Looks better than my rear tire and I rode in the rain yesterday. I typically don't replace tires till on the wear indicators. Its what the individual is comfortable with IMHO. Do what makes you feel safe.
1 mm left of tread is the time I prefer to replace my tires.
I ride in the rain like just I drive a car in winter on icy roads. There are lots or variables but a rule of thumb is to expect that a good tire on normal wet roads will provide about 70% or normal traction.
Only Ayrton Senna understood all there is to know about tires and racing in the rain.
The necessary depth of thread grooves relates to the depth of water on the road. A damp road--not so much. A puddle--you need more groove depth. There is no yes-or-no answer to whether your tires are safe in the rain.
The tire engineers I've spoken with say that there is no sudden drop-off point in the wet traction. As the tread wears the wet traction drops off pretty much progressively.
Michelin's new Pilot Road 4 seems to be the best rain tire that fits our bikes.
For cars & SUVs, Michelin has an interesting tire development in their new Premier line with rain grooves molded to expand as the tire wears to reduce the loss of wet traction (but there is still a loss). Premier A/S | Michelin Tires
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