Rear tires skid easily because of simple Physics..

as you decelerate your body mass is shifted forward. that unweights your Rear wheel .

Your tire is fine , Technique is needing work,, use your Front Brake.. !?!

lessen the rear brake, so it wont skid, as the weight of your mass, You,

is , in essence ,still in motion as you are stopping the Bike underneath you.

http://en.wikipedia.org/wiki/Newton's_laws_of_motion

http://en.wikipedia.org/wiki/Momentum