The two best ways to determine if you SUV summer tyres are worn out, is by visual inspection and by measuring the tread depth. The first one, the visual inspection, should be done on a regular basis, just to check that your tyres look to be in good condition. Here you look for any visual damages, if the pattern still looks good and if the tyres look inflated. This will not take you too many seconds and can easily be done while you are at a petrol station filling up your car. You might as well look at other safety features, like are the lights ok, no visible damages to the car as such. This will give you a quick idea of the status of your tyres.
If you have the time it is always better to properly check the air pressure in the tyre, to ensure that the tyre pressure is correct. A faulty tyre pressure is bad for driving performance, for your road safety and is bad for fuel efficiency. It also causes the tyre to wear faster and more uneven, so with all this in mind, you should take the time to check it on a regular basis, so if not at every stop at the petrol station.
The second step, is checking the tyre depth, this can easily be done with for example a coin, where you press that into the tread depth to see how deep it goes. You should have at least 3mm of tread depth left to be on the safe side. If you don’t feel like checking all four tyres, check at least one of the front tyres and one of the back, as the wear may be different. This is also why it is recommended to rotate the tyres, by switching the front tyre to the back and vice versa. If you change to winter tyres, this would be a logical time to do it, if you don’t then you should plan to do it when the difference in tread depth is more than 2 mm. You can plan to do it every 8000 km, if you don’t want to keep measuring the difference.
Making sure that your tyres are in good shape and have the adequate tread depth is important and by rotating the tyres you save money by not having to replace the tyres prematurely.