Some driving technique clarification

My original fault was that I was convinced of the opposite…in my mind if I coast I keep the IR unloaded thanks to the G force that push my body on the outside, and as soon as I touch the throttle I exit from this situation because the IR goes down. But you are saying the exactly opposite thing, so now everything has more sense to me.

@tjkoyen This is counter intuitive to me as well. Is it the tension applied by the drive chain when you first start accelerating that helps keep the inside rear tire unloaded, and then as the acceleration forces build, resulting in load transferring to the back of the kart, that energy overpowers the chain tension and plants the back end of the kart?

Maybe I’m dumb… But it seems to me (and feels to me in the kart) that when you are accelerating, the centripetal force is increased so the kart’s weight transfer plants the outside tires and helps the inside rear stay teetered up longer.

Agree. You are accelerating with wheel turned and therefore the energy is loading the outside of the kart. Mass is moving in the direction the fronts are pointing, not the direction you are traveling, which is outside and away from kart. As the fronts get straightened, the rear wheel begins to descend.

If I am not mistaken there can be a couple wheel drop/lift moments. Straight line braking could bring the wheel down but the act of releasing brake, turning in, gas,… lifts it again. As you a accel and straighten out, down it goes again.

Braking sending weight forwards makes it real easy for the kart to get up on 3 the moment the fronts turn.

Just sorta thinking out loud and visualizing.

There really shouldn’t be if you’re blending the inputs correctly and being smooth. And the inside rear wheel probably shouldn’t be coming off the ground when you’re braking in a straight line. :wink:

Agreed that I practice it doesn’t. But, imagining it… wheels dead straight, traveling straight line down the track to a big braking. You’ll be all 4 down but as you brake, that changes. Wheel is down, then up as weight goes forwards/turn-in, then comes back down on exit. Yeah I guess immconfusing the approach with the act of cornering, here.

You can also pre-load the turn with weight shift on entry, the zig to zag. Aim away from line (outside) so turn in has an extra couple degrees to go so your turn in is bigger/more loaded. It sorta speeds up the transfer, making the wheel lift moment faster/more severe.

Oh re coasting: it’s pretty clear that the kart like turning best/quickest when there’s no power being sent through the chassis. But quick lifts allow you to not coast and use those moments of weight shift (from the lift) to rotate like you are coasting. The lifts fit into the energy cycle, allowing you to redirect the kart, presumably by shifting mass from the back to neutral/forward. The lifts are super brief, and throttle comes back in immediately once the kart is settled in the new direction. So, sort of like coasting but without lengthening the turn by bleeding speed until you complete re-orientation like with a prolonged lift.

Well, if you’re dumb, then I’m a maroon because you have probably forgotten more about kart setup and behavior than I will ever know. :grimacing:

Context is important, so I’m assuming we are still talking about the original question (getting around very tight corners efficiently).

Also, I am in no way arguing that what you are feeling is not correct, I’m just trying to understand why it works that way, so, to that end, I’ve got a few questions:

  1. Does the on throttle inside rear lift behavior you describe happen in all turns, or is it primarily a trait of very tight turns?
  2. If it is all turns, then is the effect amplified in tight turns vs large radius turns… or visa versa?
  3. If the effect mostly occurs in tight turns, then since we are talking about applying throttle, is this happening at/near the rotation point, or is this an effect that can be used by trailing some throttle throughout the entry phase of the corner?
  4. If it is primarily something that happens at the rotation point, is it possible that the peaking of (and subsequent release of) load on the outside front tire (as it finishes the entry phase of the turn and begins the rotation phase), coupled with the corresponding increase in rotational forces combine with the initial longitudinal forces from beginning to accelerate in a way that they kind of rotate the energy that should transfer onto, and set down, the inside rear tire past that tire and onto the outside rear tire?
    .
    Or put another way, the elevated rotational force of negotiating a very tight turn negates the expected ‘planting’ of the rear end under acceleration until the rotational forces are counteracted by the traction of the outside rear tire, and when that energy has been absorbed/equalized then the inside rear sets down and normal service is resumed for accelerating out of the corner with both rear tires?

We need a TUTORIAL (The Unified Theory Of Rear Inside Acceleration Lift)! :rofl:

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Oooh I’m gonna take a stab at some of this:

All turns. It’s subtle on longer or less intense turns. Though the wheel may not fully lift, I bet you the inside rear is less planted even though it may not appear to be “up”.

