Caravan Tyre Valve Problem
So, back on the subject of tyre valve stems! This picture shows a caravan wheel on which the valve has been fitted with an after-market tyre pressure monitoring sensor (the big lump on the top of the valve stem). This type screws on to the end of the stem. It depresses the valve core to allow the unit to monitor the pressure. I have mentioned before that devices that fit on to the end of a valve stem in this way can - if not sealing correctly - allow air to escape causing a deflation. In the particular case the device caused a different problem. Look at the base of the valve stem and you will see a split. The other valve on the opposite tyre had fared worse and the split had gone through the rubber and alowed the air to escape causing a deflation. What was happening was that the weight of the tpms unit combined with the rotation of the wheel when the caravan was being towed created centrifugal forces that stressed the valve stem causing it to fail. Luckily the flat tyre occurred whilst parked and I spotted this one on the basis of if it happened on one side it will happen on the other. So, there you go - a device meant to alert you to low tyre pressure actually causes the problem it was meant to detect.
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