When you look at your tires think about this.
The knobbies on the rear are oriented to help "PUSH" or "Propel" the bike forward.
The knobbies on the front are oriented to provide better traction and control when stopping, or being "PUSHED" against!
Rear tires want to Scoop the soil, front tires want to Grab the soil.
Does that make more sense?
I hope that helps.
L8R
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"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming, "WOW, What a Ride!" - unknown
"Your Bike Sucks" - Sky Yaeger