As usual, resorting to the brilliant shared knowledge here for some help hopefully on a topic I'm absolutely lost on.
Since the day I bought it, my 2005 Legacy GT has had a wobble when braking that seemingly comes and goes for no known reason. Previous owner installed a big brake kit (sigh, brand unknown) - with large slotted rotors, and calipers much larger than stock. I love the performance and the feel...when they work right. Potatocam picture of my car from when I bought it, you can somewhat see the large rotors and calipers on here too:
Here's what happens - when I brake softly I feel a horrible wobble through both the wheel and the pedal. Definitely from the front wheels - my senses tell me it's the left wheel. Kicker is, the car will go months without ever feeling this, and then suddenly it returns - currently it's back and happens everyday - but only on soft braking. If I brake with a good amount of force it's smooth and not wobbly at all.
I've had my mechanic look at my pads and rotors - both of which he says look fine, no warping on the rotors. I had some pretty bad wheel bearing noise developing, I thought the worn out bearings might be causing this - replaced the hub assembly recently, but still no fix to the wobble. I've rotated the wheels and had multiple sets of tires mounted and aligned, still same issue.
Any ideas? Would it be worthwhile to disassemble the calipers and clean them out, to make sure they're working properly (would a mechanic even be able to fix this though, if it's not?). I know it's less than ideal, but my mechanic said he could try resurfacing the rotors to see if that would fix it as a last resort. Worthwhile?
Taking out the brake kit and replacing it with OEM parts would cost over a grand, and would result in significantly lesser braking performance - so I'd like to try salvaging my current setup if I can.
What would you do to try fixing this, OPPO? Anything you would do that I've missed at this point?