Tyre Pressures

[OldBoyScout]

2 minutes ago, KenONeill said:

Er, 3 of us have independently calculated that the process as described doesn't go past 95% by volume. Since O2 is denser, I'd expect the percentage of N2 to be lower than than the volume.

Your calculations assume the tyre contains regular air at the outset. I am saying it already has a high nitrogen content having been filled with nitrogen prior to the demo.

 

[KenONeill]

On 21/08/2019 at 12:14, OldBoyScout said:

Your calculations assume the tyre contains regular air at the outset. I am saying it already has a high nitrogen content having been filled with nitrogen prior to the demo.

 

His process works for a 98% N2 fill, in principle; it's just that it doesn't work out with his stated method and pressures. OK?

[OldBoyScout]

2 minutes ago, KenONeill said:

His process works for a 98% N2 fill, in principle; it's just that it doesn't work out with his stated method and pressures. OK?

Yes, I agree. I was quoting 98%, as that was the value shown on the nitrogen meter in the video.

[benterrier]

What a bore this topic has become 😔

[Breezy_Pete]

So don't read it...

[OldBoyScout]

I have found this topic quite stimulating, and would guess that many members who have actually taken part in the discussion would feel the same. It has gone a long way from where it started out, and I have learned how the TPMS works and a bit about nitrogen. We have had a bit of disagreement, which I hope we have now resolved, and a bit of humour. 

[KenONeill]

Likewise; I was remembering stuff I'd not used since uni, and that's since the 1980s.

[Biggriff]

So my question is does the Octavia have a true TPMS tyre sensor set-up or is it just down to the ABS sensor picking up variances?   

[Ootohere]

The Octavia that can just show a TPMS warning, even which tyre has as basic as it comes, ABS sensor / system showing.

A car, any car or vehicle that can show The Pressure in tyres, temp etc has a different system.

[themanwithnoaim]

Just to close off the Nitrogen debacle 

 

1. Rightly or wrongly, dry gases are seen as more stable for tyres inflation 

2. Costco sell my prefered brand/size of tyres cheapest 

3. Costco ONLY Nitrogen fill their tyres.

 

Conclusion, my placebo has been massaged

 

When I commit to a high speed corner I don't wonder whether my tyres will do the job, I Fn KNOW they will, as proved by my continual fight with my Crew Protection opening the windows & pretensioning the seatbelts & I still haven't been in a bloody ditch yet.

 

Wherever or not it actually works, I have been given confidence in the tyres & car's capabilities.

 

@Biggriff sorry for the thread Jack but, no the O3 has no separate sensor it's all done by variances in ABS sensor readings.

[maffyou]

On 20/08/2019 at 13:52, Roottootemoot said:

 

 

“Nitrogen retailers - arseholes” 

 

Love that 🤣

[Breezy_Pete]

I love the whole video TBH. Unfortunately, there are plenty of people in this world who (and I quote verbatim one that I once met ) "don't believe in science".

They will always be the victims of the marketing people.

 

[Rodge]

On 17/08/2019 at 16:20, Gerrycan said:

A quick google search says pressure variance is 0.19psi per degree Centigrade so very nearly 2psi per 10 degrees C.

I forgot to account for absolute versus relative pressures. I worked from 10 °C is about a 3% change in temperature, which will give a 3% change in pressure, which based on 32 psi relative pressure (WRONG!) would give a change of about 1 psi. Using absolute pressure instead gives about 1.5 psi per 10 °C, starting from 32 psi. Starting from 40 psi gives your 0.19 psi per °C. (32 psi chosen as having been mentioned previously in the thread.)

The only time I've had a TPMS warning was when there was a screw in the tyre, although the tyre had not gone down.