Sit On Mowers

[willyboy]

I have an old sit on mower which STILL works fine.
It sort of has everything that a new mower has, just not the looks of a new one!
However, it does not seem to grip when l'm travelling sideways across a slope and any sniff of some wet grass underfoot, and the back wheels just keep spinning on the spot.
Also, the tread on the rear tyres isn't the best, but then again it's not that bad.
Should l -
Get some new rear tyres with a really chunky tread.
Laden the back down somehow with some concrete blocks to give more traction.
Get a couple of snow chains for the rear wheels to give them more grip whilst crossing the slope.
Any suggestions?