I own a 2005 dodge neon sxt. I have had a rear hopping at 50 or so mph issue for a couple months or so, I know i had one bad rim as so i was told so today 10-15-09 i had new wheels installed and yet again i have a hopping issue, I have new tires on well they were new back in march, i asked no issue with tire no wearing problems or anything but then i feel the hopping around 50mph. I called back it was balanced correctly so now i'm out of idea's. The car's suspension is stock car has like 78,900 on it. any idea's..

 

Is this an up and down hop or more of a side to side? You said this has been happening for a couple of months so I am assuming this was after you put the new tires on. Try swapping the front and rear tires to eliminate the possibility of a bad tire I have seen the odd new tire with a manufacturing issue like a lump or hard spot. The bad rim you had, was it damaged on the car and if so did you check for strut or suspension damage on that side? If you swap the front and rear tires and the hop does not change I would suspect a weak, bent or otherwise bad strut or alignment issues.