Pontiac sunfire problems. Big surprise!
 

My girlfriend has a 99' pontiac sunfire. I know it's a notoriously unreliable car! lol. Recently she took her car in for a grinding and thumping noise coming from the front of the car. The dealer replaced front brake rotors and pads which solved the thumping. They said the grinding sound was the probably tires. I also asked them to check CV joints and wheel bearings and they said both were fine.

I was thinking the grinding sound (you can feel a little bit of vibration too) was the tires. It gets louder with increasing speed and levels of at about 50MPH. The thing that is throwing me off is the noise is unaffected by hard conrnering or turning. Which noise from bad wheel bearings or bad tires would at least change a bit when cornering.

Any suggestions?

If you have problem with GM cars, your best bet is to check their TSBs. There're like a billion of them out there, almost all have them have similar problems (wonder why? ;)). You can usually find the source of the problem with a simple search. I found out about a loose connection problem on mine couple of months ago, that saved myself a pricy tranny job.

http://www.alldata.com/TSB/48/994826F7.html
http://www.alldata.com/TSB/48/994826GK.html

Not sure if the tires are really the problem, it's possible though. I know for some N body cars, there was a problem with the goodyear eagle LS/RS-A. Basically they had to replace the tires with a newer revision in order to get rid of the noise. Don't have the TSB handy but you should be able to find it easily.

if you have cold, snowy weather, than that can sometimes cause the front suspension to freez up cheap parts like bushings. snow and ice build-up around the wheel area may also be a cause of this.......other than that, if you have the opposite climate, then i suggest you take it in for a check up immediatley