It’s a lot to take in, so you’re right, it’s hard to wrap your head around it all. It can be difficult to decipher because with all the variables at play within the chassis (not to mention the engine and tire combination which can completely flip everything), many things can seem contradictory.
Now, first I would say that trying to tune a 1994 Tony Kart is going to be completely different to tuning a modern kart. Nearly everything has changed since then in terms of chassis philosophy, driving styles, engines and tire compounds etc. Just look at a top-level driver of 1994 compared to a top-level driver of today and look at their posture in the kart and the karts attitude is on-track. Totally different. Modern karts have become heavier, wider, softer, and smoother.
In general, I really try to get people off the idea of “grip” and whether you have too much or not enough. In reality, the more grip you have, the faster you can corner, right? The reason the kart has “too much grip” is because both back tires are on the ground and it’s binding. It’s not a case of “too much grip”, it’s a case of not enough lift. So if you’re trying to free the kart up, you’re trying to adjust the rate at which the inside rear lifts, to get it to lift more/sooner in the corner.
So how do we actually get lift? Well the chassis has to flex. This is a pretty simple concept; softer chassis will flex more, stiffer chassis will flex less. The goal is to get the waist of the kart to twist, so that the inside rear can come off the ground. Take a popsicle stick and try twisting it. Now take a 2x4 and try twisting it. Obviously the popsicle stick twists more easily because it’s softer. It becomes difficult when we start adding components to the kart which can interfere or contradict with the action of the chassis.
Now it’s really important to distinguish between stiffening the frame vs. stiffening the axle. By adding long hubs, you are not stiffening the frame, you are stiffening the axle, and not only are you stiffening the axle, you are only stiffening the very end of the axle. In my very humble opinion with only my personal experience to back it up, long hubs do not add increase the sidebite on the outside tire. I feel like they alter how the tire flexes and reacts/deforms with the track surface, but they don’t let the tire dig into it’s sidewall like a standard hub does. This is just me though. I always run medium hubs, 100% of the time. Rain, dry, sleet, snow… However, pretty much every other tuner I talk to (including my team) disagrees with my assessment, so take it with a large grain of salt.
And this is where we get into the debate of why OTK recommends a hard axle to “free” up the kart. My theory is the way their chassis is constructed, the materials they use, they put the hard axle in to get the frame to flex more. The stiffer axle is going to absorb less of the load, and transfer that force through the frame to twist it more. Some constructors with a stiffer frame might suggest a softer axle, because they are trying to get the axle to flex more. I truly don’t know, this is mostly speculation.
I should also note, that on a green track and hard tires, it’s totally viable to run a super soft setup, and basically slide the kart around the track to keep it free. This is exactly what we did when we ran club races on B’stone YDS tires. Soften everything, get the thing to squat in the corner and just slide ever so slightly to keep the kart from binding. This only works on a really green track though. Once it starts to grip up, you can’t slide anymore, the kart will just be flat and boggy.
If you’re struggling to get front grip and then struggling to get back on the power, I would say address the understeer first, because late corner oversteer generally stems from lack of front grip on entry. Push-kick or snap oversteer is usually what it’s called. It sounds like you’re making the right adjustments, especially if you’re getting faster, so that’s sort of the end-all-be-all of whether it’s working or not. The stop watch is the best judge of what’s working and what’s not.
I sort of rambled but hopefully there’s something useful in there.