I picked up a new kart over the offseason and I’m doing scaling/ballast mounting over the weekend. I’m 120lbs, 5’7ish. I have had trouble getting any jacking in my previous karts, which made understeer an ever-going problem. I did get a bit more front end with some chassis adjustments, but I’d like the kart to do what it’s intended to do before straying too far from baseline.
As I go to mount the weight, I wonder if I should place it higher than I normally would. I’ve heard shorter guys should aim for ballast to be mounted higher on the seat, and while I’m above avg height for a woman, I’ve always felt I fall into the “short guy” category as a racer - and should set the kart up accordingly.
I have quite a bit of weight to put on, so I figure I’d shoot for the best height BEFORE testing and moving it around. Do you guys have any thoughts?
I’m similar size but a bit heavier and I’ve always mounted my weight high, starting at the top of the seat and working down. I’ve generally had to set my karts up with a lot of weight jacking my whole life. For example, my standard baseline setup has the rear ride height raised up.
A few weeks ago I actually recommended this to a friend of mine whose daughter races 100cc at our track. I noticed how he had a ton of front end in the kart and questioned it, his answer being that if he takes any away she doesn’t like it. After watching her practice a bit, and seeing very little weight transfer and jack I recommended him to move some weight up. The next weekend he moved like 20-25lbs up to the top of the seat and up that inside rear tire came. He was then able to pull some front end out of the kart since the kart was now working like it’s supposed to. Generally speaking women have a lower center of gravity compared to men due to differences in build, so even comparing to a guy of similar height I would expect a woman to need to mount more weight higher to get a comparable COG and weight transfer.
Meaning they had made adjustments that would add lots of front grip theoretically. Some of said changes were really wide on the front track width, stiff front bar, more positive camber, etc. All of this was to overcome the lack of weight transfer so they were basically forcing it to turn, but once the weight was moved up enough to flex the kart properly and pull the inside wheel then it no longer needed to be forced.
Yes, weight higher on the seat. The other thing you can do is to mount the seat a little higher - it really doesn’t take much. As my daughter has grown, I’ve gone from mounting 2 sprockets above the bottom of the frame rails to 1 sprocket, because even as she’s getting taller, she’s still slim, and can struggle to jack the kart.
My son is 5’10" and weighs about 140. We’ve tried raising the seat and putting the weight high and created a rear wheel hop problem. He runs a Comet Eagle.
5’10 is pretty tall to be raising the seat/weight. A driver who is 140lbs but 5’10 generates a lot more weight jacking than a 5’7 driver of the same weight.
Hopping isn’t necessarily bad. Obviously it isn’t an ideal handling characteristic, but at least the frame is working and flexing. Typical it means you are just over that knife edge of the kart being totally hooked up, so widening rear track in 5-10mm increments until the hopping settles down might put you right in the window.
Getting back to the original question… Female has issue with getting frame to flex such that it properly jacks inside rear wheel…
From a purely physiological stand point, women have a lower body mass index in their upper torso than men do. As a result, women will need need the ballast to be placed higher on the seat than a male of the same height and weight. It is just physics. It comes down to where your center of mass is relative to the rear tires.
Your center of mass makes a triangle with the rear tires. The relationship of Height of that mass to the Width of the rear tires changes how weight is shifted. Depending on your specific body type, you may need to raise or lower ballast to assist in weight transfer. Once you match your body type to the geometry of the kart, the other chassis adjustments can be used to fine tune to the environment you are racing.
One of the better explanations of the relation of driver mass to ballast to weight transfer - this is everything distilled down to a manageable construct no matter the experience level.
Poor short guys