I have a 2014 4" lifted Quigley 4x4 E350 van which is going to get new tires, something with a more aggressive tread. Does anyone here have any experience regarding the maximum tire size I can put on this van? I suspect that I can go a little larger than what is "factory spec" due to the extra clearance with the lift. Thanks for any info or references.

 

You might consider checking with a tire shop or sales place. They may not want to do the change due to liability issues, but you could.

What might show up as a problem could be when the front wheels are turned to the maximum position in either direction they might hit the frame or other suspension parts. Then other measures might be necessary.