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Car Forum / Mercedes-Benz Cars / December 2005Rubber compound in winter tyres
Something has been puzzling me a bit regarding winter tyres. It is said that one advantage of winter tyres is that the rubber compound stays softer at below about 7 deg C, giving better grip. So far, so clear. However, the tyre temperature rises after driving for a while, especially on motorways. So, where would the advantage of the winter compound be at this point? DAS For direct contact replace nospam with schmetterling --- Think of it in comparitive terms. Winter tyres use a compound that stays softer than your regular or all season tyres. So they grip better and will also give fewer miles out of a set of tyres than the other types. I think it would be fair to think that the tire's temperature will be affected to a considerable extend by the road (water, snow, etc) temperature All those 'sipes' in the tire will be full of water/snow, for example, and equilibriate the tires temperature tout suite to something certainly below the tire's temperature on a summer day. At least thaat's how I think about it cheers, guenter >Something has been puzzling me a bit regarding winter tyres. > [quoted text clipped - 12 lines] >For direct contact replace nospam with schmetterling >--- > Something has been puzzling me a bit regarding winter tyres. > [quoted text clipped - 12 lines] > For direct contact replace nospam with schmetterling > --- The advantage of the winter tyre compounds is, as you note, that they stay softer (and stickier) at low temperatures. Ordinary tyre compounds tend to get harder at low temps and are not as sticky. As you drive, all tyres will get softer to a degree due to heat caused by flexing, but the winter tyres have the advantage because they will still be softer and stickier since they start off that way. A good analogy is gliding. All planes can glide to some degree, but gliders -- with their wide wings and light weight -- glide longer. So regular tyres that are driven for a bit will stick better to snow than when they would from a cold standstill, but winter tyres with a special compound will be softer and stickier still because they are designed to be so. Thanks to the three of you for the comments. The thrust of your argument though is to imply that summer tyres should be made of a compound closer to that of winter tyres, even if without the deep tread. But summer tyres already are made of what the manufacturers think of as an 'optimised' compound balancing 'softness' with wear. I did not think that tyres gripped snow as such, but used the deep tread to 'squeeze' through the snow, just like normal tread disperses rain water. In southern England we rarely get snow and then it is usually a thin layer that melts quickly, especially in London. We do get slush occasionally, for which, of course, deep tread is useful. Tyre temperatures may well equilibrate at lower temperatures than in summer, but these must be above 7 deg C, at least when ambient is about zero or above. Or have I missed something? DAS For direct contact replace nospam with schmetterling --- [...] > As you drive, all tyres will get softer to a degree due to heat caused > by flexing, but the winter tyres have the advantage because they will [quoted text clipped - 6 lines] > compound will be softer and stickier still because they are designed to > be so. "The thrust of your argument though is to imply that summer tyres should be made of a compound closer to that of winter tyres, even if without the deep tread. But summer tyres already are made of what the manufacturers think of as an 'optimised' compound balancing 'softness' with wear. " Even among summer tires there can be considerable variation in the characteristics of the particular tires. It's not like there is one formulation for summer, one for winter and that's all there is to it. Look at charts of tire performance, and you will see that some summer tires are optimized for traction, which means they use a stickier formulation. Consequently, they don't last for as many miles. Other summer tires have less desirable traction characteristics, but will last much longer because they are made of a more durable, but less sticky compound. Winter tires are generally optomized for better traction, which means stickier. I'm not sure how much that would really help in snow, where the tread pattern is probably most important. But on wet or slick pavement, which also occurs in winter, the stickier tire will do better there. talking about snow vs summer tires in England is splitting hair..... I don't believe a summer tire would be any worse than a snow in 5 to 10C ... re snows, I think we are probably talking -20C .... maybe exagerating a tad cheers, guenter >Thanks to the three of you for the comments. > [quoted text clipped - 31 lines] >> compound will be softer and stickier still because they are designed to >> be so. Temperature is only one small part of equation. Summer tire has a different range of temperature. Not only it is higher and softer... it also must tolerate the extreme temperature at extreme speed... which snow tire cannot handle. The tread design is also different... by a wide margin. All the sipes, the tread design, and performance in extreme weather condition as you mentioned... snow to freezing rain to ice. That's why Nokian are the best... not only the Finnish has the similar weather condition... they experience all those condition in one single day. Aside from that, like all European, they demand performance too. |
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