Turns out the pencil type pressure checker wasn't that far off, I went to a gas station and had them pumped, they were all in the low 20s, oops! But why did the checker pop a 40 reading initially? It made me doubt all the rest of the measurements.
Shitty TPMS just measures differences between them so I got no warning.
Anyway, I pumped them to 33 at the front and 31 at the back. Reminder, they are 195/55 R16. Thoughts? It's free to pump them in my country, most gas stations have pumps.
The TPMS on your car is an indirect system that monitors the rotational speed of the wheels via the ABS sensors. It‘s purpose is to warn of a sudden loss of pressure in (usually) just one tyre - e.g. where the tyre has become damaged / punctured. If this happens, then the wheel with the damaged tyre will rotate at a different speed to the other wheels, and a low pressure warning will be triggered. If all tyres have lost equal pressure, then all wheels will still be rotating at the same speed so a low pressure warning won’t be triggered by the TPMS. That‘s why IMHO it’s important to check your tyre pressures manually on a regular basis - and carry out other checks at the same time, such as the general condition of the tyres and your under bonnet fluid levels (oil, coolant, screen wash). That way you can spot any problems and deal with them there and then or at the earliest opportunity.
Setting tyre pressures shouldn’t really be guesswork as there’ll be a recommended tyre pressure for 195/55 R16 tyres on your model of
Ibiza. My VW has a
sticker on the lower section of driver’s side B pillar which provides details of recommended tyre pressures - the owners manual for your car shows that the
Ibiza’s tyre pressure
sticker should be in the same location;
There may also be a ‘comfort’ tyre pressure setting for your car if you find the recommended pressure gives a ride quality that is a little too firm, although if you’d been running pressures of low 20’s for some time, then even the comfort setting may initially give the impression of quite a firm ride.
Bearing in mind you’ve been running your car with a very low tyre pressures, I would recommend you also check the tyre tread depth at different points across the width of each tyre. The tread depth should be pretty much the same across the entire width of the tyre, but with excessively under inflated tyres, they may have worn unevenly (worn more on the outer tread sections than the middle tread section), especially if your tyre pressures have been at low 20’s psi for some time.