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Chris - so these weren't just tyres, they were M&S tyres .....?!
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Very good I like that.
On a serious note winter tyres with under 4mm of tread are illegal in Germany and we have no choice about changing October to March is winter tyre time.
www.atu.de/pages/home.html
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Great discussion. I love tyres!
Below is a pdf of an October 2007 test of 10 winter tyres against the best all season tyre carried out by Auto Bild of Germany.
tinyurl.com/3xhz9m
(I use Google language tools and Altavista Babelfish to translate but the results are not very good. However, the tables and charts speak for themselves.)
These tests involve key performance measures in snow, wet and dry. Included are noise tests at 2 speeds and rolling resistance. They also compare a summer tyre in the wet and dry tests. The key data missing is the temperature at which the wet and dry tests were carried out. The summer tyre is significantly better than the others in wet and dry braking. Yet we all read how winter tyres have better grip below +7 degrees.
Here is another Auto Bild article on winter tyres (html).
tinyurl.com/2om5oo
Modern winter tyres are significantly improved on even 5-year old designs. There is really no comparison between a modern winter tyre and a 1970's M+S tyre as might have been fitted on a Land Rover Series III !
Further useful reading are the Winter Tire Tech articles on the American tirerack.com
Here are the Transport Canada Winter Tire Safety Tips
www.tc.gc.ca/roadsafety/tires/wintertires/menu.htm
I would guess a winter tyre with 2 mm of tread would be WORSE in snow than a summer tyre with 6 mm of tread. Both of them will be horrible! I second the view (having driven in 3 nordic winters) that once you get down to 4mm on a winter tyre you should just keep it on for the summer.
My half worn M+S Goodyear Wranglers (OE) are very noticeably more slippery compared to my new Yokohama Geolandar I/T+ winter ice traction. The Yokohamas are 40mm narrower which significantly contributes to their snow and slush performance. From walking pace the Yokohamas will stop my 4x4 easily on the steep ice encrusted slope of my driveway, the Goodyears won?t. It is truly amazing to see.
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Thanks for that, Billy Whizz. Excellent and very interesting. Alas, I know no German, but the charts are very revealing.
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Included are noise tests at 2 speeds and rolling resistance. They also compare a summer tyre in the wet and dry tests. The key data missing is the temperature at which the wet and dry tests were carried out. The summer tyre is significantly better than the others in wet and dry braking. Yet we all read how winter tyres have better grip below +7 degrees.
That really is astonishing. Not to tell us the temperature at which those tests were carried out really means that they are pretty pointless. If those tests were carried out at, say 10 or 15 degrees, then that is what we would expect. If they were carried out at 5 degrees, then that puts a different slant on things.
The other thing that surprised me is that, if I understand the graphs, winter tyres are considerably better than summer tyres for rolling resistance. I'd never heard that before.
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My thoughts exactly, tyro!
I find the Auto Bild test to be very frustrating reading because I am still trying to justify getting an extra set of tyres for winter use in the SE UK ! Also note the details of summer tyre are not once specified in the article. Plus, judging from the number plates, the snow tests were carried out in Japan (last winter?) and all the others in Germany (it doesn't look too wintery in the photos).
My conclusion from the Auto Bild data is:
[1] the performance on snow of a summer tyre compared to the winter and all season tyres is shockingly bad. E.g. "Braking on snow from 50 kph: the AUDI stops on the Vredestein after 28 meters, the all season Goodyear needs an additional car length. The summer tyre continues to slip for another 33 meters."
[2] However, in every single safety test on wet and dry roadways the summer tyre was superior although sometimes not by much. "Aquaplaning: as expected the summer tyre has the least problems, upto 93 km/h keeps the tyre in contact with the roadway. With the winter tires only the Vredestein offers similar security reserves, the Sportiva already aquaplanes above 75 km/h." "Braking in dry from 100 kph: Against the summer the winter tire does not have a chance with a full brake. Already with the all season tyre the braking distance extends by one and a half vehicle lengths." (Summer tyre 39.5m, Goodyear 45.9m). All the other winter tyres are worse.
[3] in the noise test, the summer tyre was within 2% of the winner. Most winter tyres are not significantly noisier than summer ones.
[4] as you say, surprisingly, the summer tyre had the largest rolling resistance on test. "A five percent lower rolling resistance reduces fuel consumption by one percent. Then the Michelin Primacy Alpine saves seven percent fuel compared with the summer tyres."
Does anyone have any other tests between summer and winter tyres?
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