I have a 2007 3I that has about 53K miles on it. I had replaced all 4 tires back in Oct. of '09 and I had an alignment done at the same time. Since January of this year I have been noticing a "thumping" noise coming from the passenger front tire that I thought was a wheel/tire balance problem. Took it in to the Firestone shop and they checked out the car and tires. They say that I have a bad wheel bearing.

Don't know if I trust them because there is no grinding-type noise and the car tracks just fine. They quoted a price of $575 to do the job. My questions are;

do you always replace the bearings in a pair or can one be replaced alone?

is it easier and more reliable to replace the entire wheel hub assembly instead of just the bearing (do the hubs come off easily with no need to press out/in the bearings)?

how can I be sure that it's a wheel bearing and not the wheel/tire that's the problem?

 

I'd get a second opinion of what is making noise, 53k is early for bearing failure. Ask mazda if it's covered in the powertrain warranty, since it's a drive axle and you're within 60k 60 months.

You're right that should be more of a grinding noise. Does it thump once per tire rotation, or more often?

Some tires take a set and end up with a flat spot after sitting, so verify your tire pressure, and maybe rotate tires to verify it's not the rim or something else.

If it is the bearing, no need to do them as a pair, but have the other side checked for problems. Shouldn't be much benefit replacing the hub assembly vs the bearing only, but i think it is a press together for the bearing seat, and not something i'd suggest doing yourself.

Have someone check your CV boots, if they are cracked at all this is when to change it.