boat tyre size?

[VTPREDATOR]

so im trying to fill out the self assessment papers to register the boat trailer and have run into a few issues. i have to find the tyre size and ply rating. i have the numbers off the side of the tyre, but dont know what is what? 4.80/4.00 - 8. can someone please break that down for me?

also i have to find the trailer measurements. question #5
http://www.support.transport.qld.gov.au/qt/formsdat.nsf/8947c9bfbd134b464a25669000137547/8f5d6eea0a5d0e0b4a256a330010a07c/$FILE/F3970_es.pdf

how can i find the figure for P when its not a box trailer?

cheers,

[Not_An_Abba_Fan]

4.80/4.00 - 8 is the tyre size. The ply rating will be on the sidewall too, it will probably be 4 ply.

I would say P would be the distance from the front roller to the centre of the axle as that is the forward most point that has load on it. Or, you could just put N/A as it isn't a box trailer.