If your vehicle is showing steering wheel or seats vibrate at highway speeds, here are the most likely causes and the parts you'll need to fix each one.
The most common cause of highway-speed vibration. A tire that has lost a wheel weight or is slightly out of round will cause a harmonic vibration that peaks at specific highway speeds.
Lug nuts that are unevenly torqued, loose, or missing hub-centric rings on aftermarket wheels will cause the wheel to sit slightly off-center, leading to severe vibration immediately after a tire service.
Hitting a pothole or curb can bend the rim. Even a slight bend that isn't visible to the naked eye can cause significant vibration at higher speeds.
Tires that are cupped due to bad shocks, or tires with internal steel belt separation, will cause a rhythmic vibration and often a thumping noise.
Worn tie rods, ball joints, or control arm bushings allow the wheels to shimmy back and forth slightly, which is amplified at highway speeds.
A sticking brake caliper can cause the brake pad to drag on the rotor, overheating it and causing a vibration that worsens the longer you drive, even when not braking.
Worn universal joints or an unbalanced driveshaft will cause a high-frequency vibration that is usually felt more in the seats or floorboard than the steering wheel.
A failing wheel bearing can cause a vibration, though it is usually accompanied by a humming or roaring noise that changes pitch when changing lanes or turning.
A worn inner CV joint can cause a side-to-side vibration under acceleration at highway speeds, which often goes away immediately when you let off the gas pedal.