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Longacre Pro Precision Tire Gauge

Longacre Pro Precision Tire Gauge

Tool Review

by Ryan King

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I'm gonna share a little secret with you: I've wanted a nice, high-end tire gauge for nearly three decades and I've never bought one.

I long ago learned that precise tire pressure is essential for extracting maximum performance out of a car both in drag racing and road racing. I also found out that keeping the tires at the correct pressure means more precise and predictable drivability both on the road and on the track.

In fact, I can often tell if even one tire is off by only half a PSI — whether I'm racing or just taking a nice leisurely drive on the open road.

The truth is that tire pressure gauges aren't all created equal. And I don't just mean durability and longevity, I mean that accuracy right off the shelf can be off by as many as several PSI, depending on the quality. I'm pretty lucky that the cheap $12 tire gauge I picked up at the local parts store a few years ago was any good to begin with, but it seemed to be fairly accurate based on the way the Cobalt SS/SC drove. What with the factory recommended cold tire pressure being 32 PSI and the fact that the persnickety Michelins on it at the time worked at exactly that tire pressure as read by that gauge — even a half-PSI in either direction caused the handling to becoming erratic and difficult to correct.

That left me with the question: what gauge should I get?

Ideally, if I could afford it, I'd be tempted to adapt an NIST traceable certified pressure gauge for checking tire pressure — but we're talking major bucks — up into the $1,000+ range.

Although not certified, another option would be a high-end, carefully calibrated, temperature-adaptive digital race gauge capable of reading tire temperature and self-correcting so that the tires are filled to the same pressure regardless of environmental temperature or tire warmth.

Again, we're talking major bucks in the range of several hundred dollars.

So, what did I decide to do? I ended up going for the best mechanical dial tire gauge I could find.

Enter the Longacre Pro Precision Tire Gauge.

Its range is ideal for the Cobalt SS/SC — as well as the rest of my cars — with 0-60 PSI, incremented every half-PSI. The large dial face means it's easier to accurately see the needle reference to the marks on the face.

What makes 0-60 PSI ideal, you ask? A pressure gauge is most accurate in the middle of its range. In the Cobalt's case, that's 32 PSI — nearly right smack dab in the middle of 0-60.

Why a dial gauge and not a digital gauge? I don't want to have to deal with batteries. I just need a simple gauge that works.

Why this gauge? Longacre Racing Products has a stellar name in professional racing and they advertise this gauge as being accurate to within .5%. Not 5%, point-five-percent. As in, half a percentage point. There are a number of high-quality tire pressure gauges advertised at around 1.5-3% accuracy, so this thing is supposed to be supremely accurate.

Since I don't have an NIST traceable certified pressure gauge to test it against, I won't be able to tell you just exactly how accurate it is, but we're going to test it against both my old parts store gauge and my hyper-sensitive hand gauge to see how close it comes to perfection.

Perfection being how close it gets to setting the Pirellis to 32 PSI and optimum handling as compared to the parts store gauge reading.

What, might you ask, does a gauge of this caliber set a person back? Longacre sells them directly for $180 a pop as of this writing.

That's right. To get this level of accuracy, you'll need to part with two Ben Franklins.

If you think there must be a cheaper place to pick up one of these whiz-bang tire pressure diviners, there was. I picked up mine at Amazon for just under $169, but it's no longer on the site directly from Amazon — you may be able to find it from another retailer, though.

I tried to nab it from a parts supplier — you know, to help support the industry in this modern age of massive online retail juggernauts — but both Summit Racing and Jegs were selling it for the same price as Longacre, and I really did have to scrape hard to put together the scratch to buy this thing.

I should probably mention this isn't the kind of gauge you toss into your glove box or tool bag. It's too large and it needs to be better cared for than that. It's a serious instrument intended for competitive racing. For me, it will be used solely in my shop and kept in its hard case in a temperature and humidity-controlled environment.

