Autocar: Winter Tyres

[John Jones Jr]

Just how good are winter tyres? | Autocar

 

[Spinal]

Watch out...

 

[st13phil]

^ Ha ha ha

 

[Rory]

I'm putting All-Seasons on mine. On the back only.

 

[wemorgan]

I'm grateful that so many are putting their winter tyres on in October. Because of it, today the temperature has been 16C in the Midlands

 

[grober]

I think that's what's termed a resounding endorsement complete fail on the weight transfer issue on the acceleration test of course :fail and a re-iteration of the still widely held fallacy based on the old winter tyre tread compound technology of the mid 90's
Winter tyres FAQs
Can I drive on winter tyres in summer?
Yes, but the best thing to do is store them in the summer otherwise they’ll wear out quite quickly.

--- Er no they won't --- at least no faster than any summer tyre in the UK's predominantly temperate climate.

 

[BTB 500]

OK I'll bite

There were some other qualities about the car on winter tyres that were less desirable, true.
...
And the car’s traction control also become neurotic, killing the power at the merest whiff of throttle, even on bone dry roads.

That confirms a significant reduction in grip when it's not snowy/icy (presumably "even" on dry roads means it also happened when they were wet). The winter tyre test last year where braking distances were objectively measured found the same thing.

So in summary ... they are a great convenience in that you won't get stuck if it snows. But from a safety POV they are worse than standard tyres when there isn't snow/ice, and of course traffic speeds are higher. IMO they are a no-brainer if you live in an area where there's consistent snow in winter (Germany etc.), but that doesn't apply to much (most?) of the UK.

 

[wemorgan]

. But from a safety POV they are worse than standard tyres when there isn't snow/ice, and of course traffic speeds are higher.

In my mind cars that cause accidents are:

cars in summer, on summer tyres driving too fast
cars in summer, on winter tyres driving too fast
cars in winter, on summer tyres driving too fast
cars in winter, on winter tyres driving too fast

The idea that it's cars in summer on winter tyres causing accidents is not looking at the whole picture IMHO.

If you remove the 'driving too fast' aspect and assume a sensible speed in all weather conditions then you'll mostly be safe. Winter tyres in winter off that extra level of ability some motorists value. Any reduction in their summer performance is offset by the motorists ability to drive at a sensible speed.

 

[Rory]

...But from a safety POV they are worse than standard tyres when there isn't snow/ice,

My problem with this argument is that it's too much of a generalisation.

Used in summer, some winter tyres are probably better than some summer tyres.

It's the same reason you get people saying they've never had any problem driving their MB in winter, when other people can't move on the slightest incline - in winter, some summer tyres perform better than others.

 

[Sp!ke]

I thought the article raised a few questions.

It sounds like BMW dropped a ball and changed the rolling radius of the wheels significantly - this smaller radius and therefore gearing would probably explain why it was easier to bring on the traction control light as opposed to being caused by lack of grip which was more than dismissed earlier in the article.

at BMW’s insistence the car was fitted with a set of Michelin Alpin winter tyres. And when it came back I was stunned by how different it felt to drive; how much more comfortably it rode, how much sweeter it steered, how less fidgety it felt on badly surfaced roads, and how much more grip it had everywhere in the wet.

The whole car felt as if it had been unlocked somehow, and there was also an amusing little sticker that had appeared in the top right-hand side of the windscreen, warning me not to drive above 149mph. As if BMW GB was saying: ‘Because we know what sort of larks you normally get up to in our 1M…’

There were some other qualities about the car on winter tyres that were less desirable, true. I noticed, for instance, that the speedo had become wildly ambitious; at a true 70mph it was reading almost 80mph, which meant the fuel range indicator was similarly off-piste. And the car’s traction control also become neurotic, killing the power at the merest whiff of throttle, even on bone dry roads.

 

[grober]

OK I'll bite

And the car’s traction control also became neurotic, killing the power at the merest whiff of throttle, even on bone dry roads
That confirms a significant reduction in grip when it's not snowy/icy (presumably "even" on dry roads means it also happened when they were wet). The winter tyre test last year where braking distances were objectively measured found the same thing.
So in summary ... they are a great convenience in that you won't get stuck if it snows. But from a safety POV they are worse than standard tyres when there isn't snow/ice, and of course traffic speeds are higher. IMO they are a no-brainer if you live in an area where there's consistent snow in winter (Germany etc.), but that doesn't apply to much (most?) of the UK.

I would beg to differ slightly in that you are assuming the traction control kicking in signifies a big reduction in grip whereas what in fact is being measured is a significant variation in tyre rotational speed due to the greater flexibility of the deeper tyre tread. In addition accelerometer sensors may also translate great vehicle side to side movement as skidding when in fact that's not happening Since the absolute parameter measured by the traction control is not "grip" but rotational speed variation and accelerometer sensors measure sideways acceleration not degree of movement it possible that the traction control unit was triggered due operating out with its design parameters rather than due to absolute "loss " of grip. In other words send the traction control unit the wrong type of message and it may jump to wrong conclusion. I think this is borne out with the sentence "the car’s traction control also became neurotic, killing the power at the merest whiff of throttle, even on bone dry roads"
Its certainly true any car on winter tyres will "move about" more on the road under conditions of braking or cornering but that does not necessary extrapolate to loss of control or grip as flagged by the stability control unit in this instance . This tread movement would explain the reduced braking performance of the winter tyre in the dry which IRRC amounted to about a metre difference. This in comparison to the winter tyre advantage in the snow which amounted to something like 25 metres difference.
but as always we will have to agree to differ.

