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  • FIRST POST
    • barnaclebill
    • By barnaclebill 15th May 17, 11:27 AM
    • 230Posts
    • 124Thanks
    barnaclebill
    Free air
    • #1
    • 15th May 17, 11:27 AM
    Free air 15th May 17 at 11:27 AM
    Used Sainsbury's air line for a few months, when it was out of use I started going to Morrisons as you get a free pin when you buy fuel.
    On Friday I needed fuel and was passing Sainsbury's and noticed the air supply was renewed so just did two tyres that usually need a top up, noticed that the car before me was taking a long time to do his tyres and when I started I could not see the gauge from my position but I had set the pressure at 31 psi and in the end it beeped and I then did the other wheel. Saturday I drove about 60 miles ok, on Sunday on a long journey doing 70 on the motorway I got the 'check tyre pressure' warning.
    Pulled into a garage and used my pencil gauge to check which tyre was the problem, the first I checked was the first I had done on the air line on Friday, it was 44psi same for the other one I had done on Friday, the two I did not do were 34psi.
    Looks like the new air supply in Sainsbury's is faulty, I will be passing there today and will let them know, could cause a problem for someone.
    Think I will go back to using my own compressor.
Page 1
    • Jackmydad
    • By Jackmydad 15th May 17, 1:00 PM
    • 316 Posts
    • 235 Thanks
    Jackmydad
    • #2
    • 15th May 17, 1:00 PM
    • #2
    • 15th May 17, 1:00 PM
    You wouldn't expect it to be that far out would you? There always used to be warnings in the motoring and national press at one time about the dangers of inaccurate service station "free air". One I remember had gone round comparing, and some were way out.
    Nothing to be done but tell them of course.
    • Iceweasel
    • By Iceweasel 15th May 17, 1:40 PM
    • 4,167 Posts
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    Iceweasel
    • #3
    • 15th May 17, 1:40 PM
    • #3
    • 15th May 17, 1:40 PM
    Likely you didn't notice that the previous user had selected bar instead of psi - I always do.

    3.1 bar equals 44psi

    An easy mistake to make if you still use and think in old units.
    • neilmcl
    • By neilmcl 15th May 17, 1:45 PM
    • 9,853 Posts
    • 6,856 Thanks
    neilmcl
    • #4
    • 15th May 17, 1:45 PM
    • #4
    • 15th May 17, 1:45 PM
    Think I will go back to using my own compressor.
    Originally posted by barnaclebill
    A bicycle track pump is all you'd need and not as hard to use as some might lead you to believe.
    • neilmcl
    • By neilmcl 15th May 17, 1:46 PM
    • 9,853 Posts
    • 6,856 Thanks
    neilmcl
    • #5
    • 15th May 17, 1:46 PM
    • #5
    • 15th May 17, 1:46 PM
    Likely you didn't notice that the previous user had selected bar instead of psi - I always do.

    3.1 bar equals 44psi

    An easy mistake to make if you still use and think in old units.
    Originally posted by Iceweasel
    ^^ Absolutely this. I always use the bar setting, probably confuses some using it after me.
    • barnaclebill
    • By barnaclebill 15th May 17, 1:53 PM
    • 230 Posts
    • 124 Thanks
    barnaclebill
    • #6
    • 15th May 17, 1:53 PM
    • #6
    • 15th May 17, 1:53 PM
    After training engine cadets about pressure systems I am aware of bar to psi, please be advised that the start pressure was 20 psi and I increased it to 31 psi before use
    The pressures set cold at 31 psi would be about 34 psi hot after driving at 70 mph for some time so if set at 44 would have been 47 psi
    Last edited by barnaclebill; 15-05-2017 at 2:07 PM. Reason: explaining the set point at start
    • neilmcl
    • By neilmcl 15th May 17, 2:13 PM
    • 9,853 Posts
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    neilmcl
    • #7
    • 15th May 17, 2:13 PM
    • #7
    • 15th May 17, 2:13 PM
    Fair enough, we were only offering a possible cause, particularly if someone is in a rush or having one of "those moments" that we all have occasionally. Having said that an initial setting of 21 psi on the machine seems pretty low too for car, a more valid setting would've been 2.1 bar, therefore increasing it to 3.1 thinking it was 31 psi isn't outside the realms of reality.

    You'll only know for sure if you go back there.
    • AdrianC
    • By AdrianC 15th May 17, 2:33 PM
    • 14,785 Posts
    • 13,139 Thanks
    AdrianC
    • #8
    • 15th May 17, 2:33 PM
    • #8
    • 15th May 17, 2:33 PM
    After training engine cadets about pressure systems I am aware of bar to psi, please be advised that the start pressure was 20 psi and I increased it to 31 psi before use
    The pressures set cold at 31 psi would be about 34 psi hot after driving at 70 mph for some time so if set at 44 would have been 47 psi
    Originally posted by barnaclebill
    ...but if the gauge was a little out, it could have reached what it thought was 3.1bar a little early, leading to the heat increasing the pressure to 44psi.

