Thanks to all who responded ... I think I'm going to stick with the existing Duros for now and see how they work for me.

Recently acquired a Wombat with Duro HF307 tires..... 3.25-19 front and 3.50-17 rear. Not sure why previous owner(s) changed from original but not wanting to change wheel size, any suggestion as to a more aggressive motocross style tire? My competition days are long gone but will be trail riding. Or...