2 or 4 Winter Tyres

vaio

liquidbutindebt wrote: »

........While insurance companies do not need to be informed about winter tyres all round, if you decided to put just 2 on I think you would probably be in a lot of trouble if you had to claim.........

I can certainly see an argument that mixing summers & winters could be regarded as affecting roadworthyness (given that winters/summers in the snow is more of an imbalance than radial/cross-ply) and of course if that caused or contributed to the accident then they could decline the claim.

Having said that, given the general knowledge about winters I can't see it happening unless the police had prosecuted which I think would require change in the law to bring summer/winter mix in line with radial/crossply. If lots of people start fitting two winters and having oversteering accidents then might see some change to the law

susank

I am confused by the bad feeling in this thread having read most of it - can I ask where you all are when you are driving in such snow - where I live 20 inches last week is the norm in bad winters up here - we are used to it and we have always and repeat always been advised to put the new snow tyres on the driving wheels so on front wheel drive new snow tyres - I run toyos which can be run all year anyway as are good for the rain grip and have never never had a problem with my Yaris - I have driven in snow in many different cars for 40 years and never had a problem. The insurance co does not need to know about tyres provided you dont run slicks!

mikey72

liquidbutindebt wrote: »

Newton's second law. And it's not about locking, it's about friction differentials.

So, not much to do with the acceleration of an object being dependent on the net force acting upon the object and the mass of the object then.

liquidbutindebt

vaio wrote: »

I can certainly see an argument that mixing summers & winters could be regarded as affecting roadworthyness (given that winters/summers in the snow is more of an imbalance than radial/cross-ply) and of course if that caused or contributed to the accident then they could decline the claim.

Having said that, given the general knowledge about winters I can't see it happening unless the police had prosecuted which I think would require change in the law to bring summer/winter mix in line with radial/crossply. If lots of people start fitting two winters and having oversteering accidents then might see some change to the law

Frankly, an insurance company will do anything to wriggle out of a claim. Defending the fact that you deliberately altered the handling of your car in court, against the advice of tyre manufactures and against the insurance company that refuses to pay out... well that's not somewhere I'd want be.

I think it's more complex that this. I can give a simple example that has been stated elsewhere. You drive a FWD car fitted with winters on the front only. You are driving along a residential street, with cars parked on both sides. Someone pulls out from a side road, or from the side of the road (previously parked). You slam on the anchors. You lose control and spin. You whack a parked car, lamp post, pedestrian on pavement. Guy that pulled out continues on blissfully unaware. Ordinarily, that's his fault or at least a 50/50 claim because ordinarily, you would've only hit him. Now, purely because of your tyre choice you have a 100% fault claim to deal with.

All of these people who post saying it's never been a problem... well the issue is, until you have to claim on your insurance you are never going to know whether it's a problem or not!

liquidbutindebt

mikey72 wrote: »

So, not much to do with the acceleration of an object being dependent on the net force acting upon the object and the mass of the object then.

Net force includes friction! What are you trying to say?

mikey72

liquidbutindebt wrote: »

Net force includes friction! What are you trying to say?

So if you don't change the tyres, there is no change in force then, You haven't changed any mass, so the back tyres must behave in exactly the same way regardless.
If you drive as if you are on a dry summers road, yes, you'll have problems. If you drive as if you're on snow and ice, it'll be an improvement on four summer tyres.

liquidbutindebt

mikey72 wrote: »

So if you don't change the tyres, there is no change in force then, You haven't changed any mass, so the back tyres must behave in exactly the same way regardless.
If you drive as if you are on a dry summers road, yes, you'll have problems. If you drive as if you're on snow and ice, it'll be an improvement on four summer tyres.

Did you account for the increased forward mass transferral as a result of increased traction at the front? I don't think you did. Schoolboy error I'm afraid.

mikey72

liquidbutindebt wrote: »

Did you account for the increased forward mass transferral as a result of increased traction at the front? I don't think you did. Schoolboy error I'm afraid.

What????
Forward mass transferral because of increased traction????
Apart from that being gobbledygook, according to your law of physics you're supposed to be spinning or now going backwards anyway.

liquidbutindebt

mikey72 wrote: »

What????
Forward mass transferral because of increased traction????
Apart from that being gobbledygook, according to your law of physics you're supposed to be spinning or now going backwards anyway.

Not at all. The act of braking (a deceleration) results in transfer of mass to the front of the car. That's why it's the front brakes that do 90% of the braking and also why your front suspension dips when you brake. So, what you have with winters on the front is excellent grip and greater friction than on summer tyres. You also have far more forward mass transfer than if you were using all season tyres and, as a result, the rears have far less mass (and far less friction) over them than if you were using a matched set of summer tyres. With a full set of summers there is reduced deceleration and reduced forward mass transfer.

For a better explanation of this phenomenon look here: http://en.wikipedia.org/wiki/Weight_transfer

mikey72

I'm quitting now, I suggest you do indeed use 4 matching tyres.
(If you want to google tribology and Amontons' Laws of Friction, but give up on Newton)