You hear humming, knocking, or something rattling while driving, but when you pop the hood the engine runs quietly? Sounds coming from underneath the car, from the wheels, or from the rear confuse even experienced drivers because they change depending on speed, road quality, and steering direction. If you're interested in noises from the engine bay itself, we covered that in a separate guide. Here we deal with everything that hums, knocks, and squeals outside the engine, and it's precisely the location and circumstances under which the sound appears that tell you more than the character of the noise itself.
Humming that increases with speed, wheel bearing or tyres
A constant hum that gets louder the faster you go most commonly comes from a wheel bearing or problematic tyres. The key difference is in the behaviour during turns. If the humming disappears or decreases when you turn one way and gets louder when you turn the other, it's almost certainly a bearing. The reason is simple: during a turn the load shifts to one wheel, and the damaged bearing reacts louder when it carries more weight.
You can do a simple test yourself: drive at 50-60 km/h on a straight road and gently move the steering wheel left, then right. Notice when the sound changes. The side where the sound increases during a turn usually has the faulty bearing (the opposite wheel from the direction you're turning). A wheel bearing typically lasts 80,000-150,000 km depending on driving conditions and road quality, but on the roads in BiH that lifespan can be shorter. Ignoring the humming leads to a complete bearing seizure, which is a dangerous situation while driving.
Tyres with uneven wear or poor balancing produce a rhythmic droning that doesn't react to steering but changes with speed. Visually inspect the tread pattern, especially the inner edge you can't see without bending down. Uneven wear often points to a missed balance, bad alignment, or already worn-out shock absorbers. If one tyre shows pronounced wear on one side, just replacing the tyre won't solve the problem because the new tyre will wear unevenly again until the root cause is addressed.
Knocking and rattling over bumps, suspension components
If the sound only appears when you go over a pothole, a curb, or damaged asphalt, the cause is most likely in the suspension system. The usual culprits are stabiliser links, control arm bushings, and shock absorbers. Stabiliser links are typically the first part to give way, recognisable by a metallic rattle over smaller bumps. On most cars these are inexpensive parts, but when neglected, a loose link accelerates wear on other suspension components.
The difference between a link and a shock absorber: a link rattles briefly and sharply, while a worn shock produces a dull thud and the car continues to bounce after the bump. Bushings make a squeaky noise, especially during hard braking or pulling away. On older cars, bushings crack from rubber ageing alone, not just mileage.
We covered a more detailed diagnosis of knocking over bumps in a separate guide on knocking sounds, so we won't repeat it here. The important thing to know is that this type of noise depends on the road surface, not on speed, and that's the key diagnostic sign that separates it from a bearing or tyre issue.
Clicking when turning, CV joint
A rhythmic clicking that only appears when turning with throttle applied, especially when pulling out of a parking spot or at full steering lock, almost always comes from a worn CV (constant velocity) joint. This is characteristic of front-wheel drive, and the sound gets louder in a sharp curve under load. The sharper the turn and the more throttle you give, the louder and more frequent the clicking becomes.
You can do a first check visually. Look at the rubber boots on the driveshafts near the wheel. If a boot is torn or greasy from leaked grease, the joint has been running without lubrication and wear has already progressed. The sooner you react, the better the chance of just replacing the boot and repacking grease instead of the entire driveshaft. A boot can be torn for weeks or months before the clicking becomes audible, so it pays to occasionally look under the car, especially after winter when salt and moisture speed up rubber deterioration.
Droning or rumbling from underneath, exhaust and propshaft
A deep droning or rumble coming from underneath, especially at higher speeds, can be an exhaust pipe touching the underbody or a worn propshaft bearing (on rear-wheel drive or 4x4 vehicles). An exhaust that vibrates typically produces a metallic resonance at a specific speed, while a propshaft bearing creates a constant hum that increases with speed. With a propshaft bearing, the droning sometimes increases during acceleration and decreases when you lift off the throttle and the car coasts in neutral.
Corroded or broken exhaust hangers (rubber mounts) allow the pipes to shift and hit the underbody. This is easy to check visually from underneath. If you see a pipe sitting close to the body or a rubber hanger missing, that's likely the source of the sound. Replacing a rubber hanger is a minor job, but if the sound is ignored, the pipe can wear through the body's protective coating and create a corrosion spot.
Squealing when braking, corrosion or worn pads
Squealing during the first braking in the morning or after rain is usually surface corrosion on the disc. This is normal and goes away after 2-3 brake applications. However, if the squealing or scraping persists constantly, especially if you feel vibrations in the pedal or steering wheel, it's most likely worn brake pads or warped discs.
Most modern pads have a wear indicator, a small metal tab that starts scraping against the disc when the pad material is nearly gone. That sound is intentionally unpleasant to make you react. If you hear it, don't delay an inspection because driving on worn pads damages the discs, and replacing discs costs several times more than pads alone.
How to narrow down the source before visiting the workshop
The most useful trick you can try yourself: drive slowly (30-40 km/h) alongside a wall, fence, or parked cars with the window down. The sound will reflect off the surface and you'll find it easier to determine which side it's coming from. This also helps the mechanic because you can tell them the specific side and circumstances.
Pay attention to three things: does the noise depend on speed (bearing, tyres, propshaft), on road surface (suspension), or on steering position (CV joint, bearing). That information drastically narrows the list of possible causes. Also note when the sound first appeared, whether it was gradual or sudden, and whether it changes when the car is cold versus warmed up. All of this helps the mechanic reach a solution faster.
If you're not sure, stop by the workshop. We diagnose noise using a combination of a lift and a test drive because some sounds only appear under load, and that can't be simulated while stationary.