amount of stretch on a given set of tires depending on 3 major factor.
1. Rim width
2. tire width
3. Tire profile
E.g: Say a 215/50-16 will be lesser stretched compared to a 215/35-18.
I've ran a 215/35-18 on a 9J before. Noticeable stretched, but not that extreme too.
It also to a certain extent depending on the brand/model of the tires.