Tires...

I just bought an '02 Jimmy SLS today. The stock tires it came with are Goodyear Wrangler RT/S, 235/75/15. I'm thinking about putting some larger tires on it, but I'm not sure how large I can go without actually lifting it. I'd rather not go that route, so I'm wondering how large I can go without a lift. Any help would be greatly appreciated. Thanks.

I'm thinkn 29in but i'm not sure.