Snow chains/winter tyres

[Muswell]

Didn't you look at the video that was on the link?

[Billggski]

There is a well known psychological condition called "cognitive dissonance", which explains how if someone has made their mind up about something, then evidence to the contrary actually reinforces their intitial, erroneous, view. The standard response is to rubbish the evidence, especially if it is from an "expert" on the subject.

i. e. someone who has actually researched the evidence available.

??

[Brian Kirby]

"Apart from the very dubious input by the tyre man, we are still at the point where I am advised to put my best tyres on the axle which will do the least good, because the publicity department of the man who wants to sell me more tyres says it may be safer. I recommend that each of you do the thing that you believe is right, but be cautious in choosing your experts and try to verify what they tell you before you make your mind up. Make sure that they are answering the question you asked, not trying to confuse you with spin."

 

The answer is simple. The advice given is given on the basis that it is the safest advice to give to drivers in general. It take no account of experience or ability, it is simply what observation under controlled conditions tells the observers works best for most people most of the time. There is no place for "belief" in this, "belief" is what folk have to resort to in the absence of factual information. If you consider that you have sufficient experience and ability to ignore the advice, fine. However, please don't rubbish the advice, because it is factually based. I would only ask how many of the contributors to this string have, actually, driven a fully laden motorhome on rutted, compacted, snow or ice, on summer tyres, with no chains? I can assure you from personal experience that it can be a quite "interesting" learning experience.

[starvin marvin]

Brian Kirby - 2016-08-21 1:42 PM

 

I would only ask how many of the contributors to this string have, actually, driven a fully laden motorhome on rutted, compacted, snow or ice, on summer tyres, with no chains? I can assure you from personal experience that it can be a quite "interesting" learning experience.

 

You may certainly ask, and the answer is quite a few times. I can also assure you that I can recall with some clarity driving up to the Spanish border with France, in January heading for Perpignan, behind a Spanish snow plough, and heavily loaded. At the border, not surprisingly he turned off the road which left us to sledge down into France, very much a white knuckle ride, and squeaky bum time/change of underwear. Should have waited at the col, as halfway down a French snow plough was on the way up!

 

Lots of ice on the roads as soon as you turned off the main roads. This continued for a long way north, more character building than a learning experience, in an old rwd Merc, shod with Michelin camping tyres, and no chains.

 

When I was working I regularly managed to get through a set of tyres annually, driving at least 50k miles, you learn to drive according to the conditions, a couple of mill difference in tread depth between tyres on front and rear axles in my view (with at least 50 years experience) does not make a blind bit of difference.

 

 

[Brian Kirby]

starvin marvin - 2016-08-21 7:07 PM.............................When I was working I regularly managed to get through a set of tyres annually, driving at least 50k miles, you learn to drive according to the conditions, a couple of mill difference in tread depth between tyres on front and rear axles in my view (with at least 50 years experience) does not make a blind bit of difference.

I think the issue of where to have the best tyres is different to driving on compacted snow/ice. If on compacted snow/ice, tread depth is of little to no significance for how much grip the tyres will generate, though it may have some relevance on uncompacted snow or mud. However, the difference between the tread depth on new tyres and those already on the vehicle can easily exceed 2mm. A new van tyre will have about 10mm tread depth, whereas the legal limit is 3mm. So, the tread depth difference between a part worn, but still legal, van tyre, and a new van tyre, could easily be 6mm, and I would expect the new tyres to deliver better adhesion on a wet road (especially with standing water) than the part worn ones.

 

Whether the new tyres should be fitted to the front wheels or the rear is based on tests carried out in a variety of conditions involving a variety of drivers. The outcome was that the new tyres provide the best grip under most conditions, and that most drivers (and cars) are safer with loss of adhesion at the front (understeer) than with loss of adhesion at the rear (oversteer). Where one actually puts the best tyres depends largely on how confident one is about controlling rear end breakaway, as opposed to front end breakaway. One might think that retaining steering control would assist if the rear steps out but, apparently, most drivers over corrected for the tail slide and executed a 360 (or thereabouts :-)) instead of regaining control. So, the old advice to fit the best tyres to the front was reversed.

