Just getting into karting with my kids this year. On our cadet kart, all the fast karts in our club are running 950-960mm rear axle with a pretty narrow track width (don’t know what it is off the top of my head ).
Our kart has a 1000 or 1040 rear axle I believe.
We bought our kart used and it came this way. It has super short hubs to (30mm I believe. ) Everyone else is using short hubs too.
So with my simple understanding, they are setting there rear axle up to be stiffer? So our track is probably considered high traction?
If I was wanting to get the same results without getting a new axle, could I just put longer rear hubs on? Would that not also stiffen the rear ?
There’s very limited value in copying just one aspect of someone else’s setup. Running the same axle length as everyone but with a different CG and rear height can send you off in the wrong direction. Or right direction. It is more helpful to understand the why. Yes, a shorter axle can be stiffer, but a narrow track width increases lateral weight transfer, too.
One reason why people say that tuning karts is voodoo is because some changes (like rear track width) have aspects that work opposite to each other and the net effect that takes over is kart- and setup-dependent. What I’d do, mostly because it is the easiest option, is raise the rear ride height and see if handling improves. Raising the rear height or narrowing the rear track both have the same effect of increasing lateral weight transfer, but rear height doesn’t change axle stiffness at the same time.
If things improve with more lateral weight transfer, it might be better to reset the height and then narrow the rear. Going high on the rear ride height hurts braking traction, if that’s important for your class and course layout.
Narrowing the rear changes lateral weight transfer because the CG has more leverage over the tires. This is separate from the axle stiffness, so longer hubs + same track width is stiffer only, no change in lateral weight transfer. Changing the width changes both stiffness and lateral weight transfer.