| "Pushing the front" thats when you go into a corner a bit too hot/fast and still be on the front brake ,your'e then "pushing the front" tyre to its limit of adession and a possible spill.
The 180 is the width of the rear tyre (180mm) with a 180 on the rear your front tyre will turn quicker into a corner and lean over in comparison to the width of the rear tyre thus the "Chicken" strip ( where the tyre has not been used)will be wider, but closer to the edge on the rear
With a 190 mm rear tyre because its wider you find the front is slower to turn in and will wear nearer to the edge , as you are trying to overcome the extra width of the rear . Sounds complicated you need to see it more than talk about it. Hope that makes sense 4D | 
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