PS Must agree though that driving a car with winter tyres on which constantly triggered its traction control due to over sensitive operating parameters would be bloody annoying.

 

[Rory]

I would beg to differ slightly in that you are assuming the traction control kicking in signifies a big reduction in grip whereas what in fact is being measured is a significant variation in tyre rotational speed due to the greater flexibility of the deeper tyre tread.

I can't believe the tyres make that much difference - we run Michelin Alpins year round on one of our cars and they look and feel pretty similar to wummer tyres.

The BMW1M is no doubt a handful at the best of times, so perhaps the slightest things trips it over the edge?

 

[Spinal]

Right, I'll bite as well...

The article is a perfect example of opinion based reporting, and is a pile of tosh.

Winter tyres on the other hand, I swear by - and have already put them on my main car. Currently trying to decide if to put them on the smart...

M.

 

[V12]

I thought the article raised a few questions.

It sounds like BMW dropped a ball and changed the rolling radius of the wheels significantly - this smaller radius and therefore gearing would probably explain why it was easier to bring on the traction control light as opposed to being caused by lack of grip which was more than dismissed earlier in the article.

Isn't that one vehicle that has different size rolling radius front and rear like the chrysler cross fire?

He says it became much more comfortable despite a smaller rolling radius? Interesting, what tyre pressure difference was there?

 

[edstrom76]

It's the same reason you get people saying they've never had any problem driving their MB in winter, when other people can't move on the slightest incline - in winter, some summer tyres perform better than others.

It's also true that people generalise about 'winter'. I'm going to stick my neck out and say that people who say they've never had any problems driving their MB in winter are the same folk who have never actually driven in snow.

Nobody on the continent in their right mind would contemplate driving on summer tyres so why are we so different? Appreciate that some can't be ****d for the sake of a few days of snow/year and that's of course fine so long as they find other means of transport during those periods, however far too many people out there still chance it.

 

[DSM10000]

It's also true that people generalise about 'winter'. I'm going to stick my neck out and say that people who say they've never had any problems driving their MB in winter are the same folk who have never actually driven in snow.

Another generalisation?

Also quite inaccurate as I have driven my C320 in heavy snow in and around the New Forest and local roads here that had not been treated. I have never lost control or had a problem but in all cases I drove very carefully and slowly but I got home each time.

I have also driven in similar conditions in a Saab 9-5 Griffin, the MB has 205 section Michelin Primacy tyres fitted all around and the Saab had 215 section Hankook Ventus tyres so both relatively narrow and in the case of the Saab a heavy V6 engine sitting transversely over the driven wheels. It is as much about the driver as the equipment.

 

[BTB 500]

Tyres do vary - at least now you can look at the wet grip/braking performance on the label. They are rated from A (best) to F (worst), with the difference being almost 60' in braking distance (let's say four car lengths) from just 50 mph.

Look up the rating for your winter tyres, and compare with your summer tyres.

I would suggest that in most of the UK wet grip is more important from a safety (rather than convenience) POV than grip on snow/ice.

But as I said before if you live somewhere where there's prolonged snow then you certainly want winter tyres.

 

[grober]

A wee bit more on the EU label for tyres testing according to Michelin.

How to measure braking on wet roads?
This test is done with a vehicle under standardised conditions defined by law: namely, temperature, state of road surface, water depth, and speed.

The conditions of the tests, according to European legislation, are:

Winter tyres tested between 2° and 20°C
Summer tyres tested between 5° and 35°C
Water depth between 0.5 and 1.5 mm
Braking performed on 4 tyres with ABS between 80 and 20 km/h (approx. between 50 and 12 mph)

Which you could argue gives the manufacturers fairly wide wriggle room and if car manufacturers model emissions tests are anything to go by means testing at the temperature which will yield the most favourable results for their product.
Michelin evidently test as follows:-
" We have chosen to perform tests under conditions that are as close as to true European, driving conditions. This means Michelin will conduct all of its braking tests on wet roads at the most representative temperatures for typical European usage of its products.
Approximately 20°C for passenger car tyres
Approximately 7°C for passenger car and van winter tyres
Between 7°C and 25°C truck tyres (generally used in summer and winter conditions)
Since it isn’t possible to test every tyre in the market in identical conditions, all tests are carried out beside a “reference” tyre. In this way, the grade awarded to each tyre is always tested under the same conditions---- within the same test parameters.


However it does pose the interesting question of what sort of wet road braking figure would the summer and winter tyres produce at other temperatures. Perhaps a more meaningful comparison would be to test both at the same temperature. The annual average temperature for England 1981-2010 being around 9.6 degrees C.
Met Office: Rainfall, sunshine and temperature time-series
So to make a meaningful performance rating on wet weather braking in the UK perhaps both tyres might give more representative comparison figures if they were both tested at 9-10 degrees. The results might be interesting!


the regs!! EUR-Lex - 32011R0228 - EN

 

[Sp!ke]

That is very revealing as it makes official braking distance comparisons between summer and winter tyres a mockery.

 

[edstrom76]

Another generalisation?

Also quite inaccurate as I have driven my C320 in heavy snow in and around the New Forest and local roads here that had not been treated. I have never lost control or had a problem but in all cases I drove very carefully and slowly but I got home each time

Honestly, if your car had been fitted with tyres appropriate for the weather, you wouldn't even have reflected on the fact that you were driving in heavy snow and you wouldn't have had to creep through it. We are many many years from fully adapting to colder winters though, I fear.