Ok, thats part of what I’m trying to figure out. The first rule of karting is the inside rear must lift to turn so what i cant figure out why would caster make the kart turn less when the inside wheel is clearly off the ground, and how with the inside wheel still on the ground with less caster, the kart rolls freely.
At initial turn-in (lots of steering wheel displacement), the front end (caster, track width and tire grip) does most of the work and serves two functions 1) to change direction of the kart and 2) initially hike the IR. Here you want more front end “geometry”, which is steering wheel angle, caster and track width to a point.
After the initial turn-in (less steering wheel displacement), the lateral acceleration (side g-force) from the cornering acting on the kart & driver creates a force that twists the chassis, which keeps the IR lifted. In this phase of the turn less front end geometry is needed to keep the IR lifted because the lateral force is should be keeping the IR hiked. The IR can be hiked a lot or little by adjusting weights, seat position, axle and somewhat the front end. By reducing the front geometry with the right amount of caster & front spacers (usually less) the front end scrub is minimized and the IR is just skimming off the ground, this is condition when the kart is rolling through the turns efficiently.
Sounds simple but feeling it and then setting it up is not so easy to do and there are other ways to make adjustment to IR hike.