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Tyre pressure measurement

edited 22 September 2022 at 8:53PM in Motoring
55 replies 1.7K views


  • Car_54Car_54 Forumite
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    MalMonroe said:
    The reading on the OP pic is around about the pressure for the tyres on my car, I was originally told.

    I have a Toyota Aygo and just googled 'tyre pressure and size guide' for its year of manufacture -

    "165/60 R15, 2.3 bar or 33 psi, 2.3 bar or 33 psi"

    Thank you so very much.

    Without all the flim-flam, I believe that means the PSI (pressure per square inch) on a tyre gauge (but please don't make me use one) should read 33 and the radius of the tyres needs to be 15 inches. Nope, not gone metric there at all, then.

    My car is collected by the dealer every so often for an MOT and service and they tend to fiddle about with tyres and other things, wash it thoroughly and do a valet service, after which it is returned to me at my home - all nice and sparkly clean. What goes on behind the scenes is nothing whatsoever to do with me.

    Well, a court would not agree. You, as the driver - and only you - are responsible for the safe condition of your vehicle. An annual service isn't enough: tyres need regular checks for pressure and condition, and lights can and do fail.

    BTW don't rely on Google for tyre pressure info. You need to check Toyota's specifications (do you have a manual?) and also determine what size of tyres you actually have. And the15" in your example is the diameter of the wheel rim, not the radius of the tyre.
  • Smudge's_LotSmudge's_Lot Forumite
    79 Posts
    Part of the Furniture 10 Posts
    I am sure that all cars for over 10 years have a sticker in either front door inner surrounds that give the pressures required for various tyre sizes and weight loads.
    Have a look!
  • Grumpy_chapGrumpy_chap Forumite
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    MalMonroe said:
    the PSI (pressure per square inch) on a tyre gauge 
    pounds per square inch.

    MalMonroe said:
    I do know how to put petrol in, though because that is really handy to know.  Maybe even a splash of windscreen wash, at a push. . .   Well, after all, I'm a driver, not a mechanic.
    The current driving test requires a higher level of familiarity than that:
    Even if you are not concerned with passing the driving test, it is good to try to get someone to show you these items on your own car so that you know if you ever need to.  It might just one day mean you can continue with a journey more quickly and more safely than needing to wait for the breakdown service to assist.  You should, in any case, be making these check with greater frequency than at every service and that will help ensure the reliability and safety of the vehicle on the road.

  • Ibrahim5Ibrahim5 Forumite
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    Just memorize all the units of pressure and conversion factors. Job done.
  • sevenhillssevenhills Forumite
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    Car_54 said:
    You, as the driver - and only you - are responsible for the safe condition of your vehicle. An annual service isn't enough: tyres need regular checks for pressure and condition, and lights can and do fail.
    I was explaining to a female relative who has recently bought a 10+ year old Audi, about what the highway code says she should check.
    She doesn't know how to, she said, I explained that she is a teacher and she can learn.
  • zagfleszagfles Forumite
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    k3lvc said:
    Loved watching someone who should probably have known better trying to get their BMW tyre to 31 bar and wondering why the garage pump didn't go up that far - I kept a safe distance  :open_mouth:
    On a similar note I was behind someone waiting to use the air pump, she was taking ages with each tyre, so got out to check as I thought the machine might be faulty so not worth waiting. Turns out she was pumping each tyre up to a ridiculously high pressure which was why it was taking so long.
    She apologised and said she'd never checked her tyres before (!!) but was advised to by a friend. I questioned why she was going from about 30PSI to way over 50, which is ridiculous for a small car. Turns out she was using the pressure stated on the tyres - but that wasn't the recommend pressure, it was the max pressure the tyre can take!

  • victor2victor2 Forumite, Ambassador
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    Unfortunately, it seems that many "younger" drivers today have no idea how to do much maintenance on a car beyond putting petrol in it, and maybe water in the screen wash.
    A friend who is a mechanic had to recover a customer's car that had failed. It turned out the oil warning light had come on so the driver went to Halfords and bought 5 litres of the oil Halfords recommended, managed to find the oil filler and poured all of the oil in. It didn't go very far!

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  • chriswchrisw Forumite
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    sheramber said:
    For many years fabric was sold in inches width but meter lenghths.

    So bought x meters of 36 inch wide material.
    Timber is still sold like that. So you buy 1.8 metres of 4"x2".
  • oldagetraveller1oldagetraveller1 Forumite
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    "pounds per square inch."

    Being pedantic, it's pounds(lb)f/
    That was used, pre SI units, to differentiate between force and mass, mass = pounds(lb).
    Whereas SI mass = kg, force = Newtons. B)

  • edited 25 September 2022 at 5:53PM
    DanDare999DanDare999 Forumite
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    edited 25 September 2022 at 5:53PM
    Jenni_D said:
    shiraz99 said:
    Iceweasel said:
    Are we now metric - we've been metric since 1972. No school in UK has taught in Imperial since then.
    Yet we still measure distance in miles not km.
    Except in athletics ... I can't remember a Mile race for a long time. ;) 
    The London marathon is next week, run every year over 26.2 miles. 
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