22 replies to this topic

[kober]

There's now a debate in the Czech Republic about making snow/winter tyres compulsory. First idea about the law was to make it compulsory from a certain date to a certain date, but warm winter including +13 centigrades in January made it impossible. Then it started to snow finally this Tuesday and there's another idea - snow/winter tyres to be compulsory in snow/ice/slush conditions. But there's a lot of people opposing this using the "magical +7 centigrades formula" - that snow tires are more efficient on the dry/wet roads once the temperature is below +7 degrees celsius'. This is based on the tyre makers/sellers propaganda saying that softer compound gives more grip.
On the other hand from my subjective experience handling and grip of winter tires is much worse even in icing conditions. German automotive magazine AutoBild did a test, which stated that winter tyres only become better when the snow/ice/slush is on the road. Braking distance figures and handling test times are also considerably better in the dry/wet for the summer tyres - unfortunately the temperature during the test is not mentioned. Also ADAC tests which include all-year tyres show considerably better performance on the dry/wet roads for the all-years, despite their harder compound. But again - no temperature stated.
I believe that the advantage comes from the structure - snow tires tread is generally splitted into more blocks, which are subsequently splitted into those tiny zigzag patterns. I don't know whether softer compound means also more deformation of the sidewalls. On the other hand blocks on the summer tyres are more massive.
But is it really so? What is the ratio of those effects? Is there anything I haven't thought of? Is it just a propaganda or are tyre manufacturers right? Do you have any interesting data?
Disclaimer - I use winter tyres.

[imaginesix]

I am convinced that at the very least tire construction is very different between summer/winter tires after I left my summer tires on into late fall, and on cold mornings the tires could be felt to have a 'flat spot' where they sat overnight so the car would lump along on 4 bumpy tires until they warmed up. This never occurred with winter tires even at much colder temperatures.
Of course, the grip in snow/slush is far superior with the winter tires too. It surprised me that they even performed better through standing water, though they were skinnier and perhaps less worn at the time.
Anyways, you should be glad that you are able to have such a debate there. If anyone suggested making winter tires mandatory here they would be chastised, ridiculed, and perhaps even threatened into the sidelines.

[jcbc3]

I don't think you should make winter tires compulsory. As you say it is always hard to decide at what point exactly they should be put on. Another solution could be to allow the insurance companies to refuse cover, if you had an accident in winter/snowy conditions and it turned out you were wearing summer tires.

We have had the same weather in Denmark as you guys. So I have just be listening in on the weather report and when they said last week-end that snow would finally fall on MOnday, I just switched tires. A nice little Sunday chore.

[Ursus]

In Sweden we already have made wintertires compulsory. Though only during the period 1st Dec to 31st Mar but only during "winter road conditions", meaning when there is snow or ice on or next to the road. Insurance companies have latched on to this and does refuse cover should you drive with illegal tires.
Ofcourse it's not illegal tio drive with winter tires all year like some do...

[jcbc3]

I think we can agree that winter tires in the summer is still a lot safer than summer tires in the winter.

[kober]

My opinion on the topic of compulsory winter tyres is that I'm definitely against time-based obligation and partly against snow/slush/ice only obligation (German model). But I think it should be possible to severely penalize drivers who cause an accident on snow wearing summer tyres. I just need some good reasoning for it

[kober]

Originally posted by jcbc3
I think we can agree that winter tires in the summer is still a lot safer than summer tires in the winter.

No. For first thirty days of our winter they were at least on par. Now when there's half meter of snow you are certainly right, and yes, snow generally comes in winter. Or in spring. Or in autumn.

[jcbc3]

huh?

[GregorV]

This message is coming from someone living in a country where winter tyres were already made obligatory

There is two main diffrerences between the two types of tyres, one is of course the profile of the tyre with the winter tyres typically having more of wider, deeper cuts, but another important factor is the type of rubber used. Each sort of rubber has its own temperature window within which it works, with the summer tyre having a higher temperature operating window and the winter tyre the compound is softer and works better at lower temperatures. At too low a temperature the summer tyre will simply become too hard and as such lose a lot of its grip, as this depends a lot on the ability of rubber to absorb deformation energy.

The dry performance of either winter or summer tyres even in cold conditions isn't much of an issue. The first time the summer tyre starts losing out is in cold, wet conditions. In the dry, even if the road temperature is below the window required for the summer tyre, the tyre will nevertheless heat up and therefore work. In the wet, however, the cold water will quickly cool down the tyre so the summer tyre performance will deteriorate, but likely still not unsafely so. The effect, however, is of course even more apparent on snow where along with the cooling the summer tyre is also not properly cut to be able to dig into snow and then things become unsafe.

Making the winter tyre compulsory only on those days when there is snow on the roads would technically be more than enough. The problem, however, is that people simply do not abide by such laws, as changing all four wheels on a snowy morning when you're already late for work sounds much more inconvenient than the small probability of being stopped by the police and getting a fine. It then takes just a few ill equipped vehicles to cause accidents that completely block the road system, not to mention cost lives.

That said, global warming may soon make the issue obsolete indeed ;)

[kober]

Originally posted by jcbc3
huh?

Summer tyres on the snow are much more dangerous than winter tyres on dry/wet asphalt. Snow mostly appears in the winter. But it doesn't mean that summer tyres in the winter are much more dangerous than winter tyres during the summer.

[jcbc3]

Originally posted by kober

Summer tyres on the snow are much more dangerous than winter tyres on dry/wet asphalt. Snow mostly appears in the winter....

Which is exactly what I said

Originally posted by kober
...But it doesn't mean that summer tyres in the winter are much more dangerous than winter tyres during the summer.

Yes, they are.

