Ive got 7j 14" Alloys...right now have 185 55's Toyo proxies fitted. (in reality nothing that could be called stretch haha)
My old alloys 7j 15" had 195 45's...no give in the tyres though. I'll be honest im not sure what combo you'd need to go to get them the same as 195 45 but using different tyre sizes. But a deliberate stretch can save you money -- basically why it started in the first place 
I guess you could say 195 45's are the default, no messing about size for speedo accuracy. -- probably why they are mentioned so much.
