Which pressure gauge to believe?

[All uphill]

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

Either that or you'll make a great comment and be all puffed up for the rest of the day.

Go on, try it - no pressure.

 

[Gillstay]

Either that or you'll make a great comment and be all puffed up for the rest of the day.

Go on, try it - no pressure.

Hard to gauge a good comment on this site !

 

[All uphill]

Hard to gauge a good comment on this site !

Some people have an inflated sense of their own wit.

 

[scotsbikester]

Thanks. Yes, the grandfathers axe/Triggers broom aspect of the pump is one of the reasons I bought it. Those gauges seem to be about £13. But as the pump is only a couple of years old maybe SKS might give me on. Or if it's a standard fitting, I'm tempted to replace it with something better and/or with a more suitable range for me.

Or I can just remember to subtract 9 psi.

 

[matticus]

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.

Buzz Aldrin always wore 3 watches for this reason.

These days he wears 4!

 

[GuyBoden]

I'm sure that my cheap 10 year old £5 Aldi track pump's gauge is more accurate than my old pressing the tyre with the thumb method.

 

[silva]

My rocket science:
- I push my palm against the tyres sidewall.
- If I can push it inwards over the entire palm width, then I pump more air in, until I can"t push it inwards anymore and note the gauge indication.
- Then I ride it, and if my rear tyre/wheel tends to slip sideways and stays on the low side of an elevated bicycle lane when I steer my front on it is signaling more pressure. If it rides too bumpy, I let some air out.
- If it was okay, I note the gauge pressure I had pumped it up to. for a next time to get ok in 1 time.
- If it wasn't, I add +'s to the figure I noted, every + is a pump stroke.
For ex, 4.5 bar, and I had to put 3 strokes extra in, I make it 4.5+++.
If I had to let out air, I put a - in front of the number, suffices because letting out air doesn't need any tools so not a hassle.

If I don't have a pump with gauge at hand, I just count the strokes and yellow tape the number on the pump.
For my 62 mm tyres it's some counting tho.

 

[Ajax Bay]

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

Let's explore this a little more to get an idea of range of variation (I am no expert).
Roughly air pressure varies a maximum of 5% above and 5% below 1000 mbar (UK) (14.5psi).
And temperature (for sensible cycling) varies about 10% (°K) (x − 273.15) °C
The pneumatic benefit of tyres depends on pressure of the tyre above 'grade' (current local atmospheric pressure).
So if you pump a tyre up to 100 psi (maths-easy, as reading on gauge) in the garage (say) at 288°K then how much will that vary?
Varying temperature: plus or minus 5%
Varying air pressure: up to 10% more or less if inflating tyre as deep low or mega high passes through.
Have I got that right?
For competitive triathlon efforts (TT easier), if an athlete wants a particular tyre pressure they are wise to take into account temperature changes between when they check and adjust at (say 6am before T1 closes) for a ride which may last 5 hours from 8am to 1pm and an air temperature which rises from 12°C to 30°C, such calculations are important (primarily to optimise rolling resistance and comfort). https://en.wikipedia.org/wiki/Ideal_gas_law

 

[slowmotion]

Varying air pressure: up to 10% more or less if inflating tyre as deep low or mega high passes through.
Have I got that right?

That's about right. "Normal" atmospheric pressure in taken to be 1013 millibars. During the Great Storm of 1987, it fell to 953. In 1902, Aberdeen experienced a high of 1053.

{ Useless facts courtesy of Dr Google. }