When to change new tires for my 2015 Toyota Prius? - with the penny test

[Davislasson]

I had a lot of difficulties due to the Covid epidemic, so I didn't have much time to be here. But recently, I've read articles about tire wear tests with the penny, but it seems Consumer Reports and others recommend changing tires sooner.
as https://tireer.com/penny-tire-test/
I know a lot of early change the tires here but who changes tires at ~5/32", 4/32" instead of 2/32"? From a safety perspective?

[FROSTYBALLS]

In the UK the minimum tread depth is currently 1.6mm - equivalent to 2/32". I tend to change when the tread depth hits 3mm (4/32") or slightly below. Think a lot of people now use a proper tread gauge, either analogue or digital, rather than the edge of a coin as these are more accurate.

Having said that the following article illustrates that Michelin doesn't support changing tyres earlier than the minimum tread depth, as it costs the owner more, increases carbon emissions, and doesn't improve safety - https://www.automotiveworld.com/news-releases/michelin-changing-tyres-3mm-unnecessary-costly-harmful-environment/

[Roy124]

And that minimum depth is across 3/4 of the centre and all round. 

Pleasing as it may be changing tyres at 1.6mm two other factors come into play. 

First is that it is better, and sometimes essential, to change both tyres  front or back, at the same time. 

The other is the time of year.  Approaching winter it may be prudent to change before the weather turns, though in UK in some areas it is much wetter. 

[xav]

No need to measure? There are wear indicators on all tyres for the 1.6mm minimum tread inside the deepest grooves of the tyres they are like small humps? when you reach this point is time to change them and as above do in axle pairs or replace all 4 with same tyre ideally? Having 2 different kinds of tread on 2 axle pairs can effect noise and how car drives ( more friction generated by one pair than the other pair) mpg can also be effected for the same reason 

[TonyHSD]

These wear indicators depth seems has been changed on newer made tyres and they are as described above 1.6mm instead of 3mm as had been for years, here I have pictures of older made tyres and more recent ones from 2020 and the indicators depth is obviously different. 👍 

[xav]

I was not aware that newer tyres are now like this? I'm sorry, learn something new every day thankyou for the info Tony