Hi guys,

As some of you know I have a 2007 Mercury Grand Marquis LS. I just took a 600 mile roadtrip and noticed that between 55 and 70 mph, it STILL has a lot of shake going on.

Backstory: I bought the car in February with 74,500 miles. It had BF Goodrich tires on it that looked very old, but had decent tread. I live in Pensacola away from my parents, and when the car's A/C computer failed, we decided to swap cars and they would get it fixed while I was working and at college. Then, we would trade back the next time I was at home.

Well, the shop that replaced my A/C pointed out to my Dad that the tires were dry rotting, and suggested they be replaced because they could have failed him on the highway. I should mention that with the Bf Goodrichs, there was no shake or vibration at any speed. As a result, without telling me, my Dad had the guy put on a set of Fuzion ZRi's (same size, 225/60R16) and had them balanced. My Dad had the car for a month. The day I took the car out I noticed the shake. So I had it re-balanced. Still shakes.

Took it back to Pensacola, had it re-balanced again. Guy and this shop says the balance was way out. Not as bad, but still there.

So, other than balance, what can cause this? Alignment? Damaged wheels?