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Tyre pressure fluctuating - what's causing this please?

  • 09-12-2021 2:40pm
    Registered Users Posts: 147 ✭✭ homenotaway

    Hi all and TIA for any and all replies to my query.

    Yesterday the alarm sounded (and the light came on) that my left front tyre had decreased pressure. It was checked in a tyre shop, no puncture was found and inflated to 35 PSI. The alarm sounded again on the way back to the house, I measured it then and it read 27 PSI. This morning it is reading 38 PSI. I haven't driven the car yet today.

    Can anyone explain what is happening?


  • Registered Users Posts: 1,387 ✭✭✭ redcup342

    The air is expanding and contracting depending on the temperature outside.

  • Registered Users Posts: 5,367 ✭✭✭ kirving

    Did you measure it using a separate tool, or via the car's computer?

  • Registered Users Posts: 6,955 ✭✭✭ micks_address

    its not unusual for me to see tyre pressure lights on as temp drop in the autumn/winter..

  • Registered Users Posts: 214 ✭✭ pdpmur

    Tyre pressure gauges can be quite inaccurate. The ones attached to the ends of air lines that you would traditionally find in garages are notoriously unreliable. If you are making measurements with different gauges at different times then this could explain the big differences. If your car has a TPMS then the measuring valve could have become faulty.

  • Registered Users Posts: 4,426 ✭✭✭ maestroamado

    from what you say it appears you have a tester and tested with 2 times... it seems the tester dodgy...

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  • Registered Users Posts: 147 ✭✭ homenotaway

    Thanks all for your replies. I only bought the tyre pressure gauge yesterday evening. I tested all 4 tyres but the only one which tested differently was the one which triggered the alarm/light.

    A suggestion which was made by the tyre shop guy was that sometimes if a bearing is at fault the tyre pressure alarm is triggered.

    The car is 2017 if that's of any help 🤷‍♀️

  • Registered Users Posts: 5,185 ✭✭✭ zg3409

    Look at the door where it displays the recommended tyre pressures. Some cars display the recommended pressure beside the actual pressure. Put in 3 or 4 psi more than needed and ensure error goes away. Then you can put in the right pressure at a later date. If you fill tyres when wheels are warm from driving, it will drop when cold.