Because for some reason the shock sits closer to the turret on the nearside than the offside!

If you look at a Sierra from behind you'll see that the nearside rear wheel sits further in towards the middle than the offside (it does on every single one I've ever looked at anyway!!)!!

When I had my accident many years ago, I looked at mine after I changed the beam and thought I'd bent the shell and was about to break it. I then looked at my mate's 3 door, his brothers Saph and another mate's 3 door that was outside at the time and they were all identical!!

Good old Ford!!