Hello, I wanted to know which settings are the most important to play with when in my position. I am currently racing at a track that has low grip and my chassis is a Praga, which is softer than OTK and therefore struggling with grip. We have 2 degrees of positive caster, a factory setting front track and a 138mm rear track. We have the two torsion bars installed with the rear in the vertical position, and the ride heights at their highest. We are still struggling on corner exit with oversteer and a little bit of bite on turn-in. I am considering opting for a stiffer rear axle. Also, do jecko seats provide more or less grip, since they are more flexible than my standard seat?
Thanks!
Going high level… If its both on entry and exit I’d look at seat position first.
Can you feel the inside rear lifting on turn-in? The rear torsion bar is a curious setup.
1380mm rear is also fairly narrow, especially with added caster. It sounds to me like you’re putting a lot of mechanical weight-jacking in the kart but with the stiff rear you aren’t letting it flex properly maybe? You need the kart to lift to get it to generate sidebite and therefore corner exit grip. If the rear is flat or too stiffly sprung, it will react very harshly when/if it does lift the inside rear and will likely flat-slide on exit.
I can feel it lifting a bit, I think do to the added caster, but I feel like the rear could stick better to the ground, so maybe I will try to take the rear torsion bar out, or put it in horizontal to allow for more flex?
Thanks for the advice!
I can’t think of any time we’ve run the rear bar. It’s an almost never-used adjustment. Even in super low-grip situations.
Working with @chris1388 this past year we learned a ton about low-grip conditions, as his track is also quite slippery.
We basically treated it like a rain setup and that worked well. On the OTK karts, this means softer axle, maximum front stiffness. A Praga may tune differently, but looking at it from the perspective that low-grip situations are similar to a rain setup might be the way to go. Whatever axle you would run in rain, try that one.
The goal is to get the kart to flex easily so you can get it lifting easily, as there isn’t grip on the track to generate forces to twist the kart. You’ve got make it easier for the kart to twist in the rear.
Oh I understand, the track isn’t that low of grip to run rain setup, but still low compared to high grip ones. This is very interesting because we almost always use the rear bar, but maybe it will help because I do need the tires to load up more and make the chassis flex. Regarding the axle, a softer one provides more grip? I always thought it was the other way around.
Depends on the chassis. The OTK always goes to a soft axle for more grip, stiff for less grip. Some chassis require the opposite. There is a large discussion about that topic here: Do different stiffness axles do anything?
Oh ok thank you! One more question, are more flexible seats like Jecko supposed to add more grip? I am considering one, I have a standard hard one.
I’m not sure the Jecko is any more or less flexible than a standard Tillett. We have drivers who have run both and haven’t noticed a big handling difference, just a difference in comfort. Some drivers find the Jecko to be more comfortable.
Altering the seat stiffness will adjust the amount of flex in the center of the kart and change how weight from the driver is distributed to the tires. This can add or remove your perceived “grip” depending on what handling issue you’re fighting.
I’ve talked about it at length in many other topics here over the years; but we aren’t really altering the “grip” in the kart when we make these chassis adjustments. We are adjusting the amount of inside rear wheel lift and how quickly that lift happens, or the rate of lift. Depending on the situation (track conditions, tires, chassis, weight) the same adjustment might offer two different handling effects in different situations. That’s why thinking in terms of “grip” can be confusing.
Instead, think of the whole go-kart as a balancing act. We need to achieve a certain amount of lift to get the kart to rotate but be stable. It’s a range. For example, you might go stiffer in the axle and the kart might feel better. But if you keep going stiffer the kart might start to feel worse again. The goal is to find that sweet spot. And since the grip levels from session to session can change, that sweet spot can move, so the adjustment you made two race weekends ago might yield a different result this weekend.
Sometimes going stiffer can add stability to the rear. But if you’re already too stiff, above the sweet spot, then the kart will get worse if you go stiffer.
Hopefully that all makes sense. It was a little wordy and wandering…
Yes I understand, thank you very much for all the help TJ, I really appreciate it.
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I’ve been told by a Jecko dealer I trust that the soft is a similar stiffness to the Tillett T11VG (which is the go to seat for Rotax and TAG and is soft, but not the softest). The Jecko Close Edge is more like a Standard Tillett T11.
I would personally suggest a stiffer seat with a standard setup (i.e start from the beginning with the new seat). Jecko are all the rage because KR use them but you’d probably be good with a standard Jecko (Close Edge), Tillett (T11), IMAF, Greyhound. Whatever you can get your hands on. If you can borrow a used seat just to try it before buying, even better. I think the IPK seat is a rebadged soft IMAF but i could be wrong.
Then let us know how it goes, its always great to hear what worked.
Thanks fo the info! Yes because the seat I have is the standard IPK brings, but im not sure wich one it is. Anyway, if I want more grip you think a stiffer seat will do better?
Yes, generally a stiffer seat means more sidebite and grip(I know this to be true in (OTK), but it is dependent on tires, chassis, and track material to be specific.
I’d try moving the seat back - just a smidge, 1/4” should be plenty. I had the same struggles with an old Energy Corse, moves the seat back which helped massively on corners that require some braking, but gave me understeer on power corners. 5mm of front track fixed that, now she’s a rocket.
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Just a note on the jecko seats, the older model ones with the coloured edges is equivalent to a tillet T11t…it is a medium soft seat.
Jecko no longer makes the above though, now all thats available new is the silver soft (all silver, no more colored edges) and this is a soft seat… equivalent to a T11VG
I’ve personally run the jecko from the former and on my track which is extremely low grip and a rotax senior application, mounting the seat where jecko said had the kart way too rear weight biased and the kart would not turn…it was only until I shifted the seat forward did it start working better and i was able to turn the go kart
Thanks for the clarification on the Jecko seats comparison.
I was always a little skeptical about the single measurement for all snr classes.