If your vehicle is showing rhythmic thumping or beating noise when slowing down, here are the most likely causes and the parts you'll need to fix each one.
If the lug nuts were not properly torqued after a recent tire change or brake job, the wheel can wobble on the hub. This creates a heavy, rhythmic thump that becomes extremely noticeable and dangerous when slowing down.
Unevenly worn or warped brake rotors cause the brake pads to grab and release rhythmically. This creates a beating noise and a noticeable pulsation when applying the brakes to slow down.
A tire with an internal steel belt separation, severe cupping, or a flat spot will create a rotational thumping noise. This sound often becomes more pronounced when slowing down as the vehicle's weight shifts forward onto the front tires.
Degraded rubber suspension bushings allow the control arm to shift back and forth under braking forces. This can cause a rhythmic clunking or thumping as the suspension rapidly loads and unloads while decelerating.
If caliper bracket bolts are left loose or hardware is missing after a brake job, the brake caliper can shift and bang against the mounting bracket rhythmically as the rotor turns and grabs the pads.
On rear-wheel or all-wheel drive vehicles, a failing U-joint or driveshaft center support bearing can cause a heavy thumping noise under the floorboards when decelerating, as the driveline tension unloads.