2 or 4 Winter Tyres

C_Crawford

Pew_Pew_Pew_Lasers! wrote: »

ABS keeps the wheels from locking under braking, it does nothing to prevent a loss of traction, and also does nothing when that traction is lost to help you regain control. You're thinking of full traction control systems (not usually found on your average family saloon) but even still its much safer to use the correct tyre compound on each axle than to rely on a computer to get you out of trouble.

Do you realise what you have just said??
ABS Keeps the wheels from locking under braking...It does nothing to prevent loss off traction, em I'm confused now :-)
I thought that's why ABS was invented to stop loss of traction in emergency braking situations. Like preventing a skid by undulating the braking pressure thus regaining traction.
Correct me if I am wrong. Anyone else care to comment on this?

vaio

Think he's talking about loss of sideways traction to resist sideways forces like slightly off straight braking or cornering forces which ABS will do nothing to help with.

Scrounger

I agree with C Crawford.

IMO ABS will help prevent the rear wheels slipping sideways in slippery conditions (because the wheel is still rotating it will try to continue straight ahead rather than go sideways).

I've put two snow tyres on the front of my Focus - no problems. :beer:

Scounger

mikey72

vaio wrote: »

Think he's talking about loss of sideways traction to resist sideways forces like slightly off straight braking or cornering forces which ABS will do nothing to help with.

How will that be different if you don't change the tyres though?
If the conditions were going to make the back slide, they will still slide. If they weren't going to, having better grip at the front won't make it any worse at the back.

Pew_Pew_Pew_Lasers!

C_Crawford wrote: »

Do you realise what you have just said??
ABS Keeps the wheels from locking under braking...It does nothing to prevent loss off traction, em I'm confused now :-)
I thought that's why ABS was invented to stop loss of traction in emergency braking situations. Like preventing a skid by undulating the braking pressure thus regaining traction.
Correct me if I am wrong. Anyone else care to comment on this?

ABS was invented to stop wheels from locking under heavy braking, so that steering would (in theory) still be possible. You don't seem to understand what ABS does, what locked wheels are doing, and what traction means.

Think about it. You're braking in a straight line. The front tyres have plenty of grip so don't lock up. The rear tyres don't have as much grip, and the back of the vehicle swings out. All four wheels are still turning, but you realise there's a problem so brake harder. The front wheels are now being controlled by the ABS, but so are the back wheels.

How does ABS bring the vehicle back into line? All it does is modulate brake pressure, nothing more. To bring the car back into line you either have to apply opposite lock and power, or you need the help of an advanced traction control system to slow the car by braking each wheel individually, where appropriate.

It doesn't matter how advanced your brakes are, if your tyres are physically incapable of maintaining grip on the road surface, they will slide across it. Its simple physics. One day, if you're unlucky, you'll find this out for yourself.

liquidbutindebt

If you do decide to put 2 on the front, make sure you put slicks on the rear for maximum effect :mad:

Wow, there's some really scary misinformation going on here. ABS absolutely will not help in snow. In fact, ABS is far _less_ effective under those conditions than normal braking systems. The reason is quite simple. Snow is a non solid surface. When the wheels are locked, it builds up in front of the tyre and assists by providing increased friction and more stopping power. ABS prevents the wheels from locking and so this effect will never occur. The supposed benefit of ABS is that it allows you to apply braking force while also turning (the car will not turn with locked wheels), but again, in snow and ice, there is so little friction available that you basically have two choices. Turn a bit and don't brake or brake and don't turn, this is not really any different under ABS or normal braking.

As for using 2 or 4! You would be absolutely bonkers to run with just 2. While you may get away with it, you can never be sure, and kids do run out in front of cars sometimes. Remember, in winter conditions, far more accidents happen because people couldn't stop rather than couldn't get going! But the biggest issues with a FWD car and winter tyres on the front is that you never really know how much traction you have at the back. So you could be braking very gently (as far as you're concerned) and be pretty confident because the front is stable and then wonder why you are suddenly facing in the wrong direction because there was a very rapid loss of traction at the rear. It's the sort of traction loss you are very unlikely to catch at any speed over 5MPH.

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.

Frankly, the YouTube video posted previously should be sufficient to stop anyone from putting on just two - it makes all of this very clear. It is utter madness to even consider it and make no mistake, you are a danger to yourself, pedestrians and other road users if you choose to do so. C Crawford, if you only live 1 mile from work, you'd probably be better off walking, because you would only be safe at those sorts of speeds.

mikey72

liquidbutindebt wrote: »

If you do decide to put 2 on the front, make sure you put slicks on the rear for maximum effect :mad:

Wow, there's some really scary misinformation going on here. ABS absolutely will not help in snow. In fact, ABS is far _less_ effective under those conditions than normal braking systems. The reason is quite simple. Snow is a non solid surface. When the wheels are locked, it builds up in front of the tyre and assists by providing increased friction and more stopping power. ABS prevents the wheels from locking and so this effect will never occur. The supposed benefit of ABS is that it allows you to apply braking force while also turning (the car will not turn with locked wheels), but again, in snow and ice, there is so little friction available that you basically have two choices. Turn a bit and don't brake or brake and don't turn, this is not really any different under ABS or normal braking.

As for using 2 or 4! You would be absolutely bonkers to run with just 2. While you may get away with it, you can never be sure, and kids do run out in front of cars sometimes. Remember, in winter conditions, far more accidents happen because people couldn't stop rather than couldn't get going! But the biggest issues with a FWD car and winter tyres on the front is that you never really know how much traction you have at the back. So you could be braking very gently (as far as you're concerned) and be pretty confident because the front is stable and then wonder why you are suddenly facing in the wrong direction because there was a very rapid loss of traction at the rear. It's the sort of traction loss you are very unlikely to catch at any speed over 5MPH.

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.

Frankly, the YouTube video posted previously should be sufficient to stop anyone from putting on just two - it makes all of this very clear. It is utter madness to even consider it and make no mistake, you are a danger to yourself, pedestrians and other road users if you choose to do so. C Crawford, if you only live 1 mile from work, you'd probably be better off walking, because you would only be safe at those sorts of speeds.

So what you're saying is in effect summer tyres will stop faster than winter tyres, as they'll lock sooner, so build up snow in front of them, if you turn off your abs?
Not a theory I think I want to try.

mikey72

Pew_Pew_Pew_Lasers! wrote: »

It doesn't matter how advanced your brakes are, if your tyres are physically incapable of maintaining grip on the road surface, they will slide across it. Its simple physics. One day, if you're unlucky, you'll find this out for yourself.

Why must a car always behave by locking the back wheels if you change the front.
I keep seeing simple physics being quoted, but no one has told me which law of physics is it?
So which one?

liquidbutindebt

mikey72 wrote: »

So what you're saying is in effect summer tyres will stop faster than winter tyres, as they'll lock sooner, so build up snow in front of them, if you turn off your abs?
Not a theory I think I want to try.

Nice. Not sure how you conclude this, because I didn't say that at all. Clearly ABS will work better with winter tyres, they are designed for traction in snow. However, you will have jack all grip at the rear if you don't put winters on there as well.

liquidbutindebt

mikey72 wrote: »

Why must a car always behave by locking the back wheels if you change the front.
I keep seeing simple physics being quoted, but no one has told me which law of physics is it?
So which one?

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