When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have a 2012 Explorer Limited with 95K miles. Under medium to hard braking, the steering wheel wobbles, and the car slows irregularly. I'm struggling to find the best word to describe. It's not a vibration or a shudder. It's like a pulsing that is slow enough to be counted. The car doesn't pull to a side under braking, either.
I put a dial indicator on both rotors, and they are nearly perfectly flat. There is no evidence of a leak anywhere. The only think I noticed is that the DS caliper had a little more pressure on the rotor, making the rotor harder to turn than the PS rotor.
A brake pedal pulsation under braking is almost certainly due to a rotor that is either warped or not running true. It doesn't take must to cause it either, just a few thousandths of an inch can cause a noticeable pedal pulsation. And if you're absolutely certain that there is no measurable runout on the inner or outer brake rotor surfaces, then you may either have a surface contamination or something stuck between the rotor hat and the hub that is causing the rotor or rotors to not run true. If the wheels were loosened just prior to this happening, rust may have fallen from the rotor vents to the hub.
After merely taking the front wheels off and measuring the rotors, the pulsing has reduced about 80% (at least for now). There is still some still some steering wheel wobble, but the pulsing is barely felt until the car almost gets to a complete stop.
With that information I'd be very suspicious of rust or other debris that was sandwiched between the rotor had and the hub. When you removed the wheel the debris would have had an opportunity to drop out with gravity's help.