Left my Yeti at a local garage today to have the old winter tyres taken off and new ones put on.  When I returned they said they hadn't done as asked as they thought there was still too much tread on the old ones!  They measured 5 mm on the rear set and 5 on one front and 4 on the other.  While I appreciate their honest consideration for the weight of my wallet (they are thoughtful and friendly from my past experience, hence my trust in their professionalism) I'm not sure they're right on this occasion.  They suggested the old tyres would last the winter out.  I do approx. 15 -20,000 miles a year.  I thought 4mm was the absolute minimum recommended for winter tyres and I had intended to keep one of the 5 mm rear tyres for a spare.

 

Your opinions re tread depth on winter tyres would be welcome.

On my 4 season tyres they have 2 sets of wear bars one at the normal legal min, and a higher set at 4mm for which is the recommended min for snow,  Have your winters got the higher wear bars on them.

The wear bars on winters tyres are set at 4mm, though that is only relevant (I presume) where winter tyres are mandatory. As the UK doesn't require their use then the standard 1.6mm limit will be the deciding factor. Obviously if you intend taking it abroad where winter tyres are regulated, then get them changed.

 

I've noticed a little bit of lost traction on my winter tyres in the last few weeks. The traction control light has flashed a few times and there's been a little bit of wheel spin under hard acceleration on wet tarmac. That's not something I've been able to do in previous years (though admittedly this is the first winter with a remap, so torque is higher than before). They are down to 4.5-5mm and will be replaced after April. By then they'll have done 17k or so, over three winter seasons. That's better than similar priced budget summer tyres I had on my old Octavia, which had got to the 1.6mm limit in around 14K!

On my 4 season tyres they have 2 sets of wear bars one at the normal legal min, and a higher set at 4mm for which is the recommended min for snow, Have your winters got the higher wear bars on them.

The Nokians on SWMBO's Leon are the same.

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I changed my winters around just under 4mm so the garage is probably right you can still probably get another winter out of them as it doesn't snow that often in the uk and I don't think it is that important compared to countries that have continuous months of snow.  I guess if you get lots of snow near where you live it's worth changing them for the peace of mind for optimum grip in the snow.

The tyre manufacturers recommend changing winter tyres at 4mm, and many of them also recommend changing summer tyres at 3mm as they become less effective in the wet.  If you've still got 5mm of tread depth and the sipes in the tread blocks are still there you should be OK. 

At about 4mm you see the sipes nearly gone, so you will lose a lot of the benefit of them and the will just be softer normal tyres. There is a reason you will find a lot of not entirely honest sellers advertising winter tyres with 4mm of tread remaining, even on these forums. Click on the pictures and they will be all but bald (sipe wise).

It's not really a matter of legality here, it's whether you want them to work as intended.

 There is a reason you will find a lot of not entirely honest sellers advertising winter tyres with 4mm of tread remaining, even on these forums. Click on the pictures and they will be all but bald (sipe wise).

 

They get very upset if you point it out though.

Thanks for all of the replies - really helpful.  The tyres are Vredestin Wintrac Xtremes and they do have the double tyre wear 'blocks' in the treads.  There's still a whisker (1mm?) above the 'winter' block in the most worn tyre so I'll bear with them for now. 

 

The tyre manufacturers recommend changing winter tyres at 4mm

 

FWIW the legal requirement varies across Europe. For example, in Sweden winter tyres can no longer be used in the winter months when the tread gets down to 3 mm.

 

At about 4mm you see the sipes nearly gone

 

Last April my front Vredestein Snowtrac 3 tyres were almost all the way down to the 1.6 mm tread wear indicator and the sipes were still showing. In November I replaced couple of Hankook Optimo 4S tyres at about 2mm and the sipes had started to disappear.

 

I reckon that while winter (or all-season) tyres will have lost much of their effectiveness for use in cold and wet wintery conditions by the time they get down to 4 mm, they're probably still more effective than equivalent summer tyres all the way down to 1.6 mm.

I'd change at 4mm but by then you'd probably have noticed they weren't as good any more. Bear in mind that they start with 8mm.

I've just swapped back to the summer tyres today, and the Nokians are still at 4.5-5mm - no obvious change since January. They've now done 18K, and it looks like I might get another season out of them, particularly if there is another snow no-show winter again. The sipes are still 99% there, along with the snowflake markers in the centre of the tread.

 

Oddly my summer tyres are down to 3-4mm, and they've only done 1K more. The wear is more towards the outside edge of the all tyres, so that might be the warmer weather allowing more enthusiastic driving!

Like others have said, the Nokian WRG2's on my MX5 have 2 sets of wear bars, one at 2mm and one at 4 or 5mm.

 

But the real indicator is the sipes - these give the nice edges to grip on ice, and by the look of it they go down to the higher wear bars.

 

So I figure when the sipes have gone, then the driving performance on ice will be less. But given the rubber and the rest of the tyre design, they'll be better than the summer tyres in colder weather (snowy or otherwise)