Directional Snow Tires

[MikeySoft]

Some snow tires have directional threads like the Michelin Arctic-Alpin.

I believe directional tires are directional by the way the thread channels the snow/dirt at the contact between the thread and the road.

The threads of directional tires are V shape with the wider part of the V at the front part on the road/tire contact. Extreme examples of directional tires are tires on tractors and monster trucks. When a tire slips, the snow/dirt is channeled up the V and out both the left and right sides of the tire while still at the contact with the road. This gives the thread more bite and better traction. Snow/dirt is also expelled from the thread when the thread is no longer in contact with the road as non-directional tires do.

Now, with breaking, the force between the tire/road is opposite, while the rotation of the tire is the same. The force between the tire/road will now channel the snow/dirt down the V thread and into the center of the tire. The snow/dirt can only be expelled when the thread is no longer in contact with the road as non-directional tires do. The thread will not have the additional bite. Channeling the snow/dirt to the center of the tire "may" make it harder to be expelled when the thread is no longer in contact with the road. Causing additional traction lost.

Questions:
1. Is the above theory correct?
2. If my theory were correct, would it be better to reverse the mounting of back tires of a front wheel drive car? The would give more traction to the back to help keep the car stable while breaking.

 

[Doug C]

While that seems logical, it isn't. Just put the tires on in the direction of rotation, like the manufacturer recommends!

This brings me back to many, many years ago, in my youth, when I tried to figure things out. The car was a 1964 Galaxy 500 (with a 390 4bbl) it was sweeeet! But I digress... the road was snow packed and icy, so I figure that if I am going about 35mph, engage the emergency brake, lock the rear wheels, then put it in reverse, release the brake and voila, reverse thrusters! Wrong... no posi-track rear end!

That made me realize that some things should not be screwed with! (BTW, it fishtailed but I recovered when I dropped it back in drive!)

Cheers, Doug in Colorado

 

[MikeySoft]

quote:

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Originally posted by Doug C:
...
This brings me back to many, many years ago, in my youth, ...

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That reminds me of my first FWD car when I was young and foolish. I used to like making right angle turns in the snow with my old RWD car (64 Buick Special with manual trans) by giving it some gas into a turn to slide the back end around. With the FWD car, I had to put the parking brake on into a turn, and then release it, presto, I did a right angle turn with my FWD car.

Back to the main topic, could anyone explain why my first post is good or bad?

[ December 16, 2003, 12:08 PM: Message edited by: MikeySoft ]

 

[SL8Brick]

I'm not a tire engineer and will never claim to be, but this is how I understand it....Most modern snow tires(directional or otherwise)actually rely on snow retention in the tread to help maintain grip on snow covered roads. For some reason, snow-to-snow contact is better that snow-to-rubber contact. You can actually see this on many modern snow tires. When the vehicle comes to a stop, the entire tread surface is encased in snow. The downside to this, from an engineering standpoint, is that the tire also must be capable of evacuating water on wet roads. For years, many tire engineers found themselves in this snow retention vs.water evacuation quandry. It seems that the tire mfgs have the problem licked now. Many of the latest snow tires can handle wet roads nearly as well as dedicated rain tires.

 

[geeeman]

My experience over the last 10 years with directional snowtires...

It makes no difference which way you run them...

Snow traction was the same, wet grip the same, and even sound was the same.

Maybe if you went 100 mph on a slush covered road, running them "backwards" might be a problem.

 

[S2000driver]

I use two directional winter tires: Arctic Alpins (CRV) and Bridgestone Winter Duellers DM-Z2 (Element).

If you are constantly in below-freezing temperatures, I would suppose reversing the tread direction would gain fractional benefits. However, the loss of wet weather performance is most likely a greater degree worse.

Where I live, this past week I experienced both snow-packed roads and others that were wet and slushy--all at the same time, just turn the corner. The directional tires are performing wonderfully.