Vibration at highway speed

Where do you feel the vibration? Is it the steering wheel, the seat of your pants, the floorboards, maybe one of the pedals?

Hi guys. Suspect a bent wheel. Remove the tire, install it on a spin balancer, then use a dial indicator to measure in four places; up and down, then left and right, on the inside of the wheel's lip on the outer bead area, then those two places on the inner bead area. Typically the maximum allowable is.045" at any one place, but you will feel even less than that.

Have the tires balanced with a road-force balancer. That takes a slightly bent wheel into account and looks for the best way to install the tire to minimize that "runout".

Look at the hubs for corrosion that is stuck around the center hole, especially if you have cast wheels. Chunks can break off and turn to powder that sticks around the studs and prevents the wheel from sitting squarely.

Install a wheel without the tire, then use the dial indicator to measure runout on the car. That will make a bent wheel, impacted corrosion, bent hub, etc. Show up, but then you have to figure out which of those is the cause.

Remove the brake drums and rotors and check for rust buildup behind them. Front-wheel-drive cars have access holes in the hubs to stick a socket through to remove the wheel bearings. Water can splash up there and form rust on the rotors and drums in those holes. Every professional knows to sand or scrape those rust spots off before machining a drum or rotor, otherwise if they aren't reinstalled in the same orientation, they will prevent them from sitting squarely. You can measure the resulting runout with the dial indicator, and any runout will be multiplied by the diameter of the tire. Almost all do-it-yourselfers overlook this important step during a brake job.

Failure to remove those spots of rust can result in the part not sitting squarely on the brake lathe. A warp will be machined into the drum or rotor. That type of warpage on a drum usually causes a vibration only during braking, unless the rust is still wedged in there. Warped rotors will cause the caliper to slide back and forth twice per wheel revolution. The faster you go, the more force it takes to do move that caliper, and the more likely you are to feel it.

They aren't always this involved, but you've already done more to find this than most people do. Most of what I listed is addressed during other routine services, ... But you have to know about these things first.