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Discussion Starter · #1 ·
I bought a brand new SmartGauge D2 from Amazon, and compared its reading to my other pressure gauges around the house. I have two digital gauges (marketed for car tires) and two JoeBlow floor pumps with built-in analog gauges. Three of these four gauges agree with each other within a PSI or so; the fourth (the analog gauge on the more beat-up floor pump) reads a little low.

The SmartGauge D2 consistently reads about 10% lower than my three gauges which agree. 27 instead of 30 PSI, 28 instead of 31. This discrepancy holds no matter which order I use the gauges in. It doesn't matter whether I'm measuring bike or car tires.

Thinking I probably got a bad unit, I exchanged it for a new one. The replacement gauge came today, it does the exact same thing, and I don't know what to believe.

Folks out there who have the SmartGauge D2 and another gauge, can you please compare them and share your result? Thank you :)

(I don't need replies just to tell me that I can find the pressure that "feels right" and the exact number on the gauge doesn't matter. I'm a nerd, I want to measure pressure accurately.)
 

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Mine is consistently low when compared to the mechanical gauge on my shock pump. 10% is about what I am experiencing also.

The inconsistency isn't too frustrating on tires. I run them at around 18 - 22 PSI reading on the Topeak. I squeeze test the tires before riding and add pressure if needed Since tires are low pressure, I don't have to worry about losing too much air when I disengage the tire pump.

HOWEVER, the discrepancy drives me crazy when it comes to shock pressure. I will pump my shock to, say, 200 PSI reading on my shock pump, disengage the pump -- which inevitably results in some lost air -- then check with the Topeak and it will read around 180 PSI. So, I am left wondering, Did I lose 20 PSI when I disengaged the shock pump? I doubt it, but shocks are so high pressure that it's possible. It's gotten so frustrating that I am considering buying a new shock pump that releases more easily. The one I currently have screws off the valve, and I am wondering if there is a better pump/valve interface that releases from the valve more quickly and efficiently, without losing air.
 

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you don't lose pressure disengaging a shock pump, they are designed to retain air in the shock...all you hear is the air in the hose letting loose...the shock valve is already closed before that happens.

attaching the topeak to the shock, or any gauge to check it.... or attaching the pump and you see the pump gauge read pressure....that is when you lose pressure in the shock itself. and if it has a small air can like a rear shock, a little hiss means a lot of PSI

go by feel with shock and shock pumps. pump it, note what the shock pump says, go ride. note how it went. add more or less pressure and note what it says. if the shock pump is technically inaccurate it does not matter, what matters if it is consistently inaccurate. that way whatever you note based on what the dial says and how it felt...use those numbers and it will be good for how you like it and able to be repeated if you use the same pump and same gauge.

trying to fight technical accuracy in PSI is kinda useless without spending thousands on scientific equipment that will be 100% accurate for lab work...and you need to have those calibrated often by other more expensive equipment. not worth it imho unless you build and design shocks yourself, or happen to work in a lab with that gear already around and won't cost you anything to use.
 

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you don't lose pressure disengaging a shock pump, they are designed to retain air in the shock...all you hear is the air in the hose letting loose...the shock valve is already closed before that happens.

attaching the topeak to the shock, or any gauge to check it.... or attaching the pump and you see the pump gauge read pressure....that is when you lose pressure in the shock itself. and if it has a small air can like a rear shock, a little hiss means a lot of PSI
Yes, this came up when I mentioned it on a different thread. What I find concerning is that sometimes it's a quick burp of air when I disengage the pump and other times it's a longer sigh of air, and when I validate using the Topeak, there is a difference in lost pressure between the burp and sigh, with the sigh being lower pressure.
 

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that may be an issue with the pump gasket or oring...somehow.
try lubing it a little bit with shock oil but just a tiny wipe with a q-tip

the chuck has a long nose and stops depressing the valve well
before the pump chuck gasket lets go of the seal. replace the seal ?
 

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Mine reads low also compared to other gauges I have available to me. This is not an issue for tires as long as it is consistent, but was worrisome for use on my fork and rear shock. I only depend on the shock pump gauge and sag now for suspension setup.
 

