I recently got my car (2009 Toyota Matrix S) inspected by a reputable mechanic, and they diagnosed me with sticky calipers all around, with the back ones nearly locked. On their advice, I replaced both rear brake assemblies (pads, rotors, and calipers), and I can really feel the difference in the brake pedal operation.
They also lubed up the moving components on my front calipers, and said they should be fine for the moment. Apparently, brake assemblies on my vintage of Toyota tend to survive about 8-10 years in harsh conditions before failing, so he wasn't too surprised mine were gumming up. He runs a well-respected local Toyota-Honda shop, so I'm fairly convinced by his expertise.
However, after the work was done, I've noticed a noise/feeling from the front left brake. It feels and sounds like pad on disk noise, a very heavy scuffing, and it occurs with varying intensity with wheel rotation. It also nearly disappears during medium-hard right turns, and becomes very pronounced in medium-hard left turns.
I asked my mechanic to take a look at it, and he said it was just a very mild warping of the disk, and that I should just live with it unless I want to replace the whole assembly. But it's getting slowly worse, and only appeared after the brake job; I've taken the wheel off, and I can feel the catching once per disk rotation while spinning it with my hands. To be clear, these are the old assemblies on the front wheels that were only lubricated.
It's a very annoying noise at medium speed, and I don't love the idea of leaving brake issues unresolved for the 20k+ miles left on the front pads. However, I just paid $600 to replace my rear assemblies, and I'm not eager to pay that amount again just to get rid of what my mechanic says is just a harmless scuffing noise. So is it something I should be worried about, or is my mechanic right and I should just live with it? And in either case, is there any way to eliminate this noise without breaking the bank?