I think one thing to keep in mind is that different karts have different materials or different designs that may influence how they flex, which will change how you tune with axles.
Growing up on a variety of other European karts, it was always “go softer on the axle to free the kart up”, but for the OTK kart it’s the opposite. My theory has always been that the OTK kart flexes differently because the tubing is different material, so the way it interacts with the axle is different.
This is something me and some friends have been discussing. Around here most OTK karts eventually break and need to be welded. They seem to be shorter life race bred machines compared to some of the other manufacturers.
Thanks TJ. I am glad to hear that OTK is opposite of many other Italian brands, that at least makes me feel like I wasn’t losing my mind… however, it gives me little faith that it’s accurately understood across the industry. I believe that two kart brands would react differently for sure, but i am not smart enough to envision how they would react opposite of each other. This is when my friends at the track would say “quit overthinking it and throw in a soft axle”. And if that doesn’t work try a hard axle”. Ha. And they would be right!. But I think most people on here strive to truly connect all the dots… I’ll try the axles but I will never quit overthinking it!!!
The more I think about this the more I don’t see the axle stiffness doing anything but effecting rate of rear weight transfer / lift and that of course directly relates to the front stiffness. Given no other change, it seems a softer axle would provide less rear roll resistance thus loading the outside rear slower than with a harder axle because the outside front would be taking lateral load quicker in response to being ‘less’ less resistant to the roll moment. I could see this adding rear grip on early entry due to two tires contacting longer but adding more potential binding to exit because setting down on two tires sooner. Essentially like adding more front bar. If you are already max front bar, then a softer axle would give you more adjustment I think. THIS IS NOT ADVICE BUT MY THOUGHTS TO SOLICIT COMMENTS… does anyone think that makes any sense? By this logic OTK would be right that a harder axle would ‘free’ up the kart. It seems it would lift earlier and set down later. And if you had oversteer issues, they would be more obvious on entry and exit as the kart would be unloaded earlier and later. If CG was too high or rear too narrow and you developed too much lift to the point of a hop (or close) then I think a soft axle could potentially help, but only because the extra deflection (debatable) would create a bit of negative camber that could fend off the hop. Of course the right adjustment would actually be to lower CG and or widen rear track. My head hurts! Ha. Please blow holes in this theory!!!
I think you are on the right track here. It definitely depends on the flex in the chassis. However, the flex I think is also in the waist not just the front end. From what I have gathered, OTK chassis’ have more flex in them than others. Comparably, the axle deflects more or less depending on the stiffness of the chassis. For OTK, hard axle stiffens the chassis and slows down inside wheel lift from flex. On a stiff chassis, a softer axle may soften the chassis and slow down the mechanical wheel lift. Both variations can achieve the same effect, but for different reasons.
I grew up around cars and auto racing. Many of them had torsion springs on the front suspension arms. I like to think of a kart chassis as a torsion spring. Some springs are soft and some are stiff. Depending on their spring rate, you can adjust other things around it to achieve the desired result.
The front bar can stiffen the front end (between the wheels), but little effect on the waist. So if you have maxed out the front bar on an OTK, then the next step would be a “harder” axle. On a stiffer chassis, if you have taken out the front bar, the next step may be a “softer” axle. Its a means to an end. Control rate of lift. Given the spring rate of the chassis, it may be necessary to approach it from a different angle.
Thanks Greg. You bring up a good point about the waist I didn’t consider. Given it’s not adjustable I sort of left it out, but it certainly is a 3rd element to consider. My aging well pickled melon thinks It would reduce roll resistance for the front but without mandating deflection about the stub axles (front bar, spindles, front of frame, etc) to do it, allowing one to still have a stiffer front geometry for responsiveness and accuracy while not dominating the rate of load transfer over the rear… due to the softness built into the waist And the overall ‘low’ roll resistance. Do I have that right? And me thinks this is especially soft AND springy on an OTK compared to most others. This is probably why you never see an OTK without a front bar! And that springiness, which seems to go away over time, may be getting the rear to lay down faster to allow a setup for a long lift but ‘springing’ it down when it starts to unload to manage oversteer on exit that so many karts get when they get too soft on the front and Also have an understeer condition and then the unloading causes the front grip to go way up but with still only 1 rear wheel on the ground. This is quite genius of OTK actually. - assuming this mess of thoughts I just had is even remotely correct!
Again, I appreciate the reply! Unfortunately I am not able to visualize going to harder axle in OTK when out of adjustability for front bar stiffness. I must be missing a key piece of understanding (which is not so uncommon for me 
). If you were max front bar and you wanted even more front bar, I assume to increase front roll resistance compared to the rear to slow the rate of lift, why would one go to a harder axle in OTK? I’m guessing there is some effect here besides roll resistance that I am not considering… thanks SO much for your help and dialog. I’m learning and confirming a ton.
Edit: you said spring rate, not softness! I get it now. The variation in spring rate among different Mfg’s is a key attribute beyond just how ‘soft’ or ‘stiff’ the chassis is… ah ha moment for me. Getting it to deflect is one thing. The rate of change of force to further deflect is another! Now the torsion bar example also makes sense. Thx!!
I am just saying an axle change is a Big Change. It seems to be something you do when you run out of other, less dramatic adjustments. In my limited experience with axle change, I believe you may have to undo all the little changes prior to the axle change to pick up where those adjustments left off. Or maybe you throw another axle in because you know your settings cannot not compensate for the amount of change needed. There are others on here that are far more experienced and knowledgeable than I am when it comes to axle changes and brand variations.
The front bar is just another way to adjust the spring rate of the chassis. If you look at how a chassis twists under loads from front corner to opposite rear corner, it is basically a big spring. Front bars and axles can change their rate of flex. How they change it depends on the chassis design and materials. As I keep hearing, OTK are very flexible out of the box, but like a spring sprung over its limits their performance falls off very quickly compared to other brands that have less flex in them. It was probably not the best choice for me being a tall heavy guy, but hindsight is 20/20 right.
Ive notice alot of tony cadet karts running lower rode height in front. We run our middle front middle rear. Which works great for us in grand junction but we really struggled at action getting the kart to rotate. We had rear width past the end of axle. Quite a bit of negative camber(helped a little) and a super hard A axle