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My digital Topeak D2 SmartGauge also consistently reads right about 10% lower than my analog Meiser Accu-Gage. I'm glad I saw the other responses in this thread because I've always wondered if the Topeak gauge was reading low.

I actually hate using the Topeak gauge. You have to push it dead straight onto the valve or you get inconsistent readings. I end up having to check and recheck the result like half a dozen times or more just to end up believing what the correct reading is.

My Meiser Accu-Gage however reads consistently the same every. damn. time., without ever worrying about having seated it properly onto the valve stem.
 

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Discussion Starter · #10 ·
Three clear confirmations (@Prognosticator, @NJPhil, @A. Rider) and zero clear dissents! Still a tiny sample size, but this sounds like a possible systemic issue with the SmartGauge D2.

Is there a better presta-valved digital gauge out there? The Meiser Accu-Gage sounds great for measuring pressure but too heavy and fragile to carry on a ride.
 

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Another vote for 2 - 3 psi low. My 2 floor pumps will say 25 psi and the Topeak will read 22. At least these things are consistent.

My eyes are going bad and I find the topeak easier to read than my old analog and cheapo digital gauges. So keeping it and just knowing I need to +2 to whatever its saying.
 

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Same ten percent versus my Meiser’s as well. Now that doesn’t mean one is more right than the other. But they always read ten percent off. That said, after three Topeak’s going dead in four months, I just use the Meiser units now. Don’t have to fiddle as much to get a correct reading and I don’t know wtf im
Doing that kills the Topeaks, but they don’t last long if I ride with them in my pack.
 

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If accuracy is what you're after, get a certified gauge. Keep in mind that pressure gauges are similar to torque wrenches in that they usually only meet their claimed accuracy in the upper XX percentage of their range.

McMaster has a pretty wide range of gauges and you can probably find one that you could replace a stock gauge with.
 

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Recieved as Xmas gift that I asked for, checked shock w my Specialized Shock Pump showing 170 put the Topeak on and it blew the screw top off and a few pieces strewn on my floor. Amazon replaced very quickly, so I used new one on tires and it was showing 2-3 lbs low compared to my floor pump w gauge. Checked Shock w Shock Pump again at 170 and the D2 wouldn’t read over 100 took it to my LBS and let them play w it ( maybe it was me doing something wrong) same results it was way off on the Shock by like 60-70lbs. I got it to read 110 on my wife’s bike that was set to 130 w Pump. But it’s not working properly so I guess it’ll be returned. Too bad was hoping it would be handy to travel with, but think it’s too wide of range to measure anything close to accurate. Will stick to Shock Pump and Auto gauges for tires. Anyone had decent readings off their shocks with the D2?
 

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Recieved as Xmas gift that I asked for, checked shock w my Specialized Shock Pump showing 170 put the Topeak on and it blew the screw top off and a few pieces strewn on my floor. Amazon replaced very quickly, so I used new one on tires and it was showing 2-3 lbs low compared to my floor pump w gauge. Checked Shock w Shock Pump again at 170 and the D2 wouldn’t read over 100 took it to my LBS and let them play w it ( maybe it was me doing something wrong) same results it was way off on the Shock by like 60-70lbs. I got it to read 110 on my wife’s bike that was set to 130 w Pump. But it’s not working properly so I guess it’ll be returned. Too bad was hoping it would be handy to travel with, but think it’s too wide of range to measure anything close to accurate. Will stick to Shock Pump and Auto gauges for tires. Anyone had decent readings off their shocks with the D2?
No. Just return it while you still have the chance. I also got one as a Christmas gift a couple years ago and I never use anymore, shortly after realizing it's so damn inconsistent.
 

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My D2 is being a pain in the ass, sometimes it turns on, sometimes it doesn't. Brand new battery and all. As others have said, it reads about 2-3psi lower than my floor pumps (one's digital, other is analog) as well as my digital shock pump.

Anyone find a better digital gauge?
 
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