Anyone run 235/50/18 or 245/40/18 on an R?

No. But keep in mind that 235/40/18 already barely fit. Although I think going to 245/40/18 would have less of an impact than 235/50/18. What's your goal?

As S60 R stated, what's your ultimate goal?

Going to the 245/40 will give you a little more width but you're increasing your sidewall by 4 mm (nominal). That's a little over 1/8" & will not be too noticeable but you will see a slight difference.

The 235/50 on the other hand is a far more significant change. The tire width does not increase but you're increasing your sidewall height by 23.5 mm (nominal). That's almost a 1" increase. You will gain better ride comfort but it will change the look of your car...and IMO not for the better. It will look more like a standard sedan rather than a sports sedan. Again, this my opinion...take it for what it's worth.

Hope this helps! :57:

Take care, Bud!
-Kenny