Free air

barnaclebill
barnaclebill Posts: 411 Forumite
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in Motoring
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.
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Comments

  • Jackmydad
    Jackmydad Posts: 9,186 Forumite
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    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
    Iceweasel Posts: 4,708 Forumite
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    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
    neilmcl Posts: 19,460 Forumite
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    barnaclebill wrote: »
    Think I will go back to using my own compressor.
    A bicycle track pump is all you'd need and not as hard to use as some might lead you to believe.
  • neilmcl
    neilmcl Posts: 19,460 Forumite
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    Iceweasel wrote: »
    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.
    ^^ Absolutely this. I always use the bar setting, probably confuses some using it after me.
  • barnaclebill
    barnaclebill Posts: 411 Forumite
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    edited 15 May 2017 at 2:07PM
    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
  • neilmcl
    neilmcl Posts: 19,460 Forumite
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    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
    AdrianC Posts: 42,189 Forumite
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    barnaclebill wrote: »
    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
    ...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.
  • System
    System Posts: 178,093 Community Admin
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    barnaclebill wrote: »
    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

    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
    Iceweasel Posts: 4,708 Forumite
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    Norman_Castle wrote: »
    I've used Sainsburys air pumps and never seen an option to select between bar or psi.

    Old ones don't have a bar/psi option - but the newer ones do.
  • boliston
    boliston Posts: 3,012 Forumite
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    I would have thought kilos per square cm would make more sense
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