Ha.

Okay, I still don't have a shop.

However, that's the purpose of the Longacre Pro Precision Tire Gauge for me. It won't be used for traveling. It'll set tire pressures precisely at home and I'll probably continue to use the cheap parts store tire gauge on the road — provided its accuracy is adequate.

Enough of this jack-jawing, let's get on with the pretty pictures and the testing!

Assembly Procedure

It Comes in a Box

It Comes in a Box

Like many products sold, the Longacre Pro Precision Tire Gauge is packaged in a box. Which, is how it arrived to me. The box isn't huge, but may be larger than you'd expect for a tire gauge. The reason is that the gauge comes in a padded hard case to keep it safe. Photo: Ryan King, 2019. Click image to enlarge.

Easy to Be Hard

Easy to Be Hard

This is the silver hard case freshly removed from the minimally decorated white cardboard box it's packaged in. It measures about 14 3/8"x11"x3 1/2" — not including the carrying handle. It's really quite nice, with riveted and chromed steel corners, molded aluminum edges, and hard plastic panels. Photo: Ryan King, 2019. Click image to enlarge.

Padded for Its Protection

Padded for Its Protection

Ta da!

Here's the Longacre Pro Precision Tire Gauge sitting in its nicely padded cell. This thing comes well packaged. Longacre is serious about this gauge — and I appreciate the fact that they take their high-quality products seriously. Not simply because of presentation, but because I can easily keep such a sensitive piece of equipment safe once I get it out of the packaging. Realistically, having to source something to keep this bad boy in would be a pain in the rump and I might not get it done, so my investment could be lost fairly quickly if it were dropped or something were dropped on it. Now it can sit on a shelf and remain there without fear of damage. Photo: Ryan King, 2019. Click image to enlarge.

The Whole Enchilada

The Whole Enchilada

This is the Longacre Pro Precision Tire Gauge in all its glory. It's got a 4.5" gauge that's almost 2" deep, and a 17" hose with two optional air chucks: one ball and one angle. You may also notice the dual air pressure relief buttons under the gauge head. One is for fast release, one is for slow. Designed and engineered for 0-60 PSI testing with half-PSI incrementation, combined with the large dial gauge, it makes for easy, accurate reading. As you may have surmised, even if you would be willing to mistreat a $180 gauge by trying to stuff it in your glove compartment or in a toolbox or bag, its size makes it a challenge to easily store like that. Those reasons — cost, care, and size — are why I'll only use it "in shop." Going on the road will require a more compact solution. Photo: Ryan King, 2019. Click image to enlarge.

Gauging the Gauge

Gauging the Gauge

Let's take a close-up look at the Longacre Pro Precision Tire Gauge. As already mentioned a few, the gauge is marked every half-PSI and the 4.5" head is protected by a removable rubber bumper. Photo: Ryan King, 2019. Click image to enlarge.

Glowing

Glowing

Like Longacre's other dial tire pressure gauges, the Pro Precision features a glow-in-the-dark face. I don't foresee using it in the dark, but If I do, it glows bright enough to read easily. Photo: Ryan King, 2019. Click image to enlarge.

Putting It to Work: Testing the Cobalt's Tire Pressure

Craftsman IR Pyrometer

Craftsman IR Pyrometer

Tire temperature: it's critical to tire pressure.

If you remember back to your study of physics, you know air expands as it gets warmer. When air expands within an enclosed space, it increases air pressure. Thus, as the tires get warmer for whatever reason, air pressure increases, changing the shape of the tire (although, radials do not change size by a significant amount), increasing its resistance to distortion from driving forces, and altering the size and/or shape of the contact patch on the pavement.

In order to make sure I'm comparing apples to apples, it's important to verify all the tires are the same temperature, which is where my old Craftsman IR Pyrometer comes into play. Although not as fancy or expensive as high-end pyrometers — and very likely less accurate — it should do the job for comparing tire temperature consistency from tire to tire for this review.