I think you can have throttle in entry phase and still have inside freer than outside. But I think the wheel wants to be down in that scenario, and the steering is what determines whether it comes down. There’s some centripetal force happening because of the mass of kart wanting always to go wide in a turn. Trailed throttle is trying to straighten the kart and sets the stage for wheel to come down once the leaning from turn in peaks and fades.

  1. When you do it right it feels right. The kart settles onto both the rears gently and completely receptive to throttle. It’s super balanced and hooked up. It feels invisible in terms of wheel lift, but it feels efficient. It doesn’t feel like “aha there’s the planted moment”, it just happens seamlessly.

It’s difficult to parse the individual things that are happening during the turning phase, because lots of things are happening all at once. So hard to isolate what is causing what. When you are applying throttle, you’re usually also unwinding the wheel and are at the point where rotation is achieved.

I think there might be some barrier or misunderstanding happening via internet based text…

  1. Inside rear wheel lift increases directly with increased steering input. So tighter corners you will have more lift. In a faster corner, you rarely have a big lift because the steering input is never enough to twist the frame in a way that allows for the inside rear wheel to really come off the ground. In a fast corner, you are inducing rotation with a quicker snap of hands and getting the kart to a steady point of slip or set.

  2. See above, I think.

I’m not really sure how to answer 3 and 4.

Let me try again another way.

Let’s say you have the kart static, just sitting on your floor with no driver in it. You turn the wheel to the right, and the inside rear wheel pops up. Now if you push on the kart laterally or physically grab the rear wheel with your hand and lift it, it will teeter on the front two wheels and the outside rear wheel very easily.

Is this lateral force you put on the kart while it’s static, not similar to the lateral forces that are increased when you start accelerating in a corner, thus keeping the wheel up longer? Warren, is your argument that the longitudinal forces of acceleration counter this and send “weight” to the rear under acceleration, setting the wheel down?

And to reiterate, I’m not saying that hitting the throttle pops the wheel up in the middle of the corner. No matter what, as you achieve rotation, after the entry phase of the corner, you will have to open your hands to straighten the kart as it comes off the corner.

So no matter what, after rotation, that inside rear wheel is coming back down as you come off the corner. My point is simply that if you are on throttle as you start to unwind your hands, there will be an increasing and continual feed of lateral force going through the kart, it will remain “sprung”, and the inside rear wheel will set down at a smoother and more gradual rate. If you turn-in and if you were to not hit the throttle at the correct point (before you unwind your hands), the kart would simply drop, as the kart would scrub speed off and drop the inside rear wheel.

If the kart has so much weight-jacking and lift that it starts to bicycle, you lift off the throttle to set it back down, no? You wouldn’t hit the throttle, that would flip you over. Does the same not apply here?

I’m happy to bow to your superior understanding of friction circles and the math of driving Warren, I think you’ve got me beat when it comes to having an in-depth scientific mind about driving. :sweat_smile:

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I sense a new Korsasport video coming up… :wink:

That is what I thought.

You are the superior kart driver/tuner, I’m just trying to intellectually understand that which you already know and can apply in the real world, so it is I who bows to you. Also, clearly you’ve never seen me do a math problem. :grin:

But, I really think we are on different roads to the same destination. I tend to look at driving as an exercise in energy management, but my perspective is primarily cars, and karts clearly build and release energy very differently than cars, especially when the 3-wheel effect is most extreme.

So…

Your quote (above) answers my question #3… this is a rotation phase thing, and especially a tight turn rotation thing.

Yes and no. For sure yes from a car perspective, and maybe/probably for karts in corners where there is not a huge amount of steering input at the rotation point.

For tight corners where there is a lot of steering input at the beginning of the rotation point (and therefore a lot of inside rear jacking), you have convinced me that rearward load transfer upon acceleration maintains inside rear tire lift in the short term.

What IS (what you’ve described from experience), is what’s important - full stop. I’m just trying to understand the relationships between the forces that make that reality so. If you’re not tired of this all yet, please shoot holes in this idea:

  1. The main factor influencing the IR lift on throttle behavior is the amount of steering input as the outside front tire reaches peak energy/load/traction/slip angle - just before apex rotation begins, and therefore, where the IR jacking effect is at it’s highest level.

  2. The kart is entering the rotation phase of the corner, so the lateral force of the OF tire is being translated from a force causing the kart to follow ‘the line’ into a force causing the kart to ‘rotate’ upon the line. Because of this transition from corner entry to rotation, the driver starts removing steering input to control the energy that is beginning to rotate the kart.