 

I'm not advocating either approach, and what I do is for me to know, but I was suitably impressed by my experience one April on exiting the Grenztunnel (near Fussen) between Germany and Austria, from cleared roads in Germany onto full width rutted, compacted, wet, icy snow in Austria, on Michelin camping tyres, no chains (probably not usable if I had had them, though ice skates might have been!) with a fully laden 3.5 tonne FWD motorhome. We eventually took local advice and turned back until the Austrians had cleared the road, but it was already abundantly clear from the resulting mix mainly static and otherwise slithering light traffic and jack knifed and ditched HGVs that no-one was going anywhere in a hurry. Trying to keep the van on the straight and narrow under those conditions, with the front and rear wheels following whichever rut took their fancy, and frequently following different ruts at the same time, left quite an impression on me! So did the three (? :-)) point turn I had to execute to turn back. That really was interesting, and I don't think winter tyres would have made much difference either. Fortunately, the road was basically flat, and not too heavily cambered, so the periodic slides could just be restrained (controlled would be too strong a word), but I could easily understand how the 40 tonners ended up in the ditch. Once that much weight is travelling sideways on wet ice, it takes a looooooooooooooooooooong time (or a ditch!) to stop! :-D

[Archiesgrandad]

Brian I'm not trying to rubbish the evidence of the experts, I'm suggesting that we should be entitled to be given verifiable evidence of why we should do something so counter intuitive. Nothing I have ever done in the course of driving a range of middleweight commercial vehicles in all kinds of weather and road conditions has left me worrying about the backend breaking away, and my path has never been strewn with such vehicles being driven by others that have done so.

The bit of film is not too convincing, and does not look like a film of a major research program run by a major international manufacturer. The choice of tyres specified by the vehicle manufacturers is almost entirely driven by price, and occasionally availability will come into it. If they think that you will pay extra for something that is easy to fit they charge a premium for it.

It is obvious that some people will be better at driving on slippery surfaces than others, some of us can, if needed,drive for 12 or 14 hours a day, for day after day, others will be happier to restrict themselves to less. Some of our vehicles will cope better with winter conditions than others, traction control and other such equipment makes a huge difference, but for the life of me I cannot see how enhancing the grip of the front wheels will render a fully loaded medium sized van unstable and likely to slide sideways. Does it somehow make a mature, experienced driver suddenly go mad because he thinks he has a bit more grip under his front wheels, causing him to drive a unreasonable speeds and throw his vehicle from side to side? Perhaps the improved grip of these more expensive tyres is able to overcome the poor traction and turn in of the standard tyres and suspect design of the suspension, requiring us to relearn our way of driving these substandard vehicles, which would be a more attractive proposition for the manufacturers.

I'm not saying they are wrong, but for the life of me I can't see how they can be right.

AGD

[Steve928]

Over the past 20 years or so oversteer has been deliberately and comprehensively engineered out of today's vehicles. The industry feels that progressive understeer is the safest way for a vehicle to handle so that when numpty goes into a corner too fast for the conditons, all that numpty has to do is wind on more and more lock and in most situations the end result will be happy, certainly far happier than if numpty were confronted with a proper tail-happy slide, the like of which drivers of old used to encounter relatively frequently (and provoke deliberately for fun..).

 

I see this 'best tyres on the rear' advice as nothing more than the logical extension of that trend towards guaranteed understeer at all times.

 

As a non-numpty driver I don't feel that it's right for me. The most dangerous road conditon that I seem to encounter these days is standing water, down to increasing extreme weather conditons and decreasing maintenance of road drainage. For these incidents, usually in straight line, then it's 'best tyres up front' for me please.

[stvekay]

kevina - 2016-08-20 4:28 PM

 

Archiesgrandad - 2016-08-20 12:24 PM

 

I'm intrigued, if it is considered safe and appropriate to fit snow chains to the front wheels of an. FWD motorhome in order to improve traction, leaving the rear wheels to drag along behind in their own special way, why is it dangerous to fit special tyres to the front wheels of an FWD motorhome in order to improve traction, leaving the rear wheels to drag along behind in their own special way.

I can understand that if I was in the business of selling tyres I would tell everyone that you should only ever fit new tyres to all 4 wheels, and I'd try to think up some plausible justification.

AGD

Because with chains on you drive at about 20mph max so there is little lateral force on the rear wheels when cornering. The lateral force will have a square law relationship with velocity so at double the speed you will have 4x the lateral force making a rear wheel breakaway much more likely.

 

I spend 2 months every winter in the Alps in the van. At some time you must have driven on snow and experience how easily the back can slide out, with mis matched tyres this will be more likely to happen. The recommendation is, not only to have matching tyres all round, but also to have the tyres with the most tread on the rear.

 

ps Plenty more videos like this

That is with a car with probably 55-60% weight on the front.

 

So if you drive at 20mph with winter tyres on front should be OK? ie is front wheel drive.