[imaginesix]

Originally posted by jcbc3
Which is exactly what I said.

No, you said "summer tires in the winter" which is different from "summer tires in the snow".
It's the snow that compromises summer tire performance so much, not the change in seasons, and if you are considering drafting regulations that require winter tires (or snow tires) this distinction is critically important.

[Paolo]

Originally posted by kober
But there's a lot of people opposing this using the "magical +7 centigrades formula" - that snow tires are more efficient on the dry/wet roads once the temperature is below +7 degrees celsius'. This is based on the tyre makers/sellers propaganda saying that softer compound gives more grip.
On the other hand from my subjective experience handling and grip of winter tires is much worse even in icing conditions.

Soft compounds are OK on race tyres, but will not help any if mounted on a road tyre.
Race tyres have a thin layer of rubber.
Road tyres have a thick layer of rubber.

Thick layers of rubber have all sort of issues when temperature rises: they will start losing chunks, layers of rubber will slip over each other, there will be a lot of inside strain that will generate a lot of heat...
The softer the rubber, the worse these effects.

That is the reason why each time a race series has mandatory street tyres, teams shave them to any allowed limit

That is also the reason why, while actually being softer, winter tyres will make a car slower, not faster, in "dry autumn-spring" conditions . Deep thread makes things even worse.

[crono33]

i think the issue is quite complex

i come from south italy, but i have lived in sweden, ireland, switzerland

and i drive a clio williams.

"summer tires" (when new/not worn out) are IMHO overall much superior in any condition except snow/ice

on snow, studless winter tires are much, much better than summer ones. on ice they are much better than summer tires but grip is not great. studs are banned here.
on ice only studs work. even winter tires dont offer much grip, which is anyway much better than summer tires.

but winter tires vary a lot in quality of grip, and also tend to age (in my experience) quite quickly and then generate all sorts of issues.
for example, due to different rate of wear, i now have 2 different type of winter tires in my car, front and rear. they are from same manufacturer. rear ones have more thread, so they work better on snow. front ones are a intermediate tire. not too bad on snow but much better on dry/wet.

last year they worked quite well on dry and wet, worked decently on snow and somewhat sucked on ice
this year the rear tires work decently on snow (havent had ice yet) and dry but thet SUCK big time on wet, so that last week i almost swapped ends on a motorway ramp i negotiated at a rather low speed. grip at the rear is marginal to say the least. yank the wheel and u are sideways. dangerous.

now considering that i ride the tires only 3/4 months a year, the wear is very low. tthreadwise are almost new, rear tires are 2 years old and front 1 year old. but on the wet these rear tires are DANGEROUS and will have to throw them away. had this problem before

so what i have noticed is that winter tires need special attention. they age quickly and often u will have to dump them even though they look new.

i also saw macroscopic differences model to model and brand to brand

[crashout]

Hello All.

I have driven lightweight compact (North American Festiva, Tercel, Corolla, Accord, Probe, CRV: maybe considered larger in Europe) cars (and motorcycles) in the near north of Ontario Canada for 20+ years. At the edge of the Great Lakes, we get a pile of snow (called "lake effect snow") almost daily in winter anywhere within 50-100 km of the lakes edge almost immediatealy after a wind turn.

I swithched to 4 wheel full snow tires almost as soon as I started to have to drive almost 220km weekly from Muskoka to Owen Sound ON Canada. My drifting skills became instinctual. Half the time I felt like I was driving a skidoo.

My 12"x145mm tires had thin highly deflecting sidewalls and an agressive deep bloc tread pattern.

In the dry they weren't bad with normal (35lb ish) pressures when warmed up.

Either way a 2000lb car was not stressing these, and was a blast to drive on top of the snow.

Happy slappy

AT

[The Kanisteri]

Originally posted by Ursus
In Sweden we already have made wintertires compulsory. Though only during the period 1st Dec to 31st Mar but only during "winter road conditions", meaning when there is snow or ice on or next to the road. Insurance companies have latched on to this and does refuse cover should you drive with illegal tires.
Ofcourse it's not illegal tio drive with winter tires all year like some do...

Nothing wrong to use winter friction tires during summer, though they are not evel close good enough than summer tires on dry, warm asphalt

But I agree there are idiots who drives with studded tires till June...

[jokuvaan]

Nothing wrong to use winter friction tires during summer

Except hot summer day and fair speed will wear them down.
In Swedish/Finnish car magazines there is every year comprehensive tests between friction, studs and so on. One thing tested was used friction tyres in summer, one word: dangerous, particularly on wet.

[crono33]

forgot to mention that tire size makes a huge difference on snow/ice

narrow tires work much much better.

[McGuire]

Due to the nice sharp edges in their tread, brand new fair-weather tires will have significantly better grip in the snow for the first few thousand miles.

But running winter tires all summer long will diminish their bad-weather capabilities considerably, due to the accelerated wear and heat cycles.

[McGuire]

Originally posted by crashout
I swithched to 4 wheel full snow tires almost as soon as I started to have to drive almost 220km weekly from Muskoka to Owen Sound ON Canada. My drifting skills became instinctual. Half the time I felt like I was driving a skidoo.

Can you have more fun driving a car? I feel sorry for folks who never get to drive in snow. I can't imagine how one learns car control without it, must be difficult.

[Greg Locock]

Gravel roads

[Engineguy]

Nick prefers spiked Bridgestones for winter driving. GO COLTS!

As usual though, the prancing horses in red livery were faster.


(photos today at the 100th anniversary White Turf on the frozen lake of St. Moritz)

[phantom II]

So typical. The cheat team will stop at nothing to win. Everybody else has 2 wheel drive.

[QUOTE]Originally posted by Engineguy

As usual though, the prancing horses in red livery were faster.