Tires: what size to buy, proper inflation pressure, snow traction

Question
I am looking to replace tires on my daughters auto.  A 1999 Dodge Durango, door jam states 225 75 r 15.  She has now 235 75 r 15.  I plan on buying Michelin cross terrains.  The sears tire salesman stated the 235 gives her better traction on dry and wet surfaces.  I thought the narrower the tire the better the traction in wet weather.  Which would be the best overall?  She will be driving 2hrs to college and returning home often on the highway.  I want the safest.  Please advise.  Thank you

Answer
As a general rule, the narrower the tire, the better the snow traction and the better the hydroplaning resistance.  However, pure wet traction (no hydroplaning), a wider tire is better.

But if safety is the most important aspect, then inflation pressure, not tire size, is what ought to be emphasized.

Every vehicle has a placard that states what the original tire size was and what the proper inflation pressure should be for that size.  It is recommended that the pressures be checked once a month, particularly if the outside temperatires are going up or down as temperature affects the pressure.

So get your daughter a pressure guage to stick in the glove box (a $5.00 one will work fine) and have her check the tires once a month.  This is the best and cheapest safety check that can be performed by the average person.

Remember, underinflated tires are overloaded, and overloded tire failures can have tragic results.