i have drilled/slotted on three cars (96 mark viii, 2003 olds aurora and 2001 olds intrigue) and have had no problem with any of them-I did have the rotors turned on the aurora and the lincoln right after install because they 'pulsated' a friend with a machine shop thought it had someting to do with the zinc coating being uneveny applied, he said he took minimal off them to true them and the seller (on ebay) credited me the $48 I spent to have them turned. I have thousands of miles on them and like them very much, paid about $135 a set average of all three sets. just my 2 cents.