[zoombie99]

Is there a major advantage to having the 19"'inch tires included in the Xline package on the X3 over the base 18"'in snow?

 

[Norskie]

Only very little. I'm assuming that using larger diameter tires results in a lower profile to maintain the same OEM circumference.

Lower profile tires have less flex which means they conform less to the surface under it. They also have less rubber and more aluminum ie total weight is also less. That means less rotational inertia so it tire can spin up faster, losing traction. But these are absolutely minimal considerations compared to width, tread depth, tread pattern, and tire formulation (I.e. how well the tire flexes when cold).

 

[Autoworld]

All things being equal, wouldn't the narrower tire have the better traction in snow ( due to more pounds per square inch contacting the road)?

 

[Norskie]

Yes. The op asked about diameter difference hence my answer... But if the increased diameter also implied a wider tread then you are correct, the 19's will perform worse in snow.

 

[jgroarke]

To be honest I never had any problems with my 225(front) 245(rear) winter tyre combo. It's like a bloody tractor