According from Tire Rack: <a style='text-decoration: underline;' href="http://www.tirerack.com/winter/tech/faqs.html#y4" target="_blank">http://www.tirerack.com/winter/tech/faqs.html#y4</a>
Why Four Winter Tires? I Thought I Would Only Need Two.
Today's winter tires are better at providing ice and snow traction than ever
before. The technology used to develop the tread designs and tread compounds
has evolved beyond what you may have used previously. Every one of our tire
manufacturers and 7 out of 10 vehicle manufacturers recommend four winter
tires be used on rear wheel, front wheel or four wheel drive vehicles. This
is because if you use two dissimilar types of tires on your vehicle, you'll
have a vehicle that has a "split" personality. One end of the vehicle won't
react and perform the same as the other in the dry, wet, slush and snow
conditions you'll encounter before the end of winter. Especially in
emergency situations, you'll find that your vehicle will probably understeer
in one condition and oversteer in another. It is preferable to keep your
vehicles handling as consistently as possible by "matching" all four tires.
Our customers who have matched their tires tell us they're glad they made
the extra investment in four winter tires (and wheels) so they can
accelerate, brake, handle and better control their vehicle through winter's
challenges.
So basically, always install four winter tires, no matter how "good" your
all season tires are on the non-driven wheels (ie: the rear wheels of a
front wheel drive car). Using different tire types on the front and back of
the car can create unusual or surprise handling responses at highway speeds
or during sudden maneuver driving. You want consistent handling - install
winter tires on all four wheels.
"John Doe" <JohnDoe.RemoveThis@JohnDoe.com> wrote in message
news:hGNrb.229865$0v4.16858017@bgtnsc04-news.ops.worldnet.att.net...
> Can anyone help me with this dilema?
>
> My story: I have had my 96 Previa in Chicago for years now and love it -
> except when there is packed snow and ice. Believe it or not, that's not
> usually a problem, even in Chicago. It's hardly snowed for the last few
> years and the road folks get it cleared off quickly. If there is snow pack
> or ice, we usually try not to drive the Previa.
>
> This year my wife needs to drive the Previa every day to school. I jusat
got
> new tires, but also want to get 2 winter (snows) for the back. I've had 2
> places (including Tire Barn) say they won't sell me 2, I need 4 or the van
> is not safe. Come on, I tell them, it's a real wheel drive van. Growing up
> dad put rear snows on his GM & Forn rear wheel sedans every year. I've
> never heard that being a proble. The real cost in 4 is in the rims and
> storage space, not to mention the road noise, plus initial cost.
>
> Is there a tire expert out there that can convice me that I need 4 winter
> tires?
>
>
> Thanks
>
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