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 Post subject: Re: Tyre pressures
PostPosted: Mon Nov 21, 2016 9:01 am 
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Enjay wrote:
Just to play Devil's avocado, advocaat, whatever ( :P ), given that 0.5 PSI is actually a pretty small value, I do wonder if nlel's gauge is accurately calibrated. I mean, when it's reading 31.5, what is the actual pressure in the tyre? Has the gauge ever been compared against a reliable standard? If not, all this worrying about 0.5 PSI might be irrelevant. Unless it was very expensive, I wouldn't hold that much faith in a home-user gauge being 100% accurate to 0.5 PSI.


According to Auto Express it was "faultless throughout the accuracy tests"

http://www.autoexpress.co.uk/accessories-tyres/45076/ring-digital-tyre-keyring-gauge-rtg4

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 Post subject: Re: Tyre pressures
PostPosted: Mon Nov 21, 2016 8:58 pm 
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Having now seen it and the price, I'm even more doubtful that it's spot-on accurate to 0.5 PSI.

That's not to say I think looks like a bad bit of kit (I'm sure it's very useful and easy to use) but it doesn't look like something that has been calibrated accurately enough for anyone to say hand-on-heart that their tyre pressure is accurate to one half of a pound per square inch (not that anyone needs to).

Although "The RTG4 was faultless throughout the accuracy tests" sounds promising, without knowing exactly what the accuracy tests were, I'm still sceptical. "Faultless" is a big claim. I'm not saying it can't be fully accurate, just that it strikes me as unlikely to be.

I'd like to find out what it reads when pressures are actually, and verifiably 30.0, 30.1, 30.2 (etc) (again, not that anyone really needs that level of accuracy in practical terms).


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 Post subject: Re: Tyre pressures
PostPosted: Mon Nov 21, 2016 9:01 pm 
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J15nel wrote:
I've forgotten what tyre pressures are thanks to this thread. I should really go out and check them but it's damn cold and they look round.

Oh no! I think something might be wrong with my tyres. They're not round. They seem to be a bit flat at the bottom. Image


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 Post subject: Re: Tyre pressures
PostPosted: Mon Nov 21, 2016 9:03 pm 
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This thread has out lived its novelty humor

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 Post subject: Re: Tyre pressures
PostPosted: Mon Nov 21, 2016 10:03 pm 
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Enjay wrote:

I'd like to find out what it reads when pressures are actually, and verifiably 30.0, 30.1, 30.2 (etc) (again, not that anyone really needs that level of accuracy in practical terms).


It's simple 30 would read 29.5, 30 PSI or 30.5 PSI

30.1, 30.2 would read either 30 or 30.5 PSI. I don't know whether it rounds them up or down but still should be within 0.5 PSI

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 Post subject: Re: Tyre pressures
PostPosted: Tue Nov 22, 2016 12:24 am 
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What I really meant was how would it fare against a machine that had definitely been calibrated to a high level of accuracy? For example, if it is meant to display, say, 30.5 when the true value is any of 30.3, 30.4, 30.5, 30.6 and 30.7 does it actually do that or is it off at all? I suspect it will be off, at least by a little (a negligible amount, but off never the less). So, if it was off by, say -0.2, when it was reading 30.5 the real value could be 30.1, 30.2, 30.3, 30.4 or 30.5. Not a big deal; in fact not a deal at all really. But the point is, you don't know because you don't have a calibration certificate (I assume).

However, your answer kind of illustrates what I was trying to get at. Even if it is "faultlessly" accurate, when the gauge is reading 30.0, you don't know if the pressure is actually 30.0 or where it is in a range of potential values from 29.6 to 30.4 - and that's if it is indeed "faultlessly" accurate. If it's out by even a little bit, you really don't know what the actual pressure is when the gauge reads 30.0 other than (just like any other gauge or air pump you are likely to use) being able to say, it's pretty close to 30 - as near as practical and possible anyway.

I'm not saying you shouldn't check your tyres. I'm not saying that you shouldn't try and get them as close to the specified pressure as possible and if you enjoy doing it and seeing how things seem to be changing from day to day, crack on (I actually do understand why someone might enjoy doing that). :) All I'm saying is that you seem to be worrying needlessly about trying to get the tyres pressurised to a level of accuracy that isn't particularly practical with the varied conditions that your tyres find themselves in and with a measuring system that may display readings in values of 0.5 PSI but you don't know how that level of granularity is calculated.


I guess, for me, a bigger question is why I typed so much about something I'm not even bothered about. Image I guess it's just that at my work I often come across people trying to measure stuff to a level of accuracy that is both unnecessary and not actually meaningful within the system that they are trying to make the measurements. Maybe I need to get out and check my tyre pressures to cool off or something - and it certainly would be cool: its about -2.456733 degrees C out there right now. I know, I checked it with a digital thermometer. ;)


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 Post subject: Tyre pressures
PostPosted: Tue Nov 22, 2016 12:27 am 
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 Post subject: Re: Tyre pressures
PostPosted: Thu May 24, 2018 2:52 pm 
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The owner of this well respected Smart car resource... https://www.evilution.co.uk/564

Describes the practice of "Over Filling."

"This is a neat little trick that increases MPG but decreases grip. The extra pressure increases the hardness of the tyre and reduces the contact patch on the road. This causes less rolling resistance but also less grip.

I have increased the tyre pressure to 36psi in my tyres that require 30psi."

There is no way I'd inflate any of my tyres to 6 PSI more than required, I don't care about extra mpg.

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 Post subject: Re: Tyre pressures
PostPosted: Fri Jul 06, 2018 12:43 pm 
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I have recently gone for a more solid drive at 35 psi. The trouble with 30/32 is the outsides are liable to wear. I am seeing mire favourable wear now and a solid drive is not affecting the crowns.


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