Putting larger, and most likely heavier wheels on your car will move the weight out farther and have a negative effect on the acceleration and breaking of your car.. It sounds like you are now feeling the uneven surface between the disk and pads. Your disk may well need to be cleaned by polishing to remove pad materal deposits.
I have the same shudering problem on mine. I went from 15 to 17, had the wheels balanced, front end alignment and the front rotors turned and still have a shudder when i hit the brakes. I only feel it when my speed is above 30 mph and i am coming to a stop. I have been to the dealer 3 times on this, and the in the end I am just going to have to upgrade the front brakes and you maight have to do the same. Now if anyone out there has a old brake system from a cougar that had 16's on it, I would be willing to buy your old rotors off of ya.
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