In case you were wondering, tire pressure versus temperature is calculated using the Ideal Gas Law, which, because radials don't change significantly in size (thus, volume) and use the same gas, the law can be used with sufficient enough accuracy for gauging tire pressure changes in relation to temperature. Without getting too technical, the Ideal Gas Law is based on four other laws which explain the relationship of the five factors in the Ideal Gas Law. Those factors are temperature, pressure, volume, quantity of gas particles, and a gas constant. As you'll note, I listed those factors in ascending order from least to most obscure. Don't worry about them, they aren't important for this explanation. Here's what is important, if you use the Ideal Gas Law to calculate tire pressure changes to temperature changes, as the NHTSA states on safercar.gov, it's about 1 PSI of change for every 10°F temperature shift. In Longacre's literature, they say to use .8 PSI for every 10°F change. For this review, I'm going with 1 PSI, because I can easily gauge a half-PSI shift for every 5°F — which is the smallest increment marked on the gauge.

All that means is, unless one tire is demonstrably warmer or colder than the others, there shouldn't be an issue — combine that with the fact that tire pressure recommendations are provided for cold, un-run tires, and you get the reason why it's important to test not only when the tires haven't been run, but when they haven't been exposed to sunlight. Especially when they all haven't been exposed to the same amount of sunlight. Photo: Ryan King, 2019. Click image to enlarge.

The Cobalt SS/SC Driver Front Side Tire

The Cobalt SS/SC Driver Side Front Tire

The day was heavily overcast and sitting stably at 60°F. The tread of the Cobalt's driver side front tire was 67.2°F, stone cold. The sidewall was 68°F. Longacre recommends taking the reading from the tread. Although I couldn't find an explanation on their website, my educated guess is that it's more accurate for gauging the temperature of a tire that's been run.

Now it's time for the first test.

The cheap parts store tire gauge read 30.75 PSI after pushing it onto the valve stem, struggling to get a solid seal, and waiting a few seconds for the needle to settle.

The Longacre Pro Precision Tire Gauge read 31.75 PSI. The needle also settled instantly and the chuck was easier to get on the valve stem accurately without losing air pressure.

As you can see in the photo, the gauge is big — it just fits in my hand and I have good-sized hands. Photo: Ryan King, 2019. Click image to enlarge.

I'm Going to Pump You Up

I'm Going to Pump You Up

Another important player in this test is my trusty Ryobi 18V One+ Dual Function Inflator/Deflator. It's cordless and allows me to set tire pressures on the cars without requiring a plug-in.

As I mentioned in the Bench Racing post, Fussy Tires, I don't have access to a good air compressor or a reliable power source to plug one into and the Ryobi Dual Function Inflator/Deflator has filled the bill admirably around my driveway — side note: I'd really, really like to be able to say shop.

Using the Longacre Pro Precision Tire Gauge, I corrected the tire pressure to exactly 32 PSI with just as much ease as it was to read the initial pressure. Both the fast and slow pressure release buttons work great to accurately set the pressure with easy precision.

Having never used a gauge of this quality, I am genuinely amazed at its ease-of-use — even if I can't measure its accuracy against a certified pressure gauge, it's obvious from the start that this is a high-quality instrument. No, this isn't a sales pitch, this is me sharing my genuine awe.

One down, three more to go. Photo: Ryan King, 2019. Click image to enlarge.

The Cobalt SS/SC Passenger Side Front Tire

The Cobalt SS/SC Passenger Side Front Tire

The passenger side front tire on the Cobalt registered at exactly 31 PSI with the parts store tire gauge. The Longacre Pro Precision Tire Gauge read 31.25 PSI. This time, only a quarter-PSI separated the two. I attribute this to the inconsistency of the seal I got with the parts store gauge.

Sadly, my old tire gauge is only five years old, but it both struggles with sealing on tire stems and it quit holding pressure readings a few years ago.

