If that is a stock rear rim on an X, I have a 205 65 16 CT on mine and it clears.

 

.....

no, it's a front on Vstar 650. I am turning it into a bobber for a customer and need to know what the biggest tire I can put on a 3.00" wide rim is. There's plenty of clearance, more than I will need. I just need to know what size tire will fit on this rim safely.

 

what tires for your rim

This might help rim to tire app. Ride Safe Grandpadave
http://www.kawtriple.com/mraxl/tire_rim.htm
looks like a 150/80/16