In the old days, 50's and early 60's. I lived north of Dallas, Texas. I remember some heavy snows and icing back then. I had a car that weighed about 3200 pounds. I usually ran 35 psi cold in the tires. But when it snowed and was ice on the roads I would let them down to 28 psi cold. Somehow they gave me more traction on the snow and ice.

Tires have changed a few times from back then. Nylon, fiberglass belted tires, radials. I doubt lowering the tire pressure would help any with todays newer designed tires.

 

The basic physics still apply. If you reduce the pressure, there is more rubber on the road, so more traction.

 

I do not mean to start a long dispute on this subject, but I am sure I have read that the thin tires (those of you who remember the "old" days)offered much better traction than the wider tires of today. Mud and snow offered much less resistance to those thin tires, not sure about ice. Can anyone verrify(sp) this.

 

By "thin" you mean skinny? Yes. The reason is that because the patch touching the road is smaller, there's more weight over that patch and the idea is that it helps the tyre grip the road.

With a wider tyre, the weight is distributed over a larger area so less weight per area (say square inch) on the patch.

 

The PSI of air in the tire is about the same as the PSI of the tire to the road surface, and the PSI * rubber_area_on_road = weight of car. On a dry surface maximizing rubber area increases traction, however on a wet surface hydroplaning occurs if the pressure is too low.

 

Hi

I live in Canada and bought my TCH last winter. I went thru a full cycle and can share some of my experiences. I do not do much highway driving in winter and so I will not comment about it.

1. The VDIM does come on when the snow on the ground is not fresh or when you are driving in a snow storm where several cars have used the path. The VDIM does help the TCH in not swerving out of control. I do not use snow tires and did not find a need for it, as my car was so new at that time. I will know more this winter.

2. Too early to comment. My experience was very good last winter and the car was very new.

3. Regardless of snow tires, your MPG will go down. Let me put it in Canadian measures - I can drive about 900-1000KM on a full tank of gas in the fall-spring times (very little use of heater/air-conditioner). I used to get only 700KM on a full tank during the winter. Be prepared for this efficiency loss as heating requires the gas engine to run. If you have a block heater, it can help.

4. I have not used the 'B' gear as I did not find a need for it till now.

I also noticed another important lesson during a snow storm last winter. When there is little visibility and a lot of blowing snow, you tend to drive at less than 30 KMPH. For argument purposes, this is a speed at which the battery can take care of moving the car. Yes it does that, but the car needs the ICE to heat the cabin. It does feel weird when you drive at such low speeds and you find that there is a drain on both the battery and the ICE. That's the nature of the beast. I also find the TCH heater not so quick.

Cheers

 

I'll also point out that driving through ground snow will take more energy, so that's one more FE hit. You're basically going uphill constantly in a weird way as your tires push up against the snow in front and have to climb it (aka compress it beneath them). You can't coast nearly as far without losing speed, so in addition to heating (which I can usually live without--I'm out of the weather, and I have a winter jacket on, so why do I need heat blasting? Except when the windshield is in need of defogging/defrosting), and getting/keeping the ICE warm, you have simple driving conditions sucking up fuel as well...