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Manufacturer Page: https://www.topeak.com/global/en/product/1395-SMARTGAUGE-D2X

In 1995, when I was pedaling across America, the tubes in my tires had Schrader valves, which should have made it easy to top them up with air at gas stations, since motor vehicles also use Schraders in their tires. But because the pump I carried on the bike had no gauge, and because I had no separate air gauge, I usually just squeezed my tires between my thumb and forefinger. It took a great deal of effort to achieve high pressure in the tires with my on-bike pump, so if the tires felt reasonably firm, I didn’t do anything further, and I just occasionally used a gas station pump.

Here’s something I wrote in my book about that trip, Roll Around Heaven All Day: “At a Farmington [Missouri] gas station, I used the air hose to top up the pressure in my tires. All bike tires lose a little air over time. Although I had tested my tires daily by feel, I hadn’t added any air since Frisco, Colorado, where I initially pumped them up to 100 psi. When I checked them with [the gauge on the station’s pump] now, I found the front tire still at 85 psi and the rear at 65. I had no flats at all on this leg of my trip.”

I now know the tire squeeze isn’t very accurate, and that I was lucky not to have flatted on that leg.

Keeping your bike tires at the right pressure is important. Too much pressure results in a jolting ride and too little slows you down and makes you more susceptible to flatting. Good floor pumps have built in air gauges, but a lot of the mini pumps we carry on the bike still do not.

That’s why I was glad to find Topeak’s Smartgauge D2X, which is a step up over their previous D2 model, which itself is quite good. The head of the D2X rotates a full 360 degrees for easy access to your valves, whereas the D2 swivels, but not all the way around. (I prefer to think of the D2X as having a body that rotates 360 degrees, since the head doesn’t move once it’s latched onto a valve.) Like its predecessor, the D2X works with both Presta and Schrader valves — you choose which with the flip of a switch; there are no internal head parts to change. The easy-to-read lighted digital readout shows your air pressure in your choice of psi, bar or km/cm2,and it turns off automatically, so it doesn’t run down the battery.

Unlike many gauges, this one has a button for releasing excess air, allowing you to get to your preferred pressure exactly. I don’t like that when using the air-release button, the display doesn’t automatically change; you have to press the pressure-reading button, which causes the display to update the pressure reading. It would be smoother if it would do this without having to press the additional button. But this is a small inconvenience, and the positive features outweigh it.

At less than two ounces (which is less than the D2), the D2X Smartgauge is a good addition to your on-bike bag or your bike toolbox.

Stan Purdum has ridden several long-distance bike trips, including an across-America ride recounted in his book Roll Around Heaven All Day, and a trek on U.S. 62, from Niagara Falls, New York, to El Paso, Texas, the subject of his book Playing in Traffic. Stan, a freelance writer and editor, lives in Ohio. See more at www.StanPurdum.com.

Wow, another device that takes a battery. I can see it now, someone reaching for their trusty PSI gauge before going on a ride, and is greeted with a blank screen. Avoid the blank screen and get a mechanical gauge instead, the screen is never blank, never needs a battery, will work forever. AccuGage makes mechanical gauges that are more accurate than digital gauges, and they last forever.

I keep a D2 at every location where I keep bikes, now 4. I find it to be an amazing accessory because of it’s small (convenient) size, light weight, precision and durability (never needed a battery). Once, I bought one that turned out to be inaccurate; I contacted the maker, was told to send it back and a new one arrived in a week, no extra cost. How do you beat that?

Good technique is critical when using a separate pressure gauge on narrow (higher pressure) road bike tires. Burping even small volumes of air while checking can significantly drop their pressure.

Checking tire pressures by feel takes regular practice- like airing to a known pressure then feeling the tire. Some riders I know are uncannily good at it.

I recently “re-tired” several of my bikes, upgrading from Maxxis Re-Fuse (they refuse to go very fast without a lot of work) to Continental GP 5000 on a couple of bikes and the very nice and less expensive GrandSport Race on two other bikes. I run latex tubes in everything so have to pump the tires every time I ride (well worth the hassle.) I also became a convert to lower tire pressures — love that, too. So it seemed wise to get a Topeak D2 to get everything started on the right foot, or spin.

Together, these changes have made one of the biggest overall improvements in my bikes. It takes a bit to get used to the D2 but it is much more accurate than any pump gauge I have ever used, and certainly more accurate than my thumb. I, too, was a bit put off by the button pushing ritual to release air in a controlled way – push Re-set, take the initial reading, then remove the gauge, press Re-set and Tune and reattach the gauge to fine-tune the pressure. That creates three chances for a bit of air to escape. Then I discovered that by pressing Re-set and Tune before taking any pressure readings, I was able to take a reading and then bleed off air with only one move. Fast and accurate. Just remember to inflate your tires to more than your desired pressure.

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