Rotation explained description help

If you had to describe rotation: what is it and how it’s done?

I am having trouble trying to articulate rotation. It’s a hugely important aspect of many of the corners in TT. I order to discuss how to take a corner, I think it’s important to be able to explain.

My attempt to describe it is as follows:

Rotation is where you re-orient the nose of the kart either entering or at apex. It is not a slide, it is a directional change that occurs while you are in slip angle. You have the ability to rotate several degrees without losing rear traction.

This is accomplished by having the kart loaded up, entering a turn, for example. As you brake the front end receives the majority of the weight. Under braking, if you push against the Lateral tire grip resistance… literally feeling the resistance of the tires gripping the track, you can lean slightly into the resistance in the steering column and push. This, if done too much, will result in a slide, a little results in rotation. Bake until done and golden brown.

Anyone want to take a crack at describing this? I can do this, but for the life of me draw a blank when trying to articulate. I am pretty sure everyone accidentally rotates to a certain degree, it’s built in to the geometry. So, presumably folks have some experience with it as it happens naturally, to a point. So maybe there’s some key to this that I am missing that is a potential “Aha!, I get it.”

I’m a little confused. Rotation is rotation, I’m not sure what else there is to distill out of it? It’s the kart rotating around the corner.

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Right. How it’s controlled and initiated. How do you explain this to a new guy. It’s a feeling that is also an action. It’s somewhat automatic until you want to rotate the kart earlier.

For example pfi 2nd cut back. You force rotation here.

I refer to the kart rotating around it’s central pivot whilst also turning. The turn within the turn.


If only someone would try to explain this rotation & trajectory stuff :wink:

For example, pages 9, 17, & 26 - 30

This is what I’m going on about. @speedcraft does a really great job of explaining it. What I am trying to find is a “Basic” version that describes rotation conceptually. Initial conversation, not deep dive. Sorta trackside version.

Maybe sorta like @tjkoyen “under rubber” concept. Simple image that is conceptually easy to visualize and feel. It makes you think and there’s a logical way to play with that concept on track until it’s second nature.

Anyways, if anyone has a way they describe to their buddies how they “get the kart around” I’d be curious to hear how you put it.

I believe other concepts take priority when trying to explain technique to someone new. When and how they are initiating movements with their hands is top of the list for me. Keep it simple and focus on:

  1. Hitting marks- correct turn-in points
  2. Smooth hands
  3. Hand and kart should be settled from center off so as not to impede forward momentum.

One’s initial inputs are going to dictate the rest of the corner. While I think you’re on the right track with your explanation of rotation, I believe concept is more advanced, and the above items should first be tackled, along with proper braking and throttle application. Even once someone has a good grasp of all that, I would re-frame the rotation concept to something more along the lines of tire utilization (friction circle would be a data-driven approach), as that will help instill the concept as applied to the duration of the corner, as opposed to trying to focus on the “moment” of rotation.

Most people aren’t going to be receptive to a ton of theory discussions, so the best way to learn and grow is to get laps…laps, laps, laps. Practice, race, lead-follow…as many as possible.

Thank you for your thoughtful answer. I like your suggestion. Indeed, rotation is an advanced concept, one that is subtle and intricately connected to the basic act of turning properly.

And yes, the new karter is best served by focusing on those things you mentioned, so thank you for that.

Agreed. But that’s exactly why I think about these things. There’s only so far you can go unless you start understanding what you are doing.

Friction circle: I’ll have to familiarize myself. Thanks.

I think maybe what we are hovering around here is explaining how and when the kart takes a “set” as I usually call it. Specifically I’m thinking of Evan’s #3 point.

The turn-in phase begins when you spot your turn-in point and initiate wheel input. From there, wheel input will increase to a point, as you load up the kart and get to the traction limit of the tires. Something, something… friction circles. Once you hit that traction limit, the kart can no longer tolerate additional input without scrubbing somewhere. You’ve loaded it up to its max. This is where the inside wheel reaches its peak unload. This is what I consider the “set”, that the kart takes. Where it feels like it sort of is settled or dug down into the corner as much as it will allow, and you can start to unwind the wheel and let the spring of the chassis propel you off the corner.

I think at “set” the kart is doing the pivot/rotation Dom is talking about. I’m not sure the actual trajectory of the kart is altered here, but it feels like you reached your inside arm out and grabbed a pole on the apex and are swinging it around the corner. More of a feeling rather than an actual physical change in the kart’s trajectory.

