I just had my winter tires mounted on my stock 17's yesterday, then had a four-wheel alignment completed.

I know that a difference in PSI from tire to tire will toss off the alignment and cause the vehicle to pull in one direction or another.

But, what effect does PSI have on the actual physical alignment of the wheels?

I measured the PSI's this morning, and i found a 3psi difference from highest to lowest, and this is how the vehicle was alligned.

If the PSI if "off" when the vehicle is on the machine, and the technican makes adjustments, are those readings / adjustments compensating for a difference in PSI?

Or, regardles of PSI, the physical allignmets as measured on the machine will stay the same and while the alignment machine will say "perfect", the vehicle will pull to one side or another until the PSI is properly set, and changing the PSI will not toss of the measurements???

Should I go back and have the vehicle re-measured?

I know the question will come up. Im using a calibrated / cartified guage accurate to the 0.1 psi

 

To my mind, a small variance in tire pressures doesn't throw off the wheel alignment. Only changes in suspension geometry will do that (after hitting a curb for example, or changing out parts due to repairs).
I'm sure that if you asked the shop that aligned your ride, they'd say that pressures have little or no affect on alignment.

C.

 

3lbs won't affect alignment. 10-15lbs will because that will change the angles. Most garages will tell you that alignment is a science and is only a general adjustment to point you in the right direction squarely. The first bump you hit can alter the alignment.

 

When alignment is done one of the first things to do is make sure all tires
has the same pressure. Since you checked the pressure this am you
got cold tire pressure which is often several lbs diffrent from warmer day
pressure. Anyway it won't have any effect on your alignment....not that
critical. Also your tire gauge may be off by three lbs.....most are!