My method of monitoring the tyre pressures. These are valve covers which indicate RED when pressure drops below the set value of the caps, but are GREEN when up to the correct set pressure. These caps can be obtained in many different set pressures.

WARNING: It has been suggested recently that these monitors might not give the correct reading if the vehicle is left for any length of time. As when storing during winter!

I have found while the vehicle is in storage for about a fortnight, then checking tyres, the indicator is green yet the tyre pressures are well below the target indicated! It would appear that these indicators require regular running of the tyres to be effective.