How can I tell if the brake camshaft is abnormal while the vehicle is running?

Performance: When applying the brakes at the same speed, it takes longer for the vehicle to stop (e.g., the normal braking distance of 30 meters is now more than 40 meters), or it takes more force to press the pedal to achieve the same braking effect.

Abnormal braking performance: a direct reflection of the working condition of the camshaft 
1. Significant decrease in braking force / longer braking distance 
Performance: When applying the brakes at the same speed, it takes longer for the vehicle to stop (e.g., the normal braking distance of 30 meters is now more than 40 meters), or it takes more force to press the pedal to achieve the same braking effect.
Reason: The camshaft is worn out, resulting in insufficient lift to push the brake shoes, a decrease in the area where the brake shoes fit the drum, and a decrease in braking force.
Emergency judgment: Test drive on a safe road at 30km/h, lightly press the brake to feel the braking force, if the pedal stroke exceeds the normal range (such as more than 2/3 of the total stroke), it may be an abnormal camshaft.
2. Vehicle deflection when braking 
Performance: Vehicle deflects to one side when applying the brakes, and the steering wheel automatically deflects to a certain direction (e.g., the front end of the vehicle deflects to the right when braking to the left).
Reason: The camshafts of the left and right wheels are worn differently, resulting in uneven braking force between the two sides (the difference is more than 15%).
Typical scenarios: High-speed driving (more than 60km/h) when the runaway is more obvious, may be accompanied by abnormal wear of tires (one side of the tread wear faster).
Rattling and abnormal vibration: visual sign of wear or stalling 
1. Squeaking or clicking sound when braking 
Sound characteristics: Sharp friction sound when stepping on the brakes, disappearing after releasing the pedal; or irregular “clicking” sound at the chassis when driving. "The sound is irregularly heard at the chassis while driving, and varies with vehicle speed.
Possible causes: 
The camshaft surface is worn and burrs are produced, rubbing abnormally against the brake shoe friction pads.
Camshaft journal wear leads to excessive clearance, shaking and hitting the bushing during operation.
Self-inspection method: after stopping the car to observe the brake drum gap, if you find metal shavings or sludge mixture, may be the product of wear.
2. Pedal vibration or rebound abnormality 
Performance: the pedal has obvious shaking when stepping on the brake, or the pedal slowly rebound after releasing the pedal (normal should be quickly reset).
Reason: camshaft stagnation or deformation, resulting in delayed reset of the brake shoe, pedal return resistance increases.
Abnormal Vehicle Condition: Indirectly Reflecting Camshaft Failure 
1. Brake Drums Overheating or Smoking 
Performance: Touch the brake drums after stopping the vehicle (be careful to avoid scalding), if the temperature of one side is significantly higher than that of the other wheels (the temperature difference is more than 50°C), or if you see smoke coming out of the drums.
Reason: camshaft wear leads to brake shoes stuck in half-braking state, continuous friction heat.
DANGER ALERT: If the temperature exceeds 300℃, it may cause the brake drum to crack, so stop the vehicle immediately to cool down and check.
2. Abnormal tire wear 
Symptoms: The inner or outer tread of one wheel is severely worn, jagged or unilateral.
Associated cause: camshaft failure leads to continuous light braking of the wheel and increased friction between the tire and the ground.
Abnormal Performance under Special Working Conditions: The “Litmus Test” for Hidden Failures 
1. Faster Decline in Braking Power when Continuously Descending a Slope 
Scenario: After continuous use of the brakes on mountainous road sections, the braking power is obviously weakened, and it is necessary to step on the brakes more frequently in order to control the vehicle's speed.
Reason: The deformation of the worn camshaft increases under high temperature, and the brake shoe opening strength decreases, which triggers heat recession. 2.
2. Increased risk of skidding when braking on wet roads 
Performance: When braking on rainy or icy roads, the vehicle is more prone to skidding or tailgating, and the steering wheel is difficult to control.
Reason: camshaft wear leads to uneven braking force between the left and right wheels, and the probability of skidding on low traction surfaces increases significantly (the risk increases by 2-3 times when the difference is more than 10%).
Simple test with the car: preliminary judgment without professional tools 
1. Observe the consistency of the brake arm action 
Operation: Get an assistant to step on the brake, and observe the swinging amplitude of the brake arm of each wheel under the car.
Judgment criteria: under normal circumstances, the swing angle of the brake arm should be consistent (error ≤ 5 °), if a wheel brake arm swing amplitude is significantly smaller, it may be the camshaft wear caused by insufficient lift.
2. Check the free travel of the brake pedal 
Operation: Use a straightedge to measure the height of the pedal when it is not pressed down, gently step on the pedal until you feel resistance, and measure the change in travel.
Standard range: The free travel is usually 20-30mm, if it exceeds 40mm, the camshaft may be worn or the clearance of related parts is too large.
Emergency Response and Maintenance Suggestions 
1. Steps for Handling the Abnormalities Discovered 
If you find that the brakes are running out of alignment or the braking force is significantly reduced while driving, immediately turn on the dual flashers, reduce the speed of the vehicle, and choose a safe area to stop the vehicle.
Check the temperature of the brake drum after stopping the vehicle. If one of the wheels is overheated, try to push the brake arm manually (gloves are required); if there is a lot of resistance or it cannot be reset, the camshaft may be stuck.
Avoid further driving, contact a service professional, and use the engine brake to assist deceleration on the way.
2. Regular Preventive Inspection 
At every 5000km service, measure the clearance between the camshaft and the bushing with a tape measure (standard value 0.05-0.1mm, over 0.3mm needs to be replaced).
Every year, disassemble the brake drum and visually inspect the camshaft surface for scratches and wear grooves (more than 0.2mm in depth needs to be ground or replaced).