Tire Pressure Guage

[Por_sha911]

I have always checked my tire pressures on a regular basis. I have an old but very expensive pressure gauge that I've used for years and its always been consistently dead on. I recently found out that it has gone way off (about 5-7 lbs). Sooo, this begs to ask a few questions:
1) What gauge do you use? Is digital any better or worse?
2) How do you know its accurate? Who's to say that the one at the tire shop is any better or worse?

[bmgmd]

Used to use the mechanical ones up to a few years ago. Then I read in a car magazine (R&T or C&D?) a few years ago when they tested the digital ones. The digital one was much more accurate and consistent; since then, it's been digital all the way.

Problem is that now there are cheap ones and I can't remember what brand was tested/recommended. It might have been "Accutire"? I think it was the same as what Tirerack was giving away with purchase of 4 new tires a few years back.

Hope it helps.

Brian

[KFC911]

I've had one of the Accutire digitals (the larger one that comes in a case...approx. $20-25) for a few years and really like it. I got mine from Tirerack, but I've also seen them at Sears, etc.

[Vipergrün]

I have a Longacre mechanical I like a lot. Accurate, easy to bleed of air, no batteries to die, etc....

[Paulporsche]

Digital. Accurate (?) to .5 lb.

[Nine9six]

The digitals are all over Ebay for less than $15 shipped

[M725ROB]

Are you sure accuracy is important to YOU? Consistancy beats accuracy in my book. If you've figured out what pressures your car needs and your current gauge says the same thing every time, keep it! If you get a new one you'll have to go through all the experimenting again. I've got a Milton pencil style gauge (about $7) in each of my cars.
Rob

[KFC911]

If a guage is always accurate, it goes without saying that it is consistent. It's nice to have the former, but I hear where you're saying.

[charleskieffner]

the way it was explained to me by anglo-american racing phx is.................if your tire pressure is say 29 and 36 psi. buy gauge incremental like 20 psi to 50 psi. if say 60 psi get one that reads 40-80 psi this is for true dead nuts as you can get race car/truck/buggy race tire pressures. you get what you pay for. i was looking at digitals with +-.5 psi but i think they have steered me towards dead on longacre type when i get the bucks. this kinda reads true due to quad tires having low psi and standard gauges not really reading accurate for low pressures like 8 psi and such. special quad low pressure gauge is needed for accuracy. buying one to go from 0-100 psi as a do it all gauge, your accuracy suffers greatly.

[Early_S_Man]

I am amazed there are many people who assume that the number of displayed digits on any kind of digital meter or display ... implies additional accuracy that is simply not there in the specifications!!!

A typical case is the $9 digital multimeter or tire pressure gauge ... many of which have no actual specifications in the owners manual, but rather just a listing of the range scales and display maximums!

I defy anyone to explain the usefulness of the rightmost digit on a 3-1/2 digit display when the stated accuracy is +/- 2% to +/- 5%. Even if accuracy is stated as +/- 2% of full range ... 2% of 199.9 psi is ~4 psi, so what is the value of the tenths' digit so many people are impressed by???

[randywebb]

Warren - I'm not amazed at all... very few people take any science courses anymore and hence never learn this...


BTW - I recall that test - the AccuTire really was more usefully accurate.

[Early_S_Man]

Randy,

I have seen several tests in magazines over the years where the Accutire gauges were rated #1, however, none of those tests that I recall ever tested a Draeger gauge, my personal favorite. There is essentially no difference in the readings that I get between a couple of the Draegers, a couple of Accutires, and a couple of late digital gauges I have, and all are consistent, reading within 1 psi.

As far as reliability goes, as long as a mechanical Bourdon tube gauge isn't subjected to high-shocks to the point that pivots or jeweled bearings are damaged ... Hooke's Law assures consistent readings, just as on a beam-type torque wrench! The Accutire and Draeger gauges I own are over 30 years old and though no longer looking new ... they still perform that way.

I never trust any work done at a tire shop ... it doesn't seem worth risking your life on work done by distractible kids being paid [not really earning, just being paid ] minimum wage! That means both lug nut torque and tire pressures get checked immediately after leaving the tire store! I have personally seen 15 out of 20 lug nuts [in one set] that were only finger tight, and tire pressures from 18 psi to 69 psi on a car that should have had all at 35 psi!

[randywebb]

No argument - however, many use the spring type, pencil gauges. Then there are the cheap ones that just look like the Draegers.

IIRC, some of the pencil gauges were off by several psi.

Since we'r on the subject, this was on eBay (in Gt. Britain) - looks cute...

[Por_sha911]

randy-do you have a link for that gauge?

[randywebb]

Ended w/o bids - item # 4636776092 - not sure what it really is before he sticks the crest on it (see his other items). Pretty tho.

Good Luck.

[DUK]

If you want the best go with Cecomp, If you want good enough go with longacre or intercomp.

[Por_sha911]

randy-thanks for the #. Probably a very cheap guage with a badge.
Thanks to all on their ideas on what a good gauge is. Seems to me that digital are nice but replacement batteries will cost more than the gauge. I have a hard time taking AccuTire seriously when they sell a "Digital Talking Pressure Gauge" (ebay #8063794863)
Now the question is HOW do you KNOW its accurate?

[bmgmd]

Don't knock the talking ones- they're for the older ones who have a hard time reading those small numbers!

I was considering a digital one with a back light since it's really hard to read the digitals sometimes when it's dark.

I'm not an engineer, but there is a difference between "accuracy" and "precision" (or what I've read above as referred to as "consistent").

A tire a gauge could be very precise (i.e., consistent) but inaccurate.

An example that I recall from college years ago uses the analogy of shooting an arrow at a target:

If the arrow hits the center red bullseye all the time, the shooter is accurate AND precise.

If the arrow keeps hitting the outer rim at the same location, say at 3 o'clock, the shooter is precise but not accurate.

[randywebb]

Warren gave the answer above - you compare the gauge to a primary standard, usually a manometer type gauge. OR you buy something that is NBS traceable (for scientific equipment).

But as a post above notes, the actual accuracy is not really that important as long as it is reas. close - say within a 3 psi. What you want is to be sure you are w/in the tire's load capacities and overall pressure range. THEN, tune the front & rear for the handling you want. Long a go, Todd Serota told me to use 30 or 32 F/34 R and that works well for the street.

Then you are only concerned with 'consistency' by which teh poster above meant repeatability - the liklihood that an instrument will give the same reading when it is measuring the same value over and over again (e.g. what if the instrument drifts over time; has random variation; is affected by radio waves; gives different outputs based on temperature effects...). This is all something scientists have worked out over the years. If people want more info, I can post some stuff on it.

[randywebb]

oh yeh - engineers may do things a bit differently -- the above is for scientists, esp. based on what chemists & physicists do