In a world of weight weenies and bike brand snobs it was only a matter of time before the amount of air in your mountain bike tires would be something to scrutinize to the finest detail. Back in the old days you would just pump up the tire until it felt right when you squeezed it and then hit the trail. And if it was too much air or not enough air you probably didn't really notice the difference. And of course you were fine with it and still had a good time! But that was then and this is now.
This is where something like the Topeak SmartGauge D2 comes in handy. The D2 Smart Gauge is an electronic tire pressure gage that gives you the exact readout of your tire pressure on a digital display simply by pressing down on the valve stem with the gauge itself to get a reading.
The latest version of the gauge has what they call a SmartHead which allows the head to rotate in either direction. It's also designed to work with Presta and Schrader valves without changing any parts around. It can be used on tires as well as your suspension components to get accurate readings there as well. As for what types of measuring units it can display you can choose from psi, Bar, or kg/cm2. The maximum pressure it can read is 250 psi or 17 bar.
Using the D2 SmartGauge is pretty straightforward and all you need to do is press the head down on your valve stem once you change the valve type slider to the type you are using. You adjust the measurement unit by pressing the Unit button on the gauge and it will show you the unit being used as you cycle through them.
If you are using Presta valve stems make sure to unscrew the valve like you would if you were attaching your pump otherwise you won't get any kind of reading. Once you press the gauge down on the valve stem you will hear a beep when the pressure has been read and it will show right on the gauge. You don't have to worry about only being able read the pressure while its attached to the valve stem because once you remove the gauge it will keep the reading on the display.
The yellow air release button on the side is meant to fine tune your tire pressure so if you overfill it and want to release pressure slowly simply press this button until the pressure goes down to the level you desire. In order to have the pressure shown on the display you will need to press the Tune button before using the yellow air release button. The Tune button allows the air pressure to be read constantly instead of just once when you attach it to your valve stem.
The SmartGauge D2 takes a standard CR2032 battery which is included and should last a long time. The gauge will shut itself off after about 30 seconds of not being used so you don't need to worry about forgetting to turn it off after using it and wasting the battery. And if you care about its weight in case you want to carry it with you it comes in at 95 grams.
Overall the Topeak SmartGauge D2 seems to work very well and the accuracy seems to be pretty consistent as well. We have compared it to a Topeak JoeBlow Pro floor pump and the pressure comparison between the two is pretty much spot on so we trust its accuracy. It's very easy to get a quick tire pressure reading before hitting the trail and be assured that it is accurate so for around $30 it's kind of a no brainer if you are one who cares about having accurate pressure readings for your tires.