If your dealer got his exchanged from Forest River, they must have
been cracked when brand new!!!
Why isn't your dealer helping you???
That's his job!
My suggestion is to first look at this website and then your tires
to see the date code--
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=11
The last 4 digits tell the week and then the year
your tires were made.
Are they old??
New tires should not be cracking.
Did you get a pile of paperwork with your new trailer.
Are there papers for the tires???
Call Duro and tell them what's happening.
They might just be recalled or they may replace them.
If you don't have papers on Duro tires here is their website.
I'd call them and see where that leads you.
http://www.durotire.com/
Finally, you should file a report with the NTSB but that's not
going to get you any new tires......
Good luck!!