Wrong size tire?

So I bought a new tire, and it kind of fits weird. Like part of the lip of the tire is tucked further down than the rest of the circumfrance. The tire that came off of it is 130/80V18. The tire I bought is a 130/80H18. Is there a difference in the sizes of tires with different ratings? Any suggesntions?

This has happened at some time to most of us who mount our own tires. The tire isn't seated properly on the rim. Let the air out, break the bead, lube the lip of the tire, and reseat. Sometimes it is really difficult to get tires seated properly. Did you clean the rim of the wheel really well before mounting the tire? If not, you may need to dismount the tire and clean the rim so the tire doesn't hang up when trying to seat. If a 130/80V18 came off the rim a 130/80V18 should go back on. Just be patient and don't use too much air pressure. (In my younger days I would crank the pressure up to 90 pounds to seat some tires; probably not a good idea.) Ed

Yes, it sounds like the new mounted tire wasn't sufficiently "popped out" onto the rim.

Who mounted the new tire?

Good Fortune!

I mounted the tire looking at a youtube video. I did clean the rim (had a bunch of dirt built up in the lip of the rim) and I'm not sure if I really lubed it up that good. I did let the air out and broke the bead but tried to pump it up again and did the same thing. I think I am going to tinker with it some more this evening. Thanks!