Which pressure gauge to believe?

[scotsbikester]

I've got an SKS Rennkompressor - https://www.sks-germany.com/en/products/rennkompressor/ - and a Topeak digital pressure gauge - https://www.topeak.com/global/en/product/351-SMARTGAUGE-D2
The Topeak consistently reads 10 psi lower that the SKS. I know a bit of air will be lost taking one off and the other on, but that seems like a big difference to me. This is on Presta valves, inflating to about 50-60 psi (622-35 tyres).

Any ideas why, or which one to believe?

Thanks.

 

[Gillstay]

I use a Sheffield made pencil gauge to check a car tyre and then use that to judge everything else. The digital one I had proved to be way out. Despite being more expensive. Even a Dunlop pencil gauge I bought from an antique shop was much more accurate. A friend had the same result. Hope that helps.

 

[Gillstay]

Sheffield one was PCL. Just remembered.

 

[PapaZita]

A man with a watch knows what time it is. A man with two watches is never sure.

Clearly, you need a third pressure gauge.

 

[davidphilips]

Great floor pump but perhaps the gauge is not very accurate? would trust the pressure gauge more.

Have owned a few track pumps over the years and present one is a Bontrager but have found that the gauge reads about %10 high.

Bought as a spare a cheap track pump in Lidls for about £7 a few weeks ago, cheap pump with plastic barrel looks and feels flimsy but after trying it out have found it works really great and is almost %100 accurate, How long it lasts can only guess.

Only my view but track pump gauges may not all be very accurate but a pressure gauge should be, well thats my theory?

 

[PapaZita]

I think what’s probably most important is that any gauge gives consistent, repeatable readings. We rarely really need to know the absolute pressure value. Of course it can be useful, say if using an online pressure calculator, to be able to transfer those recommendations to your own tyres, but even then, I consider those values as a starting point for fine tuning to taste.

 

[Mrs M]

If the road tyres feel “board hard” then that’ll do.
MTB a bit softer. 😀

 

[winjim]

A man with a watch knows what time it is. A man with two watches is never sure.

Clearly, you need a third pressure gauge.

You are Buzz Aldrin AICMFP.


View: https://twitter.com/TheRealBuzz/status/1680708340329099264?t=j-izQV4bD5mZFzmR1hTLhg&s=19


Personally I love my Rennkompressor but the gauge reads up to such high pressure that I think you lose some resolution and it's kind of difficult to read. But I'm not too fussy about exact pressures, plus or minus 10psi is fine by me.

 

[Profpointy]

I think what’s probably most important is that any gauge gives consistent, repeatable readings. We rarely really need to know the absolute pressure value. Of course it can be useful, say if using an online pressure calculator, to be able to transfer those recommendations to your own tyres, but even then, I consider those values as a starting point for fine tuning to taste.

Agree !

The "correct" pressure is some value that works best for your own weight and the smoothness of your local roads, giving you most speed on smooth tar but minimising lost effort in excess bounciness. The number on the gauge which matches this ideal derived from experience is what you then use. It doesn't matter than much if 8 bar on the dial is really 7 bar on a properly calibrated gauge. It only really matter that the reading is consistent.

It's quite hard to properly calibrate a gauge as an ordinary citizen doesn't generally have access to a standard or known calibrated gauge.

Now that said, if two or three gauges give much the same number, then they are likely not far off

 

[Cycleops]

If the road tyres feel “board hard” then that’ll do.

I have a feeling that by the end of this thread I'm going to be bored stiff.

 

[Mike Ayling]

I use a Sheffield made pencil gauge to check a car tyre and then use that to judge everything else. The digital one I had proved to be way out. Despite being more expensive. Even a Dunlop pencil gauge I bought from an antique shop was much more accurate. A friend had the same result. Hope that helps.

I use a Zefal Mechanical guage.

 

[slowmotion]

To get a consistent level of bounciness/firmness from your tyres you will also need a good quality barometer and reference thermometer.

 

[Jameshow]

Blackburn basic pump does the job for me 80psi unloaded 100 on rear loaded (25-28mm)

 

[scotsbikester]

Well, that's 10 minutes of my life I won't get back. But interesting, and the question is answered.

So, I found not one, not two, but THREE simple mechanical auto based tyre pressure gauges (schrader, obviously). Two pencil type, one rotary. Plus my Topeak digital.

Tried them on a car tyre. Some variance there, but it was about 15psi, so needs air, it turns out. And maybe that low it gets dodgy.

Tried them on another tyre. They all read practically the same, around 31/32 psi, including the Topeak. So in the range they are intended for (at least the car ones) it looks like they are accurate, or at least inaccurate by the same amount, which seem unlikely.

Tried the SKS Kompressor on the same car tyre - sure enough, 40 psi. So it looks like the SKS reads about 8 or 9 psi high. Which doesn't matter as long as I know. I still might write to them to ask if there's any way to calibrate/replace the gauge.

 

[winjim]

Tried the SKS Kompressor on the same car tyre - sure enough, 40 psi. So it looks like the SKS reads about 8 or 9 psi high. Which doesn't matter as long as I know. I still might write to them to ask if there's any way to calibrate/replace the gauge.

AFAIAA every part on a Rennkompressor is replaceable which is one reason I love them so much.

Edit: from your link above it's part no 3037. Can't speak for the calibration though, maybe they'll send you one FOC if you ask.