Snow tyre tread depth for effectiveness?

[joebongo]

I can't readily find a decent answer to this question so I thought I'd ask the PH collective.

I have to transport my father in law (who has a natty combo of advanced Parkinson's and dementia which has over the Christmas stay made my wife realise he really needs to be in a care home asap but that's another story), from near Lincoln to Evesham tomorrow.

The snow is falling and we have 1.5in so far. I've taken the Primera for a spin to test out the snow tyres I have on it, they're last year's ones and have about 5mm tread on them.

I didn't waver once and saw a few FWD stboxes slip about so followed them to see if I would too but I didn't.

But what is the minimum tread depth required for full effectiveness on a snow (not winter) tyre? They're only Nankang Snow SV2s but perform amazingly on both my Jag and the Nissan and if needed I have a brand new set waiting to be fitted in the garage but life got in the way the last few weeks (and to be honest saw no need whatsoever to even consider fitting them).

To paraphrase Samuel L Jackson, I positively, absolutely have to regain my sanity and take him home tomorrow if at all humanly possible.

[mwstewart]

It's around 4" deep along the edge at the moment - do you have a plan B? We're indoors at the mo and it doesn't look like our guests are going anywhere soon.

Sorry about your Dad.

[MondeoMan1981]

Pretty sure my old Fulda winters had 6mm and I didn't get stuck once.

[joebongo]

mwstewart said:

It's around 4" deep along the edge at the moment - do you have a plan B? We're indoors at the mo and it doesn't look like our guests are going anywhere soon.

Sorry about your Dad.

Thanks for your concern.

Plan B is hire a private ambulance or taxi.

Plan C is hire a helicopter.

Plan D is put him on a sledge warmly wrapped and pull him myself.

[bigfatnick]

I had some winters on my old bmw that only had about 3mm and they were will brilliant in the snow. I think it's the tread design (with the sipes) rather than the depth that does the work.

[IanMorewood]

5mm should be plenty, 3mm is usually when tyre places advise to change tyres.

[hdrflow]

Winter Tires Explained - Bridgestone Blizzak WS80: http://youtu.be/8OifbH5siF0

Great video I think

[Robert Elise]

bigfatnick said:

I had some winters on my old bmw that only had about 3mm and they were will brilliant in the snow. I think it's the tread design (with the sipes) rather than the depth that does the work.

true, but the sipes need more depth to work. Winter tyres have 2 wear markers: the legal limit of 1.6mm and approx 4mm for limit of effectiveness in winter conditions. In most situations i would push past the 4mm marker though, obviously in summer you keep going until 2mm
if you have 5mm it won't be tyres that are your problem. Good luck!

[mwstewart]

joebongo said:

mwstewart said:

It's around 4" deep along the edge at the moment - do you have a plan B? We're indoors at the mo and it doesn't look like our guests are going anywhere soon.

Sorry about your Dad.

Thanks for your concern.

Plan B is hire a private ambulance or taxi.

Plan C is hire a helicopter.

Plan D is put him on a sledge warmly wrapped and pull him myself.

Godspeed.

[joebongo]

Thanks for the responses, they're very useful. I might, just for sts and giggles, get the new ones put on in the morning before I depart although it sounds very much like I don't need to. I can always put the old ones back on and use them up as my spring/summer boots for the Nissan.

It's stopped more or less here now and there's about 1.5-2in tops so fingers crossed the weather forecasters have got it sufficiently wrong.

[rallycross]

5mm! Of course they still work well ( ie much better than normal tyres in snow).
My last set was still a big improve run over the normal tyres at 3mm.

[Charlie Boy]

Nokian suggest you need to change at 4mm to be effective in winter conditions...

[Motorrad]

4mm as already stated. They still work better than summer tyres down to 2 and a bit in my experience.

[Nigel Worc's]

There is absolutely no snow in Worcestershire that I am aware of, just so you know.

[joebongo]

To close this one off I went with the old tyres on, had no issues whatsoever and there was no snow south of brum really.

When I got back the wife was quite ill with a chest infection and I had to do a run to the local (45 mins away) primary care centre. So a double test which was passed with flying colours.

Now I've got it and my son has as well. The joys of Christmas :-)

Edited by joebongo on Sunday 28th December 08:22

[loskie]

4mm. I think that is the legal minimum in parts of Europe. Hence the large amount of use tyres on Ebay with this tread depth. Damned dangerous IMHO and likely to provide a false sense of security.
Which is why in the spring if the tread is getting low I will keep them on all summer and scrub them down and then scrap.

People by and large do not understand winter tyres here in the uk.

[JMGS4]

loskie said:

4mm. I think that is the legal minimum in parts of Europe.
People by and large do not understand winter tyres here in the uk.

Correct, 4mm tread depth minimum in Austria and Switzerland...... they're useless with that anyway!!!

[HannsG]

I bought some 17" rims with 5.5 worth of tread left. I'm hoping the M3 will be fine.

[AnotherGareth]

JMGS4 said:

loskie said:

4mm. I think that is the legal minimum in parts of Europe.

Correct, 4mm tread depth minimum in Austria and Switzerland...... they're useless with that anyway!!!

The minimum for winter tyres in Sweden is 3mm. See www.etyres.co.uk/winter-tyres-law.

[talksthetorque]

One of the reasons that snow tyres work in low temperatures is that the compound stays soft when it gets icy.
Having said that, I'd swap the new ones on, as you'd be kicking yourself if you did get stuck with the current tyres, even if the new tyres possibly would not have got you through either.
Plus the fact your FIL has a daughter who is your wife and might not be too pleased if 'you thought you'd be fine as some random strangers in the Internet said so'