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First question: describe the vibration. Is it a constant shake that varies with speed, is it a rhythmic vibration, or is it a vibration or shake that seems to go along with the engine rpms? The rhythmic vibrations are often driveline related, but not always... they can be impossible to track down. A tire shake is usually speed sensitive only, doesn't care what gear you are in or what rpm your engine is turning. Engine related vibrations are usually rpm related, not speed related.
I imagine you've checked this, but a tire can be in balance and still be out of round. Out of round will still shake your car. Along the same lines, at the tire shop, have them look closely at the rims to be sure they aren't bent. A hourly paid tire tech could conceivably spin up the wheel/tire and bang on some weights until the machine says it's acceptable - but there can still be an issue. Also look at the treads as the tire spins to see if it wiggles side to side, often a tire fails internally and can cause weirdness.
I've had rear drums that were so poorly manufactured that the braking surface was round, but due to core shift, the heavy cast outer section was out of true and out of round. Brake rotors shouldn't be as much of an issue, but they do (or should) get balanced at the factory, and can be an issue; the vents of the rotor can become inhabited by mud daubers or simply partially filled with dirt or mud.
Shocks and springs shouldn't be the cause. If the wheel and brake is round and balanced, the shocks or springs are just along for the ride. Alignment and front suspension/ steering components usually don't cause a vibration either, only bad handling and expedited tire wear.
I imagine you've checked this, but a tire can be in balance and still be out of round. Out of round will still shake your car. Along the same lines, at the tire shop, have them look closely at the rims to be sure they aren't bent. A hourly paid tire tech could conceivably spin up the wheel/tire and bang on some weights until the machine says it's acceptable - but there can still be an issue. Also look at the treads as the tire spins to see if it wiggles side to side, often a tire fails internally and can cause weirdness.
I've had rear drums that were so poorly manufactured that the braking surface was round, but due to core shift, the heavy cast outer section was out of true and out of round. Brake rotors shouldn't be as much of an issue, but they do (or should) get balanced at the factory, and can be an issue; the vents of the rotor can become inhabited by mud daubers or simply partially filled with dirt or mud.
Shocks and springs shouldn't be the cause. If the wheel and brake is round and balanced, the shocks or springs are just along for the ride. Alignment and front suspension/ steering components usually don't cause a vibration either, only bad handling and expedited tire wear.
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