Re: What does Sniping tires do?

Watch out for snipers.  What you were told about was siping, not sniping.
 
Sipes are small slots that are cut or molded into a tire tread surface.  
On snow, ice, mud, and wet road surfaces, sipes usually increase 
traction.  This name comes from John Sipe, who received a patent in the 
1920's, after discovering that a series of small transverse cuts in the 
heels of his shoes gave him better traction.  In a later US Patent to 
Goodyear, it was claimed that sipes improve tire traction characteristics 
as well.  It also claimed that sipes tend to close completely in the 
tire 'footprint' on the road. 

Tire tread block shapes, groove configurations, and sipes affects tire 
noise pattern and traction characteristics. Typically, wide, straight 
grooves have a low noise level and good water removal.  More lateral 
grooves usually increase traction. Sipes are small grooves that are cut 
across larger tread elements.  Up to a point, more sipes give more 
traction in snow or mud.  

But, as is often the case, there are compromises.  Winter tires, and 'mud 
and snow' tires generally have sipes, perhaps several thousand of them.  
They may feel 'squirmy' on a warm, dry road.  Racing 'slicks' are used on 
dry roads to get maximum traction.  These have no sipes, no grooves, and 
no tread blocks.  They also have very poor traction on wet surfaces.  Tire 
manufacturers use different tread rubber compounds and tread designs for 
different tires usages. 

If you already have tires that are best for dry roads, and you expect to 
do most of your driving on wet, muddy, and snowy roads, then siping your 
existing tire treads may be justified.  You can find more information in 
following URL's on tires, tread design, and siping. 

www.dunloptire.com/glossary.html

www.michelin.com/us/eng/tire/guide/terminology.html

www.yokohamatire.com/04a3.html

www.intlscience.com/TranslatorsCorner/TireTerminology.html