    But, tbh, if you're losing THAT much air, I'd get the actual problem sorted, rather than just working around it and needing to reinflate the tyres regularly.
    • Tarambor
    • By Tarambor 15th May 17, 8:36 PM
    • 1,017 Posts
    • 693 Thanks
    Tarambor
    • #9
    • 15th May 17, 8:36 PM
    • #9
    • 15th May 17, 8:36 PM
    After training engine cadets about pressure systems I am aware of bar to psi, please be advised that the start pressure was 20 psi and I increased it to 31 psi before use
    Originally posted by barnaclebill
    You sure? I don't know any cars which have 20PSI as their pressure but I do know plenty do have 2.0 bar, it is the recommended tyre pressure for one of my cars. With 3.1 bar being the 44 PSI you measured it is strongly suggesting that the gauge was in fact displaying bar and you've misread it.

    Just because you've trained people about pressure systems and know the difference it doesn't mean you can't be having an off day and just missed the fact that the letters to the right of the number didn't say PSI. Easily done given the vast majority of the people are going to use PSI so you're used to that being what they are when you go to use them.
    • Iceweasel
    • By Iceweasel 16th May 17, 8:21 AM
    • 4,167 Posts
    • 3,016 Thanks
    Iceweasel
    I've used Sainsburys air pumps and never seen an option to select between bar or psi.
    Originally posted by Norman Castle
    Old ones don't have a bar/psi option - but the newer ones do.
    • boliston
    • By boliston 16th May 17, 8:24 AM
    • 2,322 Posts
    • 1,881 Thanks
    boliston
    I would have thought kilos per square cm would make more sense
    • Iceweasel
    • By Iceweasel 16th May 17, 8:39 AM
    • 4,167 Posts
    • 3,016 Thanks
    Iceweasel
    I would have thought kilos per square cm would make more sense
    Originally posted by boliston
    I'm guessing that you are saying that in jest - but the numbers would be pretty much the same as 1 bar is equal to 1.01kg/cm2

    The bar is a widely accepted unit - although most folks would be more familiar with the smaller sub-unit the millibar used in all our weather forecasts.

    It would be pretty strange/confusing to hear the weather forecasters using psi.
    • Car 54
    • By Car 54 16th May 17, 8:47 AM
    • 2,120 Posts
    • 1,352 Thanks
    Car 54
    I would have thought kilos per square cm would make more sense
    Originally posted by boliston
    No, a kilo is a unit of mass, not of force.

    The appropriate measure would be Newtons per square metre, or Pascals.

    1 bar = 100,000 N/m2 = 100,000 Pa
    • Andy L
    • By Andy L 16th May 17, 9:41 AM
    • 8,411 Posts
    • 6,705 Thanks
    Andy L
    Think I will go back to using my own compressor.
    Originally posted by barnaclebill
    Are you sure that's any better callibrated than Sainsbury's?
    • barnaclebill
    • By barnaclebill 16th May 17, 11:13 AM
    • 230 Posts
    • 124 Thanks
    barnaclebill
    Update, pressures were my fault, returned to Sainbury's to check gauge and all working ok so must have been my mistake. Thanks to all who pointed out this was the likely answer and sorry I found it so hard to accept.

    As to some later posts, all of the ships I sailed on built after 2007 had gauges in Mpa with some lower pressure in Kpa so it could come into use here. I recall driving an old BMW that had an oil pressure gauge in pascals
    • AdrianC
    • By AdrianC 16th May 17, 11:28 AM
    • 14,785 Posts
    • 13,139 Thanks
    AdrianC
    If only this country could extract its collective head from its collective rectum, and actually finish the process of metrication that was originally timetabled to be completed over 40 years ago...
    • Iceweasel
    • By Iceweasel 16th May 17, 11:36 AM
    • 4,167 Posts
    • 3,016 Thanks
    Iceweasel
    If only this country could extract its collective head from its collective rectum, and actually finish the process of metrication that was originally timetabled to be completed over 40 years ago...
    Originally posted by AdrianC
    I started my teaching career in 1970 - never once did I use any Imperial units in class.

    But having said that I do believe that for the plumbing industry BSP (British Standard Pipe) measurements were adopted as an SI Metric? standard.

    So for example a shower fitting from anywhere in Europe will fit in the UK.
    • wongataa
    • By wongataa 16th May 17, 12:58 PM
    • 1,022 Posts
    • 550 Thanks
    wongataa
    I started my teaching career in 1970 - never once did I use any Imperial units in class.

    But having said that I do believe that for the plumbing industry BSP (British Standard Pipe) measurements were adopted as an SI Metric? standard.
    Originally posted by Iceweasel
    Indeed it has. The pipe thread standards are:
    ISO 7
    ISO 288
    EN 10226
    • neilmcl
    • By neilmcl 16th May 17, 2:55 PM
    • 9,853 Posts
    • 6,856 Thanks
    neilmcl
    Update, pressures were my fault, returned to Sainbury's to check gauge and all working ok so must have been my mistake. Thanks to all who pointed out this was the likely answer and sorry I found it so hard to accept.

    As to some later posts, all of the ships I sailed on built after 2007 had gauges in Mpa with some lower pressure in Kpa so it could come into use here. I recall driving an old BMW that had an oil pressure gauge in pascals
    Originally posted by barnaclebill
    Good of you to come back and admit that, not many would've.
    • DarkShadow
    • By DarkShadow 17th May 17, 2:29 PM
    • 142 Posts
    • 60 Thanks
    DarkShadow
    So for example a shower fitting from anywhere in Europe will fit in the UK.
    Originally posted by Iceweasel
    After the EU referendum, it will no longer fit. Atleast we got our whatever back.
    Bank accounts
    Santander : 14 year relationship, 0 problems to date.
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