The rear tires of my 04 S are cupped on the inside like I've never seen before. I have no idea what caused this problem to this extreme?

 

How often have you rotated the tires? My tire guy pointed out the same thing on my Subaru wagon. With a FWD car, there is just not enough weight in the back to make the tires behave, he said, and suggested I rotate tires more frequently.

 

this is usually due to one of the following:

1) worn shocks
2) improper alignment (yet wouldn't happen on rear tires)
3) lack of rotating tires

...I'd rotate your tires and they should begin to wear evenilly, (i.e. the cupping will wear wear away in the higher points so that the tire corrects itself over time). -just be sure to rotate em every 5k or so.

 

I would check the toe-in on the rear tires.

 

 

Possible causes....either singally or combined

Rear alignment settings
Improper air pressure (check load/inflation tables)
Worn/malfunction shock absorber
Worn bearing(s)

 

I would bet on the rear alignment being out and since an 04 has no adjustments on the stock control arms you will need a set of lower rear adjustable control arms. PM for more info about ours. Cheaper then buying new tires every 10K.

 

yeah i just rotated them and reset the pressure at 42 pounds.
made it go away.

 

42lbs???????

 

Holy crap. I'm hoping that's not cold. 42 PSI cold is well over 50 PSI hot. That's over a lot of tires max inflation pressures.

I run 31 front and 33 rear COLD pressures on my car for the street. My track pressures are all over the place depending on how the car is feeling.

 

yeah guys cold.
thats due to my engineer dad. hes the one who sets it there. hes nuts every time i check them they are 42 pounds. i take them down all the time then he pushes them back up. i have noticed the car pushes alot.....

 

Eek... The tires are going to be way overinflated at 42 psi cold. Glue the tire caps on so your dad doesn't overfill them...



Below about 27 psi cold your tires look like the first picture. from about 29-35 they'll look like the middle pic. Much past 37 and they'll start to look like the picture on the right.

Yea, it decreases rolling resistance (Nice for gas milage) but it also means you have no tread in contact with the road.

 

Sounds like Dad needs to buy the next set of tires They are cupping due to the very High PSI.

 

I would look at the rear shock. i have seen several cars come in here with a really bad rear rear tire and ti is due to some type of bad rear suspension part, a shock, a wheel bearing, bad alignment, things like that.

also 42 psi cold is WAY to much. check his gauge, it may be bad also.