On my 02 Impala, the car starts to shake starting at around 45 mph. I went back to have the ones that already had tires on balanced, since I didn't get them done the first time. This still did not fix the problem, I did not see them balance the front ones when they put on the new tires, even though I seen them put the rims on the machine. I haven't gotten an alignment yet, but everywhere I went to said that they just need to be balanced. Thoughts or suggestions?