This correlates with your rate-of-lift and the amount of lift you’re getting from the inside rear. Changing that rate and changing how much lift will alter how quickly you get to that set. Driving will affect it too of course, with each input from steering to throttle affecting how the kart lifts and therefore sets.

In a fast corner, you can feel if you flick the wheel, you can almost immediately put the wheel back to center after your input and the kart just floats through the corner in a controlled, unloaded fashion. In a slower corner, you have to build that up more with a bigger, slower input or you risk going over the traction limit and never really getting the kart to dig or set.

So the way I explain this is always referring to the kart taking a set. That’s terminology I learned from studying iRacing Skip Barber setup stuff like 10 years ago funnily enough. It’s a feeling of the kart being in the track, rather than on top of the track. My drivers seem to understand what I’m talking about when I refer to it this way, so either set is good terminology or they just are agreeing to make me stop talking.

Heady stuff. :exploding_head:

@tjkoyen thank you. I like this idea of taking a “set”. I shall ponder this.

“In a fast corner, you can feel if you flick the wheel, you can almost immediately put the wheel back to center after your input and the kart just floats through the corner in a controlled, unloaded fashion. In a slower corner, you have to build that up more with a bigger, slower input or you risk going over the traction limit and never really getting the kart to dig or set.”


Also, Taking a set sounds like the kart rotating to be “tangent” to the line and down goes the power and out of the corner on line you go. Zoom.

I think that the set you describe is the final act of rotation. In a long corner the set begins in the braking as you rotate slightly under deceleration. The moment when the energy cycle transfer from the rears to the front is when the set is fully baked and the kart finishes rotation.

Your tight flick corner is a rapid rotation that occurs more in the seat of the pants approaching or at apex but same difference. Where you point the nose as the weight settles and throttle comes in sounds like the “set”.

I think you are changing the trajectory here. You are changing the orientation of the kart along the line (while staying on line with your center of mass?)

in cars, that’s basically a 4-wheel slide/drift. the key is to not overdo the flick, and over-rotate/spin the kart.

In shifter similar, from what I have felt. The rotation is greatly aided by front brakes and allows for very slow rate of rotation, if necessary. That being said, I have no relevant car experience.

It’s not a slide or drift though. It’s kept within the rubber and in slip angle.

I’ve found that some drivers struggle with the concept. I’ve found a track walk really can help.

Additionally, articulating it as “yaw” is helpful at times. This works best with adults.

Once the concept of rotation sets in, its really a game changer

Agreed. Yaw makes sense to folks. Its pretty easy to imagine the car "Yaw"ing relative to the driven line.

It would be interesting to have 4 sensors on the corners and one in the center of mass. I suspect that this could illustrate rotation visually, sorta like an AIM gps path map, but with the data of the rectangle of the vehicle overlaid on the line.

Why? Science!

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Wow. I am trying to wrap my head around all of this.

Dom, your explanation seems a little hard to follow and I think some illustrations might help to convey it better.

It sounds like you are trying to relate rate of turning with weight transition and frame twist.

To build on what TJ was saying about slow and fast corners, its sounding like “a quick flick” of the wheel utilizes the twist of the frame to quickly unload and hold up the inside rear tire aided by the high G forces of fast corners. While a “slower input” relies more on mechanical jacking to unload and hold the inside rear up with out the added G’s to twist the frame as much.

In either case, momentum carried through the corner is limited by the traction or “set” the kart takes when the outside rear tire digs into the pavement unloading the inside rear and allowing the kart to rotate without sliding.

I have noticed at my home track in turn 1, a fast banked long left at the end of the longest straight with little or no braking, I can drive it in deep and with a quick input of steering the kart digs in and I rocket out of the corner. On the opposite end in turn 7, a slow tight flat left at the end of a medium straight with hard braking, slow and steady steering inputs seem to allow more of a controlled turning rate as not to overload the outside rear and start to hop. Seemingly holding the set longer.

I imagine how long you are having to hold that set has an affect on the forces applied to the the four corners of the kart during rotation. Fast corners short duration versus slow corners and a longer duration. Too slow of an input for a short duration and you overshoot your trajectory or the kart lacks grip mid corner causing under steer or push. To fast of an input over a long duration and the kart loads up the outside rear too quickly to the limits of grip and you get sliding or hopping.

Am I on the right track here?

I think so. To your point, visual is best. So yeah you are describing rotation and either controlling it (long slow corner) or creating the situation where it happens quickly (eg: chicane) and influencing it as well.

How much we allow the kart to rotate and when is sort of trial and error, I think. We play with different corner exits until we find the “set” that is most hooked up and sensible for the corner.

