Well, if it wasn't for COVID and working-from-home, I'd be driving 40,000 km per year. I rotate tires every 10,000 km and it pays, in particular when you can see how changing these effects tire wear, that is if you diligently record wear.
The following graphs show two tires, both where on the rear. The latest 'green' curve shows that there is something wrong with the rear left (tire 1 was on). Since I asked the workshop to do a wheel alignment in February, it seems the alignment is not correct.
In short: I observed that a tire on the front will wear the sides (top three curves on both tires), wheel the rear wears the middle. An I usually end up with an evenly worn tire on all four. [1, 2, 3, 4, at the x-axis indicate the grooves from the outside in of the tire.]
Once I discover too much wear on the outside, I lower the pressure by 2 PSI, which usually solves the problem. This also demonstrates how important tire pressure is.
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