Speed-Dependent Hum/Whine and Vibrations after a Locked-Wheels Hard Brake and Skid

Question

My FWD car is exhibiting a speed-dependent (especially noticeable at highway speeds, around 90-110km/h) hum/whine, accompanied by a slight vibration noticeable at the steering wheel.

The symptoms do not change when I depress the clutch or shift to neutral. The symptoms immediately appeared after I did a hard brake of the car, that involved wheel lock (I have a faulty ABS that I need to fix) and a skid of the car on a completely dry asphalt road.

I was wondering whether these symptoms are due to tire damage (due to the skidding and/or excessive lateral forces on the side walls) or mechanical damage to the car (e.g. wheel bearing).

What differential diagnosis can I do to try and pinpoint the problem?

Answer 1

There's a lot here. I will speak generally as OP has only described a fwd car.

To start. If there is sound coming from both (two or more) wheels, that's very strange but just means you are going to do your diagnostic twice. (this will get your hands dirty)

I will call the wheel/tire assembly the 'tire' for simplicity sake.

1. Make sure the tires are properly inflated.
2. Lift the car.
3. Visually inspect the tire, there should be no obvious cracking, rotting, scrapes, exposed metal, etc. If there's something questionable, it could be the issue.
4. Run your hands over the treads, it should be even. If there is any serious tread issues, you will see it or feel it. Uneven tread wear can cause vibrations, excessive road noise, and weird steering issues.
5. Place one hand at 12 o'clock and one hand at 6 o'clock, try to rock the tire (it is a vertical motion), there should be zero play and quiet. Any play or noise is indicative of a bad bearing (indicative but not a confirmation).

6. Place on hand at 3 o'clock and one hand at 9 o'clock, try to rock the tire (it is a horizontal motion). Some steering systems have play but most do not so it depends on the car. If you have a rack-and-pinion steering system, there shouldn't be noticeable play. It should be quiet as well but any noise has to go down a diagnosis tree dependent on the steering system. (Tie-rods are a common wear item though.)

   a. If both front wheels are lifted the tire should be able to move.

   b. If only one front wheel is lifted, the tire shouldn't move much at all.

Resuming

7. If you haven't found any issues, the quickest way to rule out an interior tire issue, rotate the tire to another corner that isn't making noise. If the noise follows, you have a tire or wheel issue.

8. At this point you will need all drive wheels off of the ground and in neutral (if you are doing this on the ground make sure that you consider the parking brake and the position of the vehicle, otherwise you risk having the car fall off of its support/rack/jack stand). Spin each tire and listen for noise. Noises you are looking for are things like metal scraping, irregular noises (i.e. as the wheel spins, it makes a noise once/twice/etc per revolution), grinding, and anything else loud. The wheel should spin relatively quietly and smoothly. Metal scraping noises tend to be from the brakes, usually a warped or damaged rotor or damage to the pads.

9. At this point, if you still aren't hearing any noises, have a second person sit in the vehicle and spin the wheels and have them apply the brakes, the same rules as 8 apply.

10. After putting the vehicle back on the ground, stand at each corner and push down on the vehicle (unless you have a lowered car or one with an exceptionally stiff suspension, it will move quite easily as long as you weigh enough). Listen for noises as the suspension rebounds. It should be quiet but some squeaking isn't indicative of anything on older cars other than rotted rubber. What you are listening for is clunking, loud metallic squeaking/scraping, popping, and anything else unsettling. You're doing this last because you have ruled out anything else beforehand.

Answer 2

One common trick that techs use to diagnose wheel noise issues is to jack up the front (and rear) of the car and spin the tire be hand as fast as you reasonably can and hold onto the suspension spring. If there is a bearing issue, the spring will amplify the vibrations and make it easier to detect.

While the tire is in the air (and the car is very well supported), you can attempt to pull and wiggle the wheel to see if there is any slop in the suspension.

If there is no vibration felt, and everything is tight, then the tires are the most likely cause. Rotate the tires and see if anything changes. Even if it doesn't go away with a rotation, the sound/feeling could change which would still point to a tire issue. If two wheels locked up longer than the others, rotation could make it mostly go away.