What could cause a brake pedal to feel extremely hard when stopping in a vehicle with hydraulic brakes?

A brake pedal feeling extremely hard when stopping is typically indicative of an issue with the brake booster, which is a critical component in the hydraulic braking system. The brake booster helps amplify the force exerted by the driver on the brake pedal, allowing for more effective braking with less effort.

When the brake booster is faulty, it may fail to provide the necessary assistance, resulting in a pedal that requires significantly more force to depress. This can create a sensation of the brake pedal being excessively hard or stiff. Common signs of a faulty brake booster include a hard pedal, especially when the engine is off, or increased effort needed to engage the brakes.

The other options relate to different braking system problems. Bad brake pads might cause issues like noise or reduced stopping power, but would not typically result in a hard pedal feel. A weak brake shoe return spring could lead to dragging brakes or uneven wear, but wouldn’t affect the pedal feel in a hydraulic system. Air in the brake lines usually leads to a spongy or soft brake pedal feel due to the compressibility of air, which contrasts with the symptoms described. Therefore, the brake booster is directly tied to the sensation of a hard brake pedal.