[Tannaton]

On winter tyres they regarded as "spent" when the tread drops below 4mm and many of them have additional tread wear indicators that indicate 4mm. However between 3 and 4mm they will still probably be much better than summers of any tread depth.

All seasons tyres have come on a lot in recent years and as has been said there are a number that carry the 3PMS symbol which effectively means they are classed as winter tyres.

Michelin Cross Climates are an example and get very good feedback from almost everyone on here who uses them. Vredestein Quatrac would be another.

I personally run winter tyres all year round on all my vehicles (Cooper Discover Winter on my XC60, Cooper WeatherMaster WSC on my Ford Ranger). We don't get snow that often but when we did earlier this year I quite enjoyed overtaking my colleague on the hill up to work who was in his Defender with Goodyear Wrangler on it. It's not just that I could pass him - I left him standing whilst having full control with no wheelspin or drama whatsoever. The small penalty in MPG would not be recovered by changing tyres twice a year.