Anybody know how accurate this stretch calculator site is?

http://www.willtheyfit.com

 

Not all tires are alike. Some run wider than others even if they share the same specs. The picture that outputs after you put in the specs is a generic one. It let's us know that the tire could potentially be pinched, run square, or be stretched on a given wheel width. If you really want to see how a tire fits on a wheel I would Google image search it. There is a wheel/tire website that actually shows user submitted pics but I can't remember the name of it. Perhaps someone can chime in.

 

http://tyrestretch.com/

Also, I generally keep it "accurate" by comparing in my head to what brand/model tire I'm currently running and keeping that consistent. There is no way to figure things out 100% before you buy something. There is at least 5% figuring out what is going to work for you when you get the wheels.

 

I find it pretty accurate from a numbers standpoint. I'm generally using it just to compare the difference of running the exact same tire on two different sized wheels. When you throw different brand/model tires in I'm not sure how completely accurate it could be. A 255 RS3 is going to be much wider than a 255 all season.