I have 3 pencil air gauges and one dial analog gauge. They range from 3lbs low to 8 lbs high across the 4, when checking one tire.

How can we know if a gauge is reading right? Where is the tester for the gauge?

Good question. This has been one of my issues for years. Search Google to see if there's a "standard" or calibrated air pressure guage that's commercially available. Please let us know what you find.

I guess with any measurement equipment you purchase, there is always the question of measurement accuracy. For example, how accurate would a $3 tire gauge be? How about a $30 tire gauge? Not sure how one would go about calibrating a tire gauge.

If you believe in random population distributions, I guess you could buy like 10 $3 gauges and take the average of all ten...

With N = 10 or even 100, the average can still be off (poor accuracy).

In my experience, it doesn't really matter. Pick one gauge and go with it.

You are really only interested in the differences across your 4 tires.


If the gauge is off by a few pounds, it will be off the same for all 4 of your tires, which is not a problem at all as long as you always use the same gauge.
Andy

I agree with Andy about differential between tires, with one caveat -- get a decent quality dial gauge (no less than $30) with an air-bleed valve. That will make it much easier to lower the pressures if you bump them up too high when refilling every time you gas up for daily drivers, or when bleeding off air between autocross runs.

I purchased a dial analog tire gauge from the "Snap-On" tool guy a few years ago. Coincedentally, it measures exactlly the same as the shop gauges that were hooked up at the Honda dealer that I worked at then.

Recently, I had my gauge checked against those in use at the Audi dealership where I now work, and once again, the readings were the same.

I use that gauge for the cars, motorcycle and bicyles. The "pencil" gauges did not ever seem to be consistant with their readings, even on the same day with the same tire My analog tire gauge was only $18, a most worthwhile expenditure. I'd recommend buying a decent gauge and comparing it to a trustworthy shops' gauge, someone you might have some rappor with.

At bigger races, both auto or motorcycles. There is almost always a big tire supplier. They have a test station where you are free to check your gauges.
Every other time I go to an event I take my gauges and test em for accuracy.
Its got a big dial gauge or digital read out that shows the pressure and a shrader valve for you to test your gauge.

I would agree having all your tires the same is a key. However I think having the right pressure is just as important. Not to sure about cars, But if I was racing my roadracing motorcycle with the pressure off 4 lbs.... I would not be getting the tires to the right temp or getting em too hot.

That's why we take tire temps at the track. Way too many factors that play into this, pressure is just one of them.

One pressure won't work at every track on every day. Heck, even the time of the day can influence what pressure to run.
Is it sunny or shady? Rain? Morning, noon, evening?

Tire temp will tell you where your pressure needs to be for that day and time and track.

There is no one correct tire pressure for your car.
Andy

PS: However, none of that is really important for a street car on street tires. You'll be hard-pressed to find someone who can tell the difference between 30lbs and 34lbs on a street 914 with street tires ...

When I couldn't get a consistent reading, I stopped at my Discount tire store and had them check the pressure. I was running 26/28 lbs from home. They let air out of all my tires telling me I was in the low 30's on all.

My quest is to take all my gauges to the TMS Nascar in a month and find the tire booth. Good info.

Uh, how far did you drive to the tire store, and what was the ambient temp? Tire pressures in the low 30s' sound good to me. Your tires could have warmed up to those numbers by the time you got to the tire store.

About 3 miles at 40mph. I didn't think it would heat up that fast. I always check cold at home before going out.