Checking tyre pressures by looking is a useful as not bothering at all.
When you can see the cheek of the tyre bulging the pressure will be well down.
Nothing you can do about it other than checking with a pressure gauge, a pain in the backside if you have to take plates/spats off but that is the way it is.
Ignore it at your peril.
It is amazing that those tyres last as long as they do if you consider the stresses and strains put on them.
HTH
FD