyu puanla

Konular

Braking Systems

Bu konudan daha fazla soru