Winter tyres - regulations and discussion

Transportation, Travel and Trips
81
There's a study out there somewhere done by Honda (if memory serves) which demonstrates how temperature and rubber compound influence braking distance; and they further developed a method to bench test and predict braking distance per compound at various temperatures.

Ah, but all tyres are the same say some, even summer tyres contain silica say others... et caetera et caetera ad infinitum.

To the skeptics, I recommend checking the treadwear index of their summer and winter rubbers. You will notice said index differs - hence you can safely assume that the rubber compound will differ as well.

82
I was going to post that I'm not putting on my winter tyres next month because I haven't been able to take them off this year as everytime I thought about it, it rained.

But now I have learned that winter tyres are really more snow specific and my summer (top of the range) tyres would have been better in the wet then the winter tyres I kept on. I won't make this mistake next year and thanks to the contributors of this thread for the education.

Next April Summer tyres go on regardless.

83
If you are a member of the TCS, or know one, they have their annual review of winter tyres in this months membership magazine. I get the French version and I presume they have the same article in the other language versions.

They test 18 brands in size 155/70 R13 and 16 in 205/55 R 16. The types are rated under 7 categories (performance on ice, snow, dry etc) with an overall score and the approx price.

84
Only a very rough g uide, but with Europcar Switzerland winter tyres were mandatory from 15/11/06 - 30/04/07 last winter.

85
Winter tyres are temperature specific and not snow specific... Hence when it drops below 3 or 4°C on a night you would be well advised to be driving with winter tyres on. Hence end of Oct/start of Nov until mid to end of March...

86
Changed mine this week, although I do spend a lot of time at weekends up the hill!

Come on the snow...

87
Thank you everyone for your good advice, we'll take a chance with chains this year and get down to the valley if needs must!

Ruddsyboy

88
Thats not what was posted earlier - see the comments re silicon and good summer tyres.

Not saying you are wrong as I don't know from anywhere but this thread but the earlier comments refute this and the graphs posted by the Aussie chapy - unless I misread them - prove it.

?

89
Sheesh. I believe this has already been proved many times - and not only by tyre manufacturers, but also independent parties. Yes there is silica (not silicon...) in summer tyres... but the compound is not the same. See the test I mentioned by Honda, and for the non believers, there are also among others tests carried out by the Canadian mounties in cooperation with US Army cold weather research centre ( believe this was at least 99 and 04 at least those Im aware of - testing of tyres for high speed pursuit ford vics) demonstrating behavior of winter versus all season tyres at acceleration, braking and on the skidpad.

If you still aren't convinced - try driving on winter tyres in summer, and see how much faster they wear. Then try to figure out why they wear out faster at higher temperatures...

90
I have told you how it is you can accept it or not. You could even go into a tyre shop and ask whether there is any difference. You could even go on all the manufacturers websites and check.

To Woodsie's graphs - Look at the temperatures... 20°C and 5°C. That's practically summer weather and still you can see the winter tyres performing at least on par with summer tyres at 5°C...

What I have said is when you get to low temperatures ie 0°C and below you are effectively being grossly negligent if you drive a car. IF you have an accident you will be treated that way too. So its your call and when you do get a 6 month driving ban don't try saying but woodsie's graphs said it was okay...

91
I think this will be my last post, as we don't seem to be getting much further.

Summer and winter tyres have two differences:

1) the thread pattern. Summer tyres are made to drain water, winter tyres to release anything trapped in the pattern. If you drive a summer tyres on snow, it retains the snow and are effectively slicks (I have thried this, not to be recommended). Winter tyres also have little lamellas, which increase grip in snow but give more noise and slightly less grip on dry road.

2) the rubber compund. This _is_ softer on winter tyres (I do not think I stated otherwise), but at moderate winter temperatures, on dry road this is to some dregree offset by differences in pattern. I have to add that I realise that my statement on -10 may be exaggerated.

But with the official Danish recommendation in mind, I would like to see:

Documentation for " In other words when the temperature falls below 0°C it is reckless to be on the street with summer tyres and if you get into an accident in these temperatues you will be dealt with accordingly..."

If there is nothing in the Swiss law about winter tyres, how can you be punished for not having them?

Documentation for " At -5°C on a dry road winter tyres will bring you to a halt in a third the distance of summer tyres like for like. "

I have driven summer tyres in the winter, and I think I would have noticed if the grip in dry conditions was that much poorer than in the summer. For example by making a close study of the countryside.

If I get the latter, I will retract my statement on summer tyres oin cold conditions (and we are talking recent brand-name tyres, ok?)

Safe driving to you all!

92
It is all out there on the internets, if you only cared to look... Whatever the official Danish recommendation is, physics remain pretty much constant. Cut a piece of your summer tyre, one of your winter tyre, put them in the freezer, see what happens. Maybe you haven't seen the countryside as you say. Just yet.

Alternatively , I can get into a multiple-variable Lagrangian equation system to give you a mathematical demonstration of what you require - i.e. a variable cannot be optimised across a whole range of another variable.

Once that is done , maybe we can get into more technical stuff like reverted rubber hydroplaning .

93
The law states that cars must be street safe and maintained, court rulings against drivers who caused accidents with inappropriate tires are based on this article. Once a court ruling is available, many insurances won't pay the entire damage.

The law isn't more elaborated because exact definitions of tyre types aren't available and might change in the future and might release drivers from their personal responsability if the weather doesn't follow the calendar. So the consensus is it should best be left to the personal responsability of the drivers.

This and an abstract of the whole situation can be found here in German.

94
I have cared to look, but I just cannot find the mention of 3 times longer braking distance on dry road. Can you help me?

BTW, I will probably get winter tyres - for going to the mountains.

95
Thank you. Do you know if courts have ruled summer tyres inappropriate on a dry road at -5?

The advantage of the German rules (snow/ice as indicator) is that the definition is easy.

96
Nathu raises a interesting point as so many drivers overlook the fact that they have a responsibility and while some circumstance may not be covered by a specific law they can nevertheless be charged with an offence. For example, as soon as there is an accident a driver will claim that they were within the speed limit and, while this may be the case, in the UK they can still be charged with Driving at a Dangerous Speed even if they were within the limit.

97
There you go: Honda study . The abstract covers wet distance braking, but dry distance is also covered within the study - more importantly, the relationship between compound and temperature.

I'm sure if asked nicely you can even get it for free if you do not have access to JST.

98

99
You are quite right that the German law is much clearer on this point. You can drive around all day with any tyres you like in Switzerland but if you have an accident then you could be in for some fun. Note here there is no case law so each case is individually dealt with by the judge in question and is always open to their interpretation of the law. It is also possible to appeal most things all the way to the supreme court it just costs money. I know of two cases where people have lost there license for causing an accident in very cold conditions. Effectively not been able to stop in time due to having summer tyres on. I would say though these are the exceptions and not the rule.

100
Ok guys,

say I'm sold on the idea that I should get winter tyre set for my car.

My car is a BMW 330d Touring, with all season runflats, 205/55/R17

BTW: I will be driving in switzerland a maxium of 3 weeks per year over winter period each year.

Advicee I've read so far, suggests best to try and get decent 2nd hand rims and get narrower ones for winter.

What would be most economical way to get winter set?

Not much of a market for winter tyres here in UK, and even less 2nd hand.

So I'm thinking I should try to find set in switzerland... ?

Any advice greatly appreciated!

Thanks.