wheel sizes for a offset dirt kart

stagger on axle goes by size of the corners - less stagger for longer sweeping turns. using different wheels for mounting tires will change the tire measurement - narrower wheel will allow tire to be taller & allowing more side wall deflection.
Just a note: I don't use LR rim width to get stagger. The 8.25" rim will tend to bite a little harder than the 8.5 but with the high left, high cross setups the 8.5 will typically turn a bit better.