Glyn this was my reply to Sharpo about my experiance with a 180 compared to a 190 rear tyre,plus and little about "pushing it"
You may of noticed that I had a 180 rear on at Cadwell and not my previous 190 that is f you could of got close enough
"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
With the 190 on the back I think you will see less wear on the front edges
Fordie