So what I was trying to do is find a way to articulate this voodoo to someone. I guess the challenge is that I am trying to articulate something that happens invisibly until you start thinking about it.

Then when we start messing around with it on track and you learn how to make it do your bidding sometimes. In the rubber laid down in the braking zones and apex there is a path. In this path, as you brake and then go to power, you can keep the interlock between the rears and the road connected but not locked down. The fronts fully locked down (beware understeer if you chase the front too aggressively with throttle) and you can let the back chase the fronts around ever so slightly to find the set.

Anyways all this becomes apparent as we become more competent and try to get on throttle earlier.

It’s sort of a weird thread. But maybe productive to someone.

Borrowed from @speedcraft . Image shows the rectangle of the vehicle being yawed to allow max power at exit once rotation “sets” and Full power is applied (and down comes wheel).

I think I figured out where you were going at the start. Sounds like you are applying the idea of tire slip angle to the rear. Like in the front, when you turn the wheel the tires try to change the direction of the kart to where you point them, but as the tire rolls it is actually moving laterally as well up to point of loss of grip and plows straight. (a.k.a. Push/Under-steer).

You are saying by going deeper and turning in a little harder the unloaded rear tires will begin to move laterally there by rotating the rear of the kart rather than just following the front. As a result all four wheels are pointing in line with the track at the exit earlier in the corner and can get back on the throttle sooner. Weight then shifts back to the rear and the kart does not bind, because you have already straightened out the steering. “Chuck it in” too hard and you slide or get over-steer. Do it just right and you find the sweet spot where the tires do not break traction and effectively shorten the corner.

I can see how this could be effective in higher horsepower classes. Like shifters with front brakes can turn in late and hard get the kart rotated then hammer the throttle. They drift laterally out of the corner even though they are pointed down track.

Yep. Coincidentally I am doing a ton of shifter these days in sim and with the front brakes and the grunt, you can pretty much do whatever you want in terms of
Rotation, assuming there’s rubber down, I suppose.

But yeah, yawing the back going in under braking, but not a slide, and then bringing the back in line with the fronts to power out. It’s not a drift and it’s hooked up the whole time. The interlocking of the rear tires and the track rubber allows this. Otherwise it feels like it this normally would result in wheel spin, slide or just plain ending up falling off the track.

On the x30, similar but obviously less Power and no fronts. But it all still applies, just slightly differently.

I’m getting in a 4 stroke tomorrow. I suspect that in the very low hp kart, subtler still. We shall see. I don’t recall moving the kart around significantly in my rental races. The kart tomorrow will be normal weight and uncaged.

“You are saying by going deeper and turning in a little harder the unloaded rear tires will begin to move laterally there by rotating the rear of the kart rather than just following the front”

Sort of. It’s not a question of overloading the kart though. Going deeper isn’t really it, nor does it require a harder turn in. It does require finding the point past which it becomes too deep or hard, however. I am actually braking less hard than in straight line braking. Here, I carry more momentum into turn, surfing rubber for grip. I don’t have the stickiness of the tire ever “break”. This does deform the tires laterally and they do occasionally make weird slurping/folding noises but they ain’t sliding. It’s fast too.

Oddly Dom, well oddly for me as I’m still very new to the advanced techniques and theories of driving, I understand what you are trying to articulate. I’ve had it explained to me very recently by someone at my local track. I was in the fortunate position of doing my practice sessions last weekend as the only none staff member at the track.
Out of what I assume was sheer boredom, the main instructor took it upon himself to help me out. There are two corners where he instructed me that the quickest way to take them is to come in hot, use throttle control to keep the rear end ‘Loose’ but not sliding. This got the kart to rotate nicely. These two corners were my strongest corners during the race event a few days later.

If you remember, what was the principal thing he said that helped you understand the concept?

On that track of your you will get very good at being able to wrassle momentum into something very flowing and beautiful. There just isn’t room to drive heroically or sloppily.

The main terminology that stuck with me was that the rear would feel ‘Loose’, but wouldn’t be sliding. Truth be told it took about 20-25laps and a day or two away from the kart for it to sink in properly. I guess it just takes me time to digest information like that.

@Bobby I think you have to feel it to absorb it. TJ describes it as reaching out its your arm and grabbing a pole at the apex and swinging yourself around. That is indeed how it can feel in a fast rotation corner. In the long corners with a big energy cycle it’s much slower and more deliberate.

Think of your turn 1. Though you don’t brake there you could easily rotate the back in slightly (not that you would, necessarily).

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