Why Does a Car Make a Thumping Sound When Driving on Rough Roads?
4 Answers
Generally, the most common source of abnormal noises on bumpy roads is the vehicle's chassis. If the chassis makes clunking sounds on rough roads, the first step is to inspect the car's shock absorbers. Based on the location of the sound, identify the problematic area. When the car is parked on flat ground, the distance between the car and the ground is too small, making it difficult to inspect for faults. It is best to visit a 4S shop or repair shop and use a lift to raise the vehicle for inspection. Check if there are any gaps in the shock absorbers or if the suspension has any faults. If the shock absorber is leaking oil, it may be due to a faulty oil seal gasket, and the shock absorber may need to be replaced. When driving on bumpy roads, the car body may also produce abnormal noises, mainly due to the deformation and squeezing of the body caused by the rough surface. Examples include noises from the sunroof or doors. In such cases, it is necessary to clean the sunroof guide rails and lubricate them, as well as clean and lubricate the door seals. Precautions for Driving on Bumpy Roads According to normal driving habits, the typical speed on urban or rural roads is generally between 40-80 km/h. However, for obstacles like speed bumps, although there are no strict national regulations, industry standards usually specify a height of no more than 5 cm. From a design perspective, the safest speed to pass such obstacles should not exceed 20 km/h. If the speed exceeds 40 km/h, the comfort of the passengers may be affected. When the speed exceeds 60 km/h or even 80 km/h, the impact force on the car body can be several times or even more than ten times greater than at 20 km/h. Among the common speed-reducing obstacles, ranked from least to most damaging to the car body, conventional speed bumps are relatively low, cement speed bumps are the most damaging, and hard dirt mounds may fall somewhere in the middle to upper range.
When driving a small car over bumpy roads, I often hear a thumping sound. I've encountered this several times and later found out it's mostly due to issues with the suspension system. The shock absorbers or suspension springs are worn out, causing severe jolts on rough roads, which makes these parts hit the chassis, producing a dull thumping sound. Sometimes, the shock absorber oil has leaked out or the springs are deformed, unable to absorb the vibrations, causing the car body to directly bear the impact from the road surface. This is not just a noise issue but also affects driving stability, especially at high speeds where it can easily lead to loss of control. I recommend checking the suspension components periodically, such as looking for signs of oil leakage in the shock absorber tubes or checking if the springs are properly aligned. Take it to a repair shop and have them test it with professional tools. Replacing a new shock absorber only costs a few hundred dollars, which can save you from bigger troubles. Ignoring this for a long time may lead to unresponsive steering or abnormally fast tire wear. Safety first!
I usually commute in a small car, and it often makes a thumping noise on rough roads. After careful research, I found that tire pressure or wear is the key. If the tires are overinflated, they hit the rough road hard, making a drum-like thumping sound against the ground; when the wear is uneven, the edges of the potholes rub more severely, making the noise more noticeable. Once, after I replaced the old tires with new ones, the noise disappeared—the old tires were worn flat and had poor cushioning. It's also important to check if the rims are deformed or if the tire pressure is stable. Too high pressure can lead to blowouts, while too low pressure increases bumpiness. I recommend measuring the tire pressure once a month and keeping it at the manufacturer's recommended value, such as around 220 kPa for my car. If the noise on rough roads isn't fixed, it's not only annoying but may also accelerate tire wear and increase costs. By the way, maintaining a reasonable speed on rough roads can also reduce the thumping noise.
The knocking sound is mostly caused by loose chassis components, such as worn or detached tie rods or ball joints. When I was doing DIY car repairs, I found that parts rattling around on rough roads can produce knocking noises, especially when the front suspension tie rods are loose. Don't just guess based on the sound; first, try tightening key points yourself with a wrench, such as the tie rod joints under the engine compartment. If the looseness is obvious, just go to a shop and replace the parts—it's cheap, costing only a few dozen yuan. Delaying repairs may worsen damage to the chassis structure and even lead to steering failure. I once had a close call with an accident because of this, so don't let small issues turn into major repairs.