I also checked the temperature with the Craftsman IR Pyrometer. The tread sat at 66.7°F — one half-degree difference between the two tires. Using my understanding of the Ideal Gas Law, I used the Ryobi Dual Function Inflator/Deflator and Longacre Tire Gauge to set the pressure to 32 PSI.

FYI, there was no difference to the ease with which the gauge worked between this tire and the first.

Why no difference in tire pressure? As mentioned above, the half-degree lower temperature means the tire pressure in this tire is less than 1/10th of a PSI different from the first — not only is it out of the half-PSI adjustment range I set for this test, above, it isn't easy to adjust for, nor is it necessary to be that accurate in my experience. Photo: Ryan King, 2019. Click image to enlarge.

The Cobalt SS/SC Passenger Side Rear Tire

The Cobalt SS/SC Passenger Side Rear Tire

The test on the Cobalt's passenger side rear tire was nearly identical to that of the passenger front tire. The reading for the parts store gauge was 31 PSI, the Longacre Pro Precision Tire Gauge showed 31.25 PSI.

The only difference for this test was the tire tread temperature which read 65.7°F — 1°F lower than the passenger front and 1.5°F cooler than the driver side front.

With only a slight temperature difference well below the 5°F threshold, I kept this tire's pressure the same as the others at 32 PSI — and just as it did adjusting the previous two tires, the Longacre Gauge performed flawlessly.

I can get used to this. Photo: Ryan King, 2019. Click image to enlarge.

The Cobalt SS/SC Driver Side Rear Tire

The Cobalt SS/SC Driver Side Rear Tire

This tire was odd — but only because its tire pressure was exactly the same as the previous three. My parts store tire gauge measured 31 PSI, while the Longacre Pro Precision Tire Gauge measured 31.25 PSI.

The Craftsman IR Pyrometer measured the tire's tread temperature at 67.4°F and I used the Ryobi 18V One+ Dual Function Inflator/Deflator and the Longacre Tire Gauge to set it to match all the other corners at 32 PSI.

The Longacre Gauge continued to work with absolute precision and complete ease.

That was it, the Cobalt was done — no muss, no fuss. The experience was so great it was completely without drama or trouble. I've quite literally never set tire pressure so easily. Photo: Ryan King, 2019. Click image to enlarge.

Conclusion

Did it work?

Yes!

While the new Pirellis pictured throughout this test certainly had a lot do with it, this is unquestionably the best the Cobalt has ever driven and you might be skeptical, but based on my experience driving it before and after setting the tire pressure with the Longacre Pro Precision Tire Gauge, the precision set-up made all the difference in the world.

How much testing did I do to be certain? Over 1000 miles on flat roads, crowned roads, high and low-speed corners, reducing and increasing radius turns — uphill, downhill, flat, banked, and off-camber.

So, what made the difference? While my old parts store gauge happened to be close to the readings of the Longacre Pro Precision Tire Gauge for this test, my guess is that it has to do with how effortless it is to get a solid reading and set the pressure with the Longacre Gauge. In contrast, it's simply too easy to get a false reading with my old parts store gauge — and I know that from years of experience with it, struggling to get repeatable readings every time I attempt to put it on a valve stem.

Would I recommend the Longacre Racing Products Pro Precision 4.5" Tire Gauge?

With wholehearted enthusiasm — this thing is bloody amazing!

It isn't a solution for your glove box, nor a good match for the person who values dollars over performance — or quite frankly even necessary on the average commuter car — but damn, if it isn't the slickest tire gauge I've ever laid my hands on. And that includes the professional gauges I used when I worked as a tire technician many moons ago.

There isn't much else to say. I'm completely impressed. Although not cheap, it was money well spent — in my opinion, a great value.

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For more information contact Longacre Racing Products on the web at www.longacreracing.com or by phone 1.800.423.3110.

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