If you do a little research you can find out if the '13 Explorer was ever offered with 17" or 18" wheels. If it was, then it's likely that 17's/18's can be found that will fit.
It's OT but I hate the "wagon wheel" trend with the bigger and bigger rims. Looks like crap, rides like crap and costs extra $$.

And yet, even with 4wd trucks (you know, the kind that would actually benefit from having a big sidewall), the higher trim levels all seem to include 20" wheels because "that's what the customers expect."
My new-to-me 2018 F-150 was an XLT model with 18's, but from what I've seen on the Intertoobz, 17's will fit as well. The good news for me is that it seems like the price difference between 17's and 18's isn't that great, at least not as great as between 18's and 20's.