Having changed a few tyres in the last week and being told that, while using the tyre removal machine, to keep well clear of the valve because of the sensors, I was intrigued as to how car tyre pressure sensors work, given there are no wires. I never knew they're part of the valve.
It transpires than there are two methods modern cars use to sense tyre pressure.
- The valve can contain a pressure sensor, the data from which is transmitted wirelessly to the car's computer. The sensor is powered by a lithium battery with a 5-10 year lifetime, which is far longer than the average tyre. Some sensors use the wheel's rotation to constantly keep the battery charged.
- The other method is derived from measuring the rotation speed of the wheels; a wheel which has a slightly deflated tyre rotates faster than a fully inflated wheel and the difference is used by the car's computer to calculate the pressure.
Amazing, ain't it?
Just looking at a tyre with the Mk I eyeball has usually been enough for me; however, just before Christmas I used No.1 Son's Mercedes CLA to go and collect No.2 Son from university in Winchester and hit a pothole with quite a bump.
I thought nothing of it (being used to my all-forgiving Ford Galaxy), but within a few miles I noticed a dramatic drop in the pressure of the tyre than had hit the pothole. The bump had actually bent the rim of the wheel, resulting in the tyre no longer seating correctly and pressure being lost. It was enough to return back immediately and get the Galaxy.
Being a Mercedes, I thought repairing the wheel would cost an arm and a leg, but was surprised to find that a bloke in Swindon could do it for £70, which was a steal given the fact it looked beyond repair to me.
Hay thought tyres were checked by a small rodent within the tyre wearing a hat with a torch on it.
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