[Coopspeed]

Anyone have a good explanation for increasing the pressure on snow tires?

The following is from the Mazda owners manual:

Inflate snow tires 30 kPa (0.3 kgf/cm 2 , 4.3 psi) more than recommended on the tire pressure label (driver's door frame), but never more than the maximum cold-tire pressure shown on the tires.

 

[arathol]

Softer tires will float more on snow.

 

[M3Nitro]

When in doubt always first go by the recommend tire pressure decal or owners manual, then you can contact the tire manufacture in which they generally will refer you to the fomentation decal or owners manual or simply and easy the best advise use the standard recomend tire pressure on the decal making sure that you check and balance the tire pressures when they are cold and no tire during the checking is directly exposed to sunlight. Naturally find a way to verify the Tire pressure gauge is accurate. You would be surprised how badly a higher percentage of them are not.

You can also contact or read many periodic publications from the NHTSA (National Highway Traffic Safety Administration)

 

[arathol]

Some more detailed information from above-
Snow tires are made somewhat differently than other types of all seasons tires and such. Mostly its the softer compounds and deeper more aggressive tread patterns used to keep the tires pliant in cold weather and maintain grip on snowy roads. Winter rubber compounds translate to tires that don't have the same driving feel as warmer weather tires, they might be a bit squirmy. So, you add 3 or 4 pounds to make the tire response feel more "normal". This also allows the tread to bite better into the snow.
Also to consider is the ambient temperature when the pressure is actually checked. In the winter it can be really cold, meaning the pressure in the tire is lower. Lower temperatures and driving in snow means tires don't warm up as much and shed heat more readily. In other words, if your tires normally have 36 psi @ 65°F cold, and 40 psi hot, at 15°F they may only have about 27 psi cold in them, and may not heat up enough to get back to that 40 psi hot that is normal. So, you need to compensate by adding a bit more pressure.

 

[Coopspeed]

Yes, they feel squirmy. But I love the snow traction.

I was actually unerinflating them. Unknown logic.

Anyhow I'm all set now. Thanks for the explanation.