Tire Pressure and Snow

[Brandon002]

So the other day I decided to play around with tire pressure as my X was having a hard time in the snow on all seasons. went up from 32psi to 36psi and it's a night and day difference. Since the change my X is an absolute beast in the snow, ABS hardly kicks in, understeer is drastically reduced and acceleration is greatly improved.

So if anyone is having a hard time in all this snow, try upping your tire pressure a bit. Might work for you as well

[Helihover]

Please explain more as this makes absolutely no sence. LESS tire pressure equals more traction and this is a proven fact. I used to be an avid off-roader back in my younger days and can remember getting stuck due to loss of traction. I could sometimes break free by dropping the pressure in the tires. Many off-road vehicles have a button on the dash that will allow you to drop the tire pressure for off-roading and then air them back up. Many customs jeeps have similar set ups. It was not uncommon for me to run 12-15 lbs while off-roading and that's without bead locks. Guys with bead locks a would drop their pressure down to 7-10 lbs! All to gain traction.

Please explain how increasing tire pressure increases traction.

[Brandon002]

There is a huge difference between driving on snow and crawling up rocks and dirt. You want less pressure for a greater contact patch when off roading. In the snow a narrower contact patch will allow for better traction.

[Brandon002]

Take it straight from the tire experts.

http://www.tirerack.com/winter/tech/...jsp?techid=168

[upallnight]

I can see that because of the extreme cold that the tire pressure if inflated on a warmer day will be lower due to the cold. I have always used dedicated snow tires on my cars since owning my BMW E34 Touring. Never got stuck with the E34 even though it was rear wheel drive.

[Brandon002]

I had snow tires on all my rear drive bimmers too, they are hella fun to drive in the snow with snow shoes on.

[Helihover]

Ya....... Not buying it

That article, to me, did not come out and say, "you will have more traction if you increase your tire pressure." I believe it's a guide for winter tire use for dummies by a manufacture/retailer to achieve higher mileage by not running your soft compound tires with low pressure. The article also talks about when to check your tire pressure while it's cold.

It's pretty basic to me. Traction is the result of friction. More contact area equals more friction. Lower tire pressure equals more contact area.

If you had two identical X's side by side at the bottom of a snow covered hill and one was running 38lbs on the tires and the other was running 10 lbs, I would say the X with 10 lbs of pressure in the tires would have more traction climbing the hill than the X with 38lbs.

Also many, many of my off roading adventures included snow.

[JCL]

The benefits of higher pressure will depend quite a bit on the type of tire being used in the snow.

Traditional (older) winter tire designs drove from the edges, where there were deep lugs. Those tires only had traction on the lugs in deep snow and so a narrow tire performed better because it cut in more, giving those lugs a better bite. Higher pressures kept the tire shoulders sharper.

Modern winter tires use different technology and usually drive from sipes and blocks across the entire surface of the tread, using different rubber compounds. These tires can stay on top of the snow and depend far less on cutting a deep swath. These tires also have better performance on ice, where pressure won't matter either.

I have never over pressured tires for winter driving. But I have checked tires more regularly in colder ambients, since tires set when it was warmer out will be at a lower starting pressure when it is cold out.

[Brandon002]

So friction when on top of snow is going to give you better traction than friction after cutting through snow?

Think about it for a minute.

When you're off roading you're driving over very uneven surfaces, made mostly of rock, dirt etc... You let air out of the tire so that the tire can conform to uneven surfaces and so that the contact patch is greater.

In snow you want the contact patch narrower, so that the tire can cut through the snow. The more you can cut through the snow the more road you're going to be in contact with.

Again, there is a huge difference between offroading and driving on pavement covered in snow.

[Brandon002]

Why do you think most people with sport package X5's go with narrower tires when installing snow tires?