"Are you serious? Hitting a puddle of water can warp the rotor."

You bet it is. I had brand new rotors warp on me with less than 1000 miles. I complained to MB about it and, after some discussions, they replaced them. The MB rotors are not ventilated (300E) and are prone to heating/warping. They are inexpensive but...

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Reno

'93 300E 4Matic
'98 Nissan Altima
'00 Yamaha Road Star Silverado