I recently purchased a 2006 Prius with 101K miles. When I test drove the car before purchasing it, it made a very subtle hum when driving. The front tires were almost gone, so in my mind I thought replacing the front tires would solve the issue. I purchased new tires (Bridgestone Ecopia EP422) and put them in the rear (as suggested for two new tires) and placed the older ones up front. The older ones are Firestone and have a good amount of thread life left in them. Not sure of their age. So now the humming but sounds more like a grinding / binding "woo woo wooo" sound is louder and it gets louder with speed and starts from the moment it rolls. It is scary and concerning. It does not click or the sound does not go away when I make a left or right turn. At around 20 mph when the car slows down, the dash slightly vibrates. I was thinking it's the bearings, so I purchased brand new OEM Toyota hub and bearing assemblies for both front left and right and spent 6 days to replace them (What a pain!). I also replaced the rotors and brakes as well (They still look like new), thinking it would resolve the issue but the sound is still there. Everything that was removed and placed back on is torqued to spec. There are no Check Engine Lights. Front tire pressures at around 44-45 PSI. I will drop them down 10 PSI later after work to see if it makes any difference. If that doesn't do it, swap the rears and fronts. I also put it into neutral from 50mph and let it slow down to a stop and it still makes the sound. Could it be just bad tires (even though they look fresh) or worn struts or something else?
could it be the constant velocity joints? since it got worse with the back tires on the front, rotate them, putting the new ones in front, and see if it goes away. or goes back to the quieter hum as before.
When I was underneath the car, I noticed the axle was replaced in late 2013 (There was some tag with a barcode on it with the date). But yes, will swap the wheels to see what happens.
So it was the tires after all! I removed the tires and inspected the old ones that appear to look new, but noticed there was some slight uneven / bumpiness on the inside on one of the tires. I moved the old tires to the rear and new to the front and the sound moved to the back! I am glad it was nothing major. I should have started working backwards from the one variable that was changed (moving the tires around) instead of assuming it was the bearings. It's just mind boggling how uneven tire wear can sound just like worn wheel bearings, except, the sound didn't go away on turns. But it's ok, I now have less than 50 miles on my new front bearings
I actually recorded the adventure and found a trick to help get the bearing out. I will post the video once I have some time to put it together
If those tires came from the rear, just means you'll need new rear shocks now, before the new tires wear out the same way. I almost made the same mistake thinking it was my bearings making noise, as I was about to replace the bearing, I noticed the bad tire wear. Saved me a lot of time and the cost of the bearing SM-N900P ?
