I put brand new OEM calipers from the dealer two years ago. A month ago, I opened the bleeder screws, pushed the pistons back in fully to purge the fluid in the calipers from the bleeder screws. Then I flushed the front lines while topping up the master cylinder. It's but one way to get more life from a set of calipers.

Good tip. Probably unwarranted but I just didn't trust them after they seized up.

Likely Culprits (in order of probability):
* Warped Brake Rotors: This is the most common cause of steering wheel shake when braking, especially at higher speeds.
* Why it fits: Downhill braking generates more heat, which can warp rotors over time. The shaking at low speeds on uneven surfaces might indicate uneven rotor wear or deposits.
* What to check: Visually inspect the rotors for any signs of warping (uneven surface, blueish discoloration). Measure rotor thickness and runout (wobble) with a dial indicator.
* Sticking Brake Caliper: A caliper that doesn't release fully can cause uneven braking and shaking.
* Why it fits: Might explain the low-speed shake if the caliper is dragging slightly.
* What to check: After driving, carefully feel the temperature of each wheel hub. A significantly hotter one suggests a sticking caliper.
* Suspension Components: While you've upgraded some parts, worn bushings or ball joints can introduce play and contribute to shaking.
* Why it fits: Loose components can amplify vibrations, especially on uneven surfaces.
* What to check: Have a mechanic inspect for any excessive movement in control arm bushings, ball joints, and tie rod ends.
* Wheel Bearings: A worn wheel bearing can cause vibration and shaking, sometimes more noticeable during braking.
* Why it fits: Less likely given no vibration at speed without braking, but still worth considering at 250K miles.
* What to check: Jack up the front end and check for play in the wheels by grabbing them at 12 and 6 o'clock and trying to rock them. Also, listen for any grinding or rumbling noise when spinning the wheels.
Less Likely (but still possible):
* Tires: While you've rotated and balanced them, there's a slight chance of a tire issue, especially given the low-speed shake. Check for uneven wear or any bulges/damage.
* Steering Rack: Problems here usually cause more consistent issues, but wear can contribute to shaking in some cases.
Where to Start:
* Thorough Brake Inspection: Start with the most likely cause – the brakes. Have the rotors inspected and measured. If they're warped or excessively worn, have them resurfaced or replaced (along with new pads).
* Caliper Check: While inspecting the brakes, check the calipers for proper movement and signs of sticking.
Important Notes:
* Don't automatically assume warped rotors! While common, it's crucial to rule out other issues.