I can get 17.5 Dayton rims that will replace the 15" daytons on a lowboy trailer like these:  http://www.southwestwheel.com/store/p-4605-175675tldmrw.aspx

They also make 22.5"  & 24.5" rims.....would they fit the same hub diameter as 17.5's or will they be for a larger hub?

 http://www.southwestwheel.com/store/p-4606-225825tldmrw.aspx