In our shop we used to have a Topeak SmartGauge for checking tire pressure. That thing died an unfortunate bike shop death, and we replaced it with an SKS Airchecker. There are some downsides to this unit (namely it seems to auto power-off before you can check the 2nd tire often…), and lately I’ve started to doubt it’s accuracy.
We recently ordered some Prestacycle Prestaflator Go USB-powered pumps, and I’ve been testing one in my personal garage for a bit. This thing seems to regularly pump tires up about 5 psi higher than my SKS Airchecker gauge reads. Begging the question: which gauge is correct? I’d be happy to have a pretty accurate digital tire pressure gauge to compare it against, but it’s dizzying trying to determine which number to trust.
It seems the Topeak gauge, and a slightly updated one are back in stock at Q. We’ve ordered a few more, so we can compare then. Until those arrive from Colorado, I’d still love to hear the take of others on this forum about this topic. Gracias.
I have a Topeak Digital Shuttle pressure gauge. I have compared it with several other pressure sensors/gauges (Quarq TyreWiz tire pressure sensors, Outrider tire pressure sensors, the OG Fumpa electronic pump) and it is accurate. One feature I like about the Digital Shuttle is the pass-through function. By connecting one end of the gauge to a pump and the other end to a valve, you can use the Shuttle to display tire pressure while inflating.
I have the Fumpa gauge and really like it. For road tires it’s usually within 1-2psi of my pump and TireWiz sensors, so I assume all of them are accurate enough for my purposes.
I’m a fan of the Digital Shuttle Gauge also because of that pass-through feature. Great if traveling and all you have is a hand pump in the hotel, and don’t want to use a loud e-pump.
First I’d ask the question what you mean by “accurate”?
A calibrated gauge against a known ISO -standard could be accurate, which would of course depend on the level of accuracy needed (± 1psi, 0,1bar, 10psi?). But that is not what you’re discussing.
What you want (and I think need most) would be gauges that give the same reading and some test for this by comparing the gauges. This would make life with several gauges easier.
But they could all be +0,3 bar and you wouldn’t realize this in this way.
I think that is no big deal, as the correct pressure for a given rider is individual and most of them will own a gauge that reads differently than the one in the shop.
Another point would be safety concerns with TSS setups, where a calibrated gauge allows you to go nearer to the max pressure of the system.
So what to do?
Shop for gauges that give the same reading? This could be achieved by a proper calibration. That will of course add to the cost.
Or compare your gauges against known calibrated ones and account for reading-differences, ideally across a range of pressures as this will vary IMO. At least for the safety-critical pressures.
Also if Dave tests this in the next roundup, he will have an experience on n=1 for each unit. But it will nevertheless be indicative of which will perform better than others
Am I the only one who finds it hard to use a presta tire pressure gauge without losing air trying to get it seated correctly? I end up trusting the digital gauge on my Lezyne pump bc I am annoyed using the tire pressure gauge: Topeak and SKS.
I have a few of the Topeak digital gauges. The pass through feature is great! It makes it so easy to compare the reading to the reading on the pump’s own gauge. I’ve also connected all the gauges in series to ensure they all read the same pressure.
If you really care you can build a home version of a dead weight tester, commonly used to calibrate pressure gauges. Basically you need a small pneumatic actuator and some known masses. If the actuator is 25mm ID, the bore area is 491mm^2.
1 N /mm^2 = 1MPa so for standard earth gravity (9.806 m/s^2) each 1 kg dead weight will give you 19.98 kPa, eg 20 kPa minus 0.1%. The error can be ignored since you don’t know how close to standard your local gravity is (it commonly varies by up to 0.5%)
A 15 kg mass is thus 300 kPa and two of them is 600 kPa, enough to give you a decent range for your calibration. Check the weights first, most gym weights are nowhere close to stated mass but most digital scales are very good.
Perfectly adequate pneumatic actuators are about $20 each on Aliexpress. eg:
Thanks for that, I didn’t know Wolfram had included that data.
There’s a very extensive set of data available for Victoria where a large scale survey of local gravity was completed last year: Airborne gravity survey
If you use a decent set of digital scales the error is cancelled out since they measure force not mass.
Actually not. Usually the plunger will come very close to falling under its own weight. If not, add weights until it starts to fall and that’s your zero point.