Why does my tyre stretch look better on the inner rim?

Just put some 165 50 15s on my 7j zender rims and the to the outer of the rim there doesn't really look to be a stretch but the inside of the wheel there is a very noticeable stretch with the lip nicely exposed, any suggestions where i have gone wrong? Would fitting the tyre from the back of the rim make any difference in the way it pops on or is it just the wheel rim shape???

Any advise would be great???

I've no idea  …..
But  would be really  great if anyone  could put up some information about  tyre's being stretched  / fitting and  sizes/ safety  guidelines 

Anyone???

Odd one I've not seen before. Assuming the rim is the same both front and back on the wheel then maybe it's down to the tyre construction?

It should be uniform internally, but is it an asymmetrical tread? Maybe that could cause it?

If you Google  stretched tyres sizes/  fitting  there's a few useful site's  but I  couldn't get them to link  / copy 

Here's a 7J x 15H2 Zender Sport with et12 and a close match for your Sterns. Even if the off-set isn't the same, the inner profile won't be that very different.

As Hairyarse says and you can see from the images, the inner / outer bead seats match one another… it must be a tyre construction or fitting issue.

The tyre on the second rim in the remaining pictures, is like yours 165/50 x 15.