Well the best place to start is here...
Alloy Wheel & tyre fitment calculator - it calculates inset, poke, speedo error, tyre stretch and loads more.
www.willtheyfit.com
I'm going to hazard a guess you're running OEM tyre sizes (225/40/18) and that you want the JR11's with an ET of 40?
View attachment 238011
You should be fine using your tyres but... you will have stretch and another place to look will be the internet again for what that may look like....
TyreStretch.com is a reference gallery of real-world tyre stretch fitments, showing how different tyre sizes actually look on different rim sizes.
tyrestretch.com
View attachment 238012
Thats a fair bit of stretch tbh, but thats how a Michelin reacts to being stretched, other brands don't react like that.
Mike