highway smoothness

[Esper]

hey, i have a problem. whenever i get on the highway and get up to about 70mph, i get this rapid bumping feeling through the car (i can mostly feel it through the gas pedal). it smooths out a little by 80mph, but comes up again by 85+. it doesn't happen if i go slower than about 68mph. Its not a big deal, you can't really feel it if you're not driving, but its bugging me. The car drives strait if i let go of the wheel, and the tire pressures are right. i can't see anything wrong. Do i need an alignment? it seemed to start after i replaced the brake pads in the front, but i don't know for sure. i know they were installed correctly, but could i have messed up something as i took the wheels off and put them back on? i'd appreciate any help. thanks.

[93mxrgs]

get ur wheels balenced, you prolly threw a weight sumwhere