Disclaimer-I’m not a trained technician, just a drive-way DIY “mechanic”. You’ll have to evaluate the support or flak I receive from this opinion.
“No, I didn’t lubricate anything. I just removed the 1 bolt, swung the caliper up, and swapped out the pads.”
It could be that one of the calipers/pads were seizing in their mounts (not the piston) because of corrosion before you did the brake pad replacement and that caused the vibration (explained later). Since you didn’t clean and lube anything then problem continued after the replacement.
“On the left side the inner pad was worn much thinner than the outer. And it was uneven, with the greater wear in front.”
The smoking gun? To me this is the smoking gun that indicates that my theory is correct. I seldom replace pads only, without rotors and this is one more reason. When replacing rotors on my vehicles the calipers must be remove (except hydraulic hose). At that point I thoroughly clean all mounting surfaces for calipers and pads, any pins etcetera, and lube everything carefully (Messy, I use wire brushes, files, drill w/brush, etcetera.) I grab the caliper after installation and make sure it is free to move.
My Theory-Here’s what happens…
When the brakes are applied to stop the piston presses the inboard pad against the rotor. That causes the caliper to “pull” the outer pad against the rotor and both apply fairly equal pad pressure to both sides of the rotor. Also, there is a little wiggle room to compensate for small amounts of rotor run-out because the caliper and pads can wiggle with the rotor.
When the caliper and or pads can’t move laterally then the caliper piston presses the pad against the rotor, but the outer pad does not get pulled against the rotor with as much force if the caliper and/or pads can’t move inward. This wears the inner pad faster. Also, the wiggle room is eliminates and any run-out existing in the rotor is transferred to the caliper carrier and car. That’s why the car shudders, rather than the steering wheel alone. More pedal pressure is required and still does not deliver full braking power!
Let me guess, You live where road salt is used during the winter months. I do and that’s why I know about this. Been there, done that.
Solution? Why not just replace pads and rotors, clean and lube attaching parts thoroughly and make sure everything moves.