Sounds like uneven pad deposits on the rotors. Try bedding the pads in correctly per the pad manufacturer's guidance. Also verify your lugs are torqued correctly.
I dont think driving in the rain can cause rotor warping, especially since the rotor would be spinning, and cooling across the whole rotor evenly, aka no un-even cooling.Wrapped rotors. It has to do with the thermal expansion and retraction of the metals in the rotor as they are used. With the fall and winter coming upon us it usually brings rain which once splashed on hot rotors under breaking will cause them to cool down as a rapid pace, thus causing the warping of the rotors. Get them turned if they are within spec (need at least .0030 of an inch above the minimal number cast into the rotors) otherwise get new rotors.
...and pulsating like this is usually caused by a warped rotor. What happens is, you hit the brakes, the ABS gets thrown off due to the warped rotor, then the pistons in the calipers have a hard time retracting quick enough. The warp basically jams the pistons back in very quickly, the pistons get jammed and this eventually will create gouges/rings/imperfections in the caliper shaft where the pistons live. Once this happens, your calipers are toast. I strongly recommend you take the calipers off, pull the pistons out (ALL of them), and inspect. If the caliper shafts are still smooth (and the pistons have no sign of damage..all it takes is a tiny nick or something), get a piston seal rebuild kit and put back together. If you simply replace the warped rotors without inspecting the caliper shafts you will end up with more warped rotors once again because the pistons will still be binding again, and as a result, will cook the rotors and warp them. Trust me on this one, I've been through it on a couple different cars. Most people simply replace a warped rotor and fail to inspect the caliper shaft for damage. Its an endless loop unless you address EVERYTHING properly.Sounds like a brake pulsation to me. If the brake rotors have been overheated they're likely warped which will cause the issue you are describing.
Guys let's not start a flame war over thermodynamics. I'm sure we can all agree that when it rains, puddles can, and will, form. And we can all agree that a puddle has a much larger capacity to cool down a brake rotor than a couple pf rain drops. It's therefore pretty likely that if you hit a puddle at the bottom of a hill or after a couple of hard braking events your hot brake rotors is going to get doused. Now unless the water from this puddle manages to hit all surfaces of the rotor, inside and out, then the rotor is going to cool unevenly. Furthermore, the center of the brake rotor is mated to the hub on the inside and the wheel flange on the outside which means that in all likelihood the center of the hub is going to stay warm longer than the exposed braking surface. This explains why many more customers come in during rainy season complaining of brake pulsations.Sticking to your guns I see. I'm not doubting the complaints, I'm telling you the physics of heat transfer. The amount of energy that rain drops can absorb from a hot cast iron brake rotor is negligible (unless your driving through standing water...). It's a concept known as thermal mass or thermal inertia. Put it to you this way, if a go kart and a Semi get in a head on collision, how much is the Semi going to slow down?
And like I said, even if your rain water cooling could suddenly cool off the rotor as you suggested, the rotor is spinning and would cool evenly, thus no warping.
If you need a book to tell you how something works that's your thing.If you need, I can break out my heat transfer book and show you the math...
Guys, I said rain drops, because that's what rain is. Water on the ground is puddles. Water splashed up is also in the form of drops.If you need a book to tell you how something works that's your thing.
I'm making the statement from experience, not a theory. Having done more brake jobs in one day than the average person will in a lifetime and more in a week than the average car guy will in his life. I think my first hand experience has more than just quoting a book behind it to stand on.
And it looks like you're sticking to the whole thing that I said "rain drop" which once again I never said. So until you are able to accurately challenge my experience, your challange that rain/rain water/water has nothing to do with warping rotors is moot.
It however seems that the person posting below you grasps what I said.