When I bought my S I "borrowed" my brother's tire guage. It was a nice analog guage and he had used it for years. It never occured to me that the guage might be giving me the wrong results.

Over the weekend I was out at my parents' house doing general car stuff. I was in the middle of checking the pressure of one of my tires that has a slow leak. My dad asked me to check his tires while I was at it. I check the pressure on his tires, and he says, "Wow, my tires are real low! That's strange becuase I just filled them last week."

So he busts out his pressure gauge and lo and behold, my tire guage is off by ~12 PSI!!

Basically ever since I have had my car I've been keeping my tires at a balloon-like 43-45 psi. No wonder I was getting a slight wear pattern straight down the middle of my tires.

Just a heads up.. you guys might want to double-check your pressure guages.

 

This should be a sticky.

 

Wow, I've found discrepancies beween 2-3 psi, but never that far! I now have 2 gauges that I really like, one a tube/stick design and the other an Accutire digital; they give identical readings so I assume both are accurate.

 

Good advice!

I had a digital POS that gave a different reading every time. I threw the piece out.

 

But how do you "calibrate" a tire pressure gauge to make sure it is giving good readings? If I try two gauges, changes are they'd give different readings, so which one do I trust? Is there some way I can test my gauge to see if it is "correct" or "off"? Thanks.

 

I have heard of being off by 10% (2 or 3 PSI) but I have never heard of being off by ten or more PSI. I work on the crew for a VW Dragster and we have a digital gauge that gets zeroed and certified after every other race weekend, if its off by even a quarter of a PSI we could bog or, get wheel hop. Those cheap-o pencil gauges have more of a tendency to be wrong, but none of the gauges are perfect. Keep an eye on your tire wear or by two gauges from different manufacturers.

 

A digital guage might be the best route.

There was obviously something wrong with my analog gauge. It's either not getting enough pressure up to the actual guage (tubing problem), or the guage is just off somehow, but either way it was giving low results.. therefore I was filling the tire to higher than it should be.

One thing I did notice after deflating my tires to the correct pressure was a dramatic increase in handling, as well as an increase in ride quality.

Edit: I have a hunch that it is probably more common that analog guages give a lower-than-normal reading, because it might be losing pressure somewhere somewhere in the system.

 

I don't actually know how they certify our gauge. I think it has something to do with the fact that air weighs 1.25 grams per litre. I'll see what I can dig up.

 

I guess most of us don't have calibration equipment.
Maybe the local tyreshop will let you check your gauge against the one they use?
Hopefully they use a calibrated one.
Or "calibrate" it with as many other gauges as you can find so you know what the fault is.
Spend $$$ on a good/calibrated one.
Tyres aren't cheap as well, and the car drives better with correct tyre pressure.

Its easy for me to say because I have a calibrated one from work.

Succes!

 

Always adjust your tires by tire wear AND the gauge... Not every tire wears the same, not every car is the same, not every driver drives the same...
There is no completely standard correct tire air pressure for each car. There is an acceptable range, just as there is an acceptable range on the tire. Although the difference on any given tire could be 20% or a as much as 30psi in what is acceptable for the application.

If you noticed a long time ago your wear was in all in the center, why did it never occur to you that your tires had too much air?

I use the tire gauge to keep my tires in range of each other, but I put air in them according to how they are wearing.