When to replace tyres?

[culzean]

I agree that rubber compounds are better now, and actual condition may be more relevant than an arbitrary age. Especially if summer and winter tyres are swopped and  spend much of their life stored out of harmful sunlight.

 But they may still suffer from microcracking and deterioration , as can the rubber used in  tyre valves.

But do I have the skill  to spot serious degradation ? I would rather not find I was wrong  by a high speed blow out.   

I think 1.6mm is pushing your luck. Far more likely to aquaplane in the wet.   2mm is better.   
I'm skeptical about Michelins  claims, albeit lower  tread Michelins may still be better than other brands with more tread depth.  Sounds like a marketing strategy.

Narrower tyre sizes need less tread than wide ones - it is all to do with the distance the water has to travel to escape from under the tyre, the shorter the escape path the less likely tyre is to aquaplane, and on dry roads the less tread on the tyre the better.....

[Lord Voltermore]

Narrower tyre sizes need less tread than wide ones - it is all to do with the distance the water has to travel to escape from under the tyre, the shorter the escape path the less likely tyre is to aquaplane, and on dry roads the less tread on the tyre the better.....

Racing slicks! If only our weather was so predictable    I have a cunning plan. Variable minimum  tread depth based on tyre width 

I have read more than once, most recently in a post by Roman,  that wet roads significantly  increases fuel consumption on the Mk4 .Pushing water away must add a lot of rolling resistance . Probably true of all cars and tyres, but maybe the standard  eco tyres don't perform particularly well in this respect.  This, and reduced noise, is probably why Honda have stayed with 185 tyre width.   

[peteo48]

On the rain thing increasing fuel consumption EV owners of my acquaintance say heavy rain and surface water has a significant (adverse) effect on range.

[embee]

Pumping water generally takes a lot of power/energy. When roads are wet the tyres are simply water pumps, the faster you go and the more water on the surface the more power it takes. Hitting a deep puddle will slow a car quite effectively.

In engine development, traditional* dynamometers were simply water pumps in essence, you don't need a very big unit to absorb a coupe of hundred kW. Look at a boat outboard propeller, it's taking all the power of the engine, a 100bhp outboard prop will only be 150-200mm diameter. Water is heavy stuff to shift.

(*Most modern dynos are more commonly eddy current devices, and use water as a coolant).

[TnTkr]

But they may still suffer from microcracking and deterioration , as can the rubber used in  tyre valves.

But do I have the skill  to spot serious degradation ? I would rather not find I was wrong  by a high speed blow out.   

Blow out of a steel radial tubeless passenger car tyres without any clearly visible bulge or side crack is extremely unlikely. They just begin to leak.

[Kremmen]

This probably needs changing :