Do you think this could be related to tensing-up and not pushing on the wheel and sitting all the way back?
I don’t think so. It’s more of a relaxed, more reclined position where my hips are forward and my shoulders are lower. When I push on the wheel, I get more pressure on the seat through my shoulders (than if I’m sitting more upright.)
What about vertical weight distribution?
The idea of balancing all four wheels (to 43/57% front/rear) in an X/Y plane is straightforward enough, but are there any (dis)advantages to where weight is relative to the ground?
Is there an ideal vertical position for COG?
I’m not sure I’ve ever seen an actual measurement of vertical CoG, but where you place the weight has a big effect on that. Generally smaller drivers like to mount the weight up higher to get better weight transfer and unload the inside rear wheel better.
Taller drivers tend to mount weight low to keep from over flexing the kart with their higher CoG.
We don’t measure the CG, but we do manage it. My son is 6 foot 4, so managing front to rear weight and vertical weight are both things that we have to do.
We run 25lbs of lead with 10 lbs up front, this is because his long legs and reclined seating tend to move the weight balance rearward. The remaining 15 lbs gets moved around on the seat.
Typically we have:
-5 lbs under the left front lip of the seat, more front and more left and lower CG.
-5 lbs on the left side of seat, more left and lower CG.
-5 lbs on the back left side of seat low, more left and lower CG.
More grip will keep the back weight lower on the seat.
Less grip will raise the lead on the rear to improve rear weight transfer. If not enough will move lead front front seat lip up on back of seat to raise rear CG and increase weight transfer. If sill not enough, will swap front 10 lb with seat back 5 lb, this moves the weight balance rear and raises the rear CG more, adding more rear grip.
Typically the only move we make on race day is the rear lead up or down, keep the change small.
For vertical CH height, if you have a set of scales and an angle gauge you can use this calculator