  3. While the rotation phase is beginning, the driver is also starting to apply the throttle (in conjunction with the removing of steering input) to ‘manage’ the rotation rate, by transferring the appropriate amount of load to the rear tires to generate the traction needed to counteract the rotation force.

  4. However, as you mentioned about the impact of throttle when bicycling, there is the longitudinal rotation force caused by the extreme jacking effect. Even though the reduction in steering input should be reducing this, perhaps it’s the introduction of the vertical yaw/rotation force that is counteracting the expected result of throttle-on rearward load transfer (i.e. setting the IR down).

  5. Maybe once all the longitudinal and vertical rotation forces that are counteracting the rearward load transfer effect start to dissipate, then the expected effect of rearward load transfer can exert itself and set the IR tire down.

Anyway, just thinking out loud. :grimacing:

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I’m happy that my topic have given the starting point for such interesting and constructive considerations :smiley:. My lack of knowledge about some very specific things doesn’t allow me to fully appreciate what has been written in the last posts, but I found many interesting ideas.

Still talking about the lifting of the IR, I think we have to keep in mind one important thing (correct me if I’m saying bullshit): we commonly speak of “lifting” to make the idea easier, but in reality the tyre is just unloaded , it rarely lift completely from the ground. If we look at the video that I posted at the beginning of the topic, from the 7 minute when the driver follows another driver, we can see how the rear tyre of the driver in front is raised totally only in one or two turns of the track, and in one of these it raise because the entrance is downhill. Most of the time a more or less small part of the central section of the tyre remains in contact with the asphalt, and the tyre is “only” unloaded, so it has less weight and removes some of the side footprint from the asphalt .

I think that the fact that there is almost always some rubber in contact with the ground means that, as soon as you go on the gas, the sudden acceleration of the wheel combined with the friction with the ground causes the rubber to start sticking to the ground again, rather than being lifted (or unloaded).

By this of course I don’t mean that @tjkoyen theory is wrong, and I would never allow myself to do so given his experience and knowledge. I think it depends a lot by the setup and the driving style, someone (like me) apply gas in a way and at a point that the wheel drops suddenly, others (like TJ) make the kart work in the opposite way.

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This is a polite way of saying “you fat bastards are high jacking my thread. Get a room!”

Hahahahahahahahahahaha I swear it’s not like that. I love all these very technical replies, very useful to improve my style

You’re very correct in your point about the inside rear not fully coming off the track all the time. That could have an effect on how the inputs all influence the inside rear wheel “drop” as well.

Of course all this great dialogue presumes the kart is tuned properly. :slight_smile:

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This is some interesting reading it has clarified some points in my thinking.

In watching karts I see some lift the inside rear quite a bit while others (mine included) barely get daylight under the IR. How much of this is attributed to the chassis? or set up? or driving style? or something else I haven’t listed? Does the amount or height of lift even matter as long as the IR is unloaded?

It’s a combination of all those things.

You can have too much IR lift which could overload the outside tire, but as long as it’s unloaded and not scrubbing and not causing other handling issues, 1” or 4” doesn’t make much difference.

Also keep in mind if you’re running something slower or a harder tire or a greener track you might not see much lift at all.

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Hey Everyone, I hope you’re all good all always :slight_smile:
I just got a few questions and i would appreciate any answers sooo for starters:

  1. What changes do you make to your driving style when are driving a harder or softer axel?

  2. When braking in a kart with front brakes, what feeling from the kart will indicate that i’m braking as efficient as possible ?

  3. I’m driving a Rotax DD2 with a 34 gear ratio in and will soon change to a 33 gear ratio. What changes to my driving will aid in making lower gear ratio work ?

In general, you should trying to drive mostly as smooth as possible or on the tire’s limit as much as possible, so your driving goal should remain the same regardless of what axle or chassis changes you make. When you make a chassis change that makes the kart jack weight quicker, you will need to be extra vigilant to make your inputs precise and not too aggressive to keep the kart from overloading the tire.

Braking at max potential will be right before the point of locking the wheels. Harder to tell in a front-braked kart because you want to stay away from locking the fronts at all really. In a rear-braked only kart, you want to get to that point of chirping the rear tires which will be the limit of traction for slowing the kart.

Lower gear ratio requires more smooth and precise driving. You are losing bottom-end torque so you won’t be able to power out of mistakes or choppy inputs as easily.