Bought my tuck a yr ago.has 36000miles(yep,true)if I recall when I checked ,the divers front has worn bad,passanger hardly worn,(I checked about a month ago ,Im not sure on which side was worn),just took a long high speed trip and the truck pulls hard to drivers ,.my question is,what caused this?I can lock up on dirt and see all grab,there is a possibility that someone changed one side before I bought,Or culd there be a calaper or porportion valve trouble.?my intent is just putting 4 new pads on and seeing how it does,rotors seem fine,I feel no chatter like bad rotors (been there)cause