Korsasport Karting 101 - Lesson 3 : Basic Chassis Tuning and Setup

TJ. Sounds like a TIP JAR (or PayPal or whatever) would benefit the project. Might free up some resources for better equipment, editing software or just subsidize your income. :thinking:

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[email protected] is my PayPal, but please do not feel like you need to donate money to me. I do stuff like this because I love it.

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I race in the same class with my son and while my Dad does come to the races he has a hard time noticing wheel lift. I have given thought to setting up the gopro is I can observe it but that is more of a practice day thing.

As long as the kart is is close to base line set-up and mechanically sound what would be the effects of not enough or to much lift or to late or to soon?

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Thanks TJ, really opens ones eyes

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Any amount of lift other than the “right amount” is going to result in some chassis issue, just depends on how big or noticeable it is.

Too little lift and the kart might understeer as it fails to rotate without scrubbing, or it might feel fine but is just slow and boggy off the corner.

Too much lift and the kart might oversteer as it overloads the outside tire. Or it could hop.

Depends on the other million variables also acting on the kart.

Whenever I’m diagnosing my own kart, I try to start in the simplest terms, mainly the overall balance, and dive down deeper from there to get to the root.

So my thought process during and after a session is something like this:
Balance = oversteer, understeer or neutral?
Can I feel it lifting the inside rear wheel?
If there is an issue, where in the corner does it happen?
Does it lead to another handling issue? Or is it caused by another handling issue? (Understeer leading to oversteer for example)
Is there any chassis adjustment that is set to something out of the norm or is there an adjustment I suspect might not be ideal for conditions? (Like, do we have a soft axle in when we had considered the medium might be better? for example)
Finally, when does the kart come in and go away, for tire pressure adjustments.

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Thanks for the reply.

A lot to think about for sure. Just wondering how much or often did you use scales to help in setting up or adjusting a kart. I would think many of the adjustments covered may have little to no effect on the scales but obviously a very noticeable effect on the track.

I scale once when we set up a new kart, and then never again. Unless I think we bent something.

I don’t tune with scales at all. I know some guys swear on having the kart on the scales every session.

Would scaling be the primary way to tell if your seat position is borked?

Assuming the rest of the kart is straight, yes.

You should be setting the kart up initially using the seat placement guide from the factory and a set of scales to verify weight distribution.

I’ve been at it long enough that I know what my weight distribution looks like when I have the seat and my weights in their normal spot.

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You think it would be worth it to go through that exercise with my dreaded margay? Or am I just throwing more money at it?

Definitely worth trying. Throwing on someone’s scales shouldn’t cost you too much money, and it’s always good to verify everything is in the right place when (presumably) you didn’t personally set the seat yourself.

Thanks!
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When you scale do you set it up ready for the track?
IE air pressures, fuel load, driver suit, helmet, etc

Do you look for weight or percentages?

What is ideal?

Yeah basically scaled ready to go on track. The weight could change a decent amount without your helmet on or fuel in the tank. It’s a good exercise to get your kart on the scale with you in it also just to see how moving your body around affects the weight distribution. Makes it really easy to see and understand how important driver posture is, and how a driver could easily affect the kart’s handling based on how they are sitting in the seat, or working the wheel, or working the heel rests.

I try to aim for 50/50 side to side. Front weight percentage is typically in the 41-44% range depending on driver size, chassis, class etc. Most manufacturers’ seat placement charts are designed to get you near that range based on your height.

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You bring up a interesting point that you mentioned in your video too. What is the ideal posture for a floppy sack of meat?

I have noticed some drivers lean into turns but have noticed other drivers sit bolt upright no matter where they are on the track.

Like anything it’s conditional.

The kart is designed to work with the driver transferring weight into the top of the seat, through the seat struts, down to the bearing hangers to lift and plant the rear wheels. So a firm posture, keeping yourself planted in the seat and pushing and pulling on those seat strut connection points with your torso is going to work the kart most effectively.

That’s not to say you can’t be fast with a different posture though. You might set your kart up a little differently if you lean differently in the seat and achieve similar results. As discussed, you can change the kart’s handling pretty drastically with the way your shift and move your own body weight in the kart. So if the kart isn’t going planting the outside rear enough, you can lean further to the outside of the seat and try to put more pressure on it. If the kart is hopping or overloading the outside tire, maybe you try slouching a bit in the seat to lower the center of gravity, or you lean inward in the corner a bit to keep some pressure off the outside rear.

I tend to keep myself as upright, firm, and leaning outwards as much as possible. The most important thing is keeping some consistent posture. If you’re flopping all over the place, the kart will react to that every time and you’re going to have inconsistent handling issues.

Big topic about posture here: Posture, and head movement

Posture was another one on the list of things I wanted to make a video on.

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TJ – Thank you for the generosity of your expertise and your time. We are so lucky to have you.

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TJ has a video on set-up that ends with something like this: “Never tighten the rear bumper.” After years of driving my Rotax CRG’s or Zanardis with my bumper tight, I’ve recently experimented with it loose, now on a CRG KT2 with VLR 100. While trying to keep apples to apples (obviously same day, same track conditions, same fuel level each run, no change in tire pressures, short time between runs, etc,), I’ve gotten inconsistent results at best. Sometimes tight wins, sometimes loose wins. As I examine my Micron 5-2t data at home, I cannot find a pattern (speed, rpm’s, braking, lateral acceleration) that gives me the answer. Best I can tell, it is usually my driving that is the variable (we are talking no more than 1 tenth between the fastest lap in the 2 configurations, although time differentials vary throughout each lap).
If requested, I can give much more set-up info.
Thoughts?