Tyre Pressure Low - No Warning Light

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angels1five
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Tyre Pressure Low - No Warning Light

Post by angels1five » Fri May 01, 2020 11:31 am

I thought my front near side tyre looked a bit low so I tested it and found it was down to 18.5. I checked the other front tyre and that was down to 21.5.

I thought there was a warning light that would come on when the pressures were too low? I've only owned the car for about five weeks and as we've been locked down have done hardly any driving.

What could be the problem? Anyone have any idea?

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st3v3cx-3
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Re: Tyre Pressure Low - No Warning Light

Post by st3v3cx-3 » Fri May 01, 2020 3:22 pm

There is a warning light to indicate low pressure in one or more of the tyres, but it doesn't use a special valve on each wheel but it monitors the pressure indirectly using data sent from the ABS sensors i.e. a tyre with low pressure will rotate more slowly (?) and thus be different to the others. Thus the vehicle needs to be driven for the system to work. Plus the system has to be initialised - before the car is driven - once one or more of the tyre pressures have been changed. It will then take a few miles to operate fully.

So I 'm assuming your tyre has just gone down whilst the car has not been driven and the above would apply. If you'd driven your car with the tyre at that lower pressure then the indicator would have lit up after a few miles.

The ABS sensor was in use for cars up to July 2018 per that owner manual so later cars may have gone over to the more sophisticated special valve method which I believe would indicate a low pressure as soon as the ignition is switched on.
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hsdejong
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Re: Tyre Pressure Low - No Warning Light

Post by hsdejong » Fri May 01, 2020 10:26 pm

st3v3cx-3 wrote:
Fri May 01, 2020 3:22 pm
i.e. a tyre with low pressure will rotate more slowly (?)
At a lower pressure, the circumference becomes a little smaller, making the wheel rotate a little faster.
Apparently the average difference in rotation speed between the wheels is measurable.
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