Alignment on overinflated tires a problem?

[eurosteve]

I had my Nokian WR g2's re-installed a couple of weeks ago after having the integrity's on for the warm weather. I had them installed at my local tire place and I instructed them to inflate them to 40-38. They have about 15,000 miles on them.

The next day, I took the Prius to the dealer for the 45,000 mile service. As part of that service the dealer checked the alignment and made some minor changes to the alignment.

Two days after that, noticing that the tires felt overinflated, I checked the tire pressures and I was shocked to find the pressures on all tires to be over 55 pounds! I let out the extra air and now I'm at 40 in the front and 38 in the rear.

I'm guessing that the tire place must be responsible for the overinflation. I'm puzzled about how this happened!

My question is whether the alignment has to be redone since it was done on very overinflated tires?

[dogfriend]

I don't think the difference (if any) would be significant. Theoretically, it could change the ride height slightly and they are supposed to check ride height as part of the alignment.

[tochatihu]

We are always making these pressure checks with tires cold, yes?

[richard schumacher]

As tochatihu wrote. Strictly, "cold" means "driven no more than one mile in the previous hour". High pressures after driving for hours are normal so long as the cold pressure was normal.

[fuzzy1]

We are always making these pressure checks with tires cold, yes?

Cold, and at sea level (home). And I noticed that the car was delivered from Toyota / selling dealer with 40 psi at these conditions. I did not reduce it. (OK, I actually increased it to sidewall max, 44 on my particular tire model).

When getting an oil change while traveling, I asked the mechanic to not let any air out. He answered with hostility that my tires were "dangerously overinflated", and that the shop policy was a 40 psi maximum. He refused to adjust for highway operating temperature (I had just driven 200+ miles) or elevation (6225 feet).

After returning home and letting the tires cool overnight, the fronts were UNDERinflated, 32 and 33 psi.

[eurosteve]

Thanks for the help with this. All pressures taken with tires cold. The first time, the car had been sitting for 5 hours - and the pressures were all close to 60 psi! I let out some air (down to 41-39) and then re-took the readings again the next morning after being parked all night and the pressures read 40-38.

I guess that no harm was done by this error by the tire installer. But that sure was careless!

Steve

[David Beale]

As far as the alignment goes, modern tires do not expand radially when the pressure is increased. So the alignment should not be affected by -reasonable- pressure changes. Very high pressures will make it difficult for some alignment systems to be used. They force "fingers" under the tire bead to hold on the mirror assembly. So it's harder to install it with very high pressure. But I'm sure the alignment guy will get it on!

[dogfriend]

Originally Posted by David Beale

As far as the alignment goes, modern tires do not expand radially when the pressure is increased. So the alignment should not be affected by -reasonable- pressure changes. Very high pressures will make it difficult for some alignment systems to be used. They force "fingers" under the tire bead to hold on the mirror assembly. So it's harder to install it with very high pressure. But I'm sure the alignment guy will get it on!

Yes, I agree, and if you watch how the alignment is performed, you can see that the reference plane used to locate the mirror assembly is actually the outer surface of the rim just inside the tire bead. The profile of the tire doesn't enter into establishing the reference plane for each wheel.