wheel fitment & tyre stretch

[rcsammy]

So im currently running 15x7 MIM cups all round, i just bought some 15x8 ET18 ATS Cups to put on the rear

Im quite new to fitment, tyre stretch etc so im after some advice on the best way to get them to fit
I tried them on and the lip of the wheel pokes around 10mm out of the arch, i'll put a pic below

what sort of stretch should i be looking at to get the tyres to tuck, maybe a bit of camber? I dont want too much stretch as i live out in the sticks and its my daily.
The arches are already rolled and flared very slightly



Any help is appreciated

[Wayne]

185/50/15 

[rcsammy]

they should clear without adding any camber?

i've got some 185 55 15s in the garage so i'll give them a try

Will i need to run higher pressure for the stretch?

[Wayne]

they should clear without adding any camber?

i've got some 185 55 15s in the garage so i'll give them a try

Will i need to run higher pressure for the stretch?

185/55's will be a little big, 185/50's would be better.