The brake pedal is too large, the braking effect is slow, the braking efficiency is low or even lost, and the braking distance increases. Cause of failure: 1. The pressure of brake oil is insufficient. (brake master cylinder is short of oil, brake line ruptures, tubing joint leakage, oil line blockage). 2. There is air in the brake system. 3, brake pedal free travel or brake clearance is too large, brake shoes friction contact is not good, wear serious or oil pollution. 4, brake master cylinder, wheel cylinder piston and cylinder wear or tear, leather bowl aging damage. Troubleshooting: 1, continuously step down the brake pedal, such as the pedal gradually increase and have a flexible feeling, but after a little stop a little after stepping on the pedal is still very low, that is, there is air in the brake system, at this time the brake system should be exhaust. 2, a foot brake is not good, but continuous pedal several times when the braking effect is very good, generally for the brake pedal free travel too large or brake clearance is too large. The pedal free travel should be adjusted, then the brake clearance should be checked, and the brake should be disassembled and repaired if necessary. 3, when stepping on the brake pedal, it is not weak and unsinkable, but the brake effect is bad. This phenomenon is the wheel brake failure, such as brake shoe oil or bad contact, friction film aging, wear, brake drum wear uneven. Check the braking technology status and adjust and repair if necessary.