Picking Up Rear Tires

So I’m still waiting to get on my first practice session in a lo206 and was hoping if you guys could clarify something to me. I understand that when approaching a turn, you brake in a way to bring the rear tires up. How exactly do you brake to bring the rear tires up and on which turns should you do it on? On all turns or just sharp ones? And is this mainly a concept in 2 stroke karting or can it be done in 4 stroke as well?

Hi Eric. Not quite.

You brake to slow the kart down enough that you can turn in to the corner. Rear wheel lifting is an effect of steering not braking, the kart geometry lifts the inside rear through the karts rotation through its vertical (yaw) axis. It needs to do this because there is no diff on the rear axle.

More Advanced cornering - trail braking - can increase the effect by pitching the weight more diagonally towards the front right during cornering

What @Richard_Jacques said. It’s baked into the design of the kart. It just happens. How quickly you raise and lower the wheel is ultimately controllable, sorta, but not something that needs to be thought deeply about at first. The basics is that a quick throttle out of a tight turn will rapidly lower the wheel. A relatively longer, rounder turn with a progressive throttle on exit will have a less abrupt wheel drop. Think centripetal forces, kinda.

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So the rear tire picking doesnt have any real effect on making you faster?

And also, in low hp karts like lo206, is it better to slow down sooner and get back on the throttle sooner than later, like on 90 degree to 180 degree turns?

Lol it’s a bit of a rabbit hole :joy:

How much Lifting of the rear inside wheel doesn’t make you faster per se, more it slows you down less or more, depending how you drive through the corner.

I’ve never driven 206 but the consensus I get on here is yes you need to be on the gas powering out of the corner well before the apex. If that means sacrifice some entry speed then that’s what you need to do.

Let’s back up and actually explain what’s happening here.

When a 4-wheeled vehicle goes around a corner, the inside wheels have to make a smaller radius than the outside wheels. In most vehicles, there is a differential which allows the rear wheels to turn at different rates, allowing them to rotate the vehicle without scrubbing. A kart does not have a differential, it has a live or solid rear axle. Both wheels are connected. Because of this, they cannot turn at different rates when a kart is turning a corner. So if both rear wheels are on the ground, the inside one will scrub against the track surface and slow you down. The most effective way to alleviate this is to allow the inside rear wheel to lift off the track surface slightly when cornering, eliminating that scrubbing effect.

If a kart is setup properly and the driver is driving properly, the inside rear wheel will lift off the ground when turning. Karts are designed to do this. There isn’t a special technique for it, other than driving smoothly and making chassis tweaks to get it to happen. A kart frame is designed to twist and flex, and has a lot of front end geometry built-in to flex the chassis and lift the inside rear wheel, but if you don’t quite nail the setup or you drive poorly or don’t push the kart to the tire’s limit, it won’t lift as effectively.

All of kart chassis tuning basically comes down to controlling how much inside rear wheel lift you’re getting.

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This is the heart of it. Sometimes you’ll hear the term “bound up” or “tight”. I could be wrong here but that’s often driver. The way they are turning and putting down power is maybe causing the tire to drop too soon and the kart struggles with both tires down too early. You get weird behavior that way and it feels wrong.

Anyways, something to consider if you feel like you aren’t very fluid on the track.

Oh that makes more sense, how would I tune the chassis to lift the inside rear up if it isn’t lifting enough or lifting too much?

There’s a million different ways to increase the amount of inside rear lift on a kart. Almost every topic in the chassis section here pertains to it. Wider front width, more caster, narrower rear width, raising the seat, raising rear ride height etc. etc.

I wouldn’t worry about that just yet because:
A. You won’t be able to tell the difference between a kart that is handling well or poorly in the beginning. You don’t have the experience yet.
B. Your main focus when getting started should be driving, learning the limits of the kart and yourself, and a whole host of other things before diving into tuning.

Set everything at baseline/neutral/medium and once you are turning consistent laps within a second or so of the leaders, then I would start looking at how the kart can be improved with tuning.

I know I’m trying to understand too much even though I haven’t sat in something other than a rental kart, but it’s so fascinating and exciting to learn, I’ll focus on that once I can survive a lap without slamming into walls (just kidding, I’m not THAT bad) :joy:

It is indeed common to want to understand everything. What’s best about that is that trying to understand stuff before you have oractical experience leads to some interesting learning processes.

What you think is happening or should be happening has to feel correct as well. All good karting has a feel to it. You know when you are driving well because the kart stands on its toes and starts to handle. Really handle.

There’s a lot of stuff I intellectualized that in practice was different. I had to unlearn the biases I had created for myself from trying to learn driving in my mind. What I thought I understood wasn’t wrong, it was incomplete, however. But, the excessive thinking about it didn’t hurt, it helped, even if not quite correct. Overthinking can be a problem, but not questioning and trying to understand the how’s and whys, is, to my thinking, a guarantee of slow progress.

In high horsepower karts you will turn sharper at beginning of corner and straighten out more later in corner. This is because in a shifter for example late in corner you are going a lot faster than early in the corner. As a result this means you will typically brake later, turn sharper, and apex later.

In low horsepower karts you will only carry a little more speed on corner exit than on entry. So entry will be a lot less sharp and exit will be more sharp (turned) than shifter. As result you will want to brake earlier and turn in less aggressively and apex sooner.

Who ever told you that? In a turn, if the inside tire is not off the ground, you’ll have trouble turning at all. And if you do turn, that tire is dragging on the ground, slowing you down.
Go into the turn as deep as you can, as straight as you can. At the right moment, start your turn, get back on the gas as soon as you can. If it looks like you may drop a tire coming out of the turn, do not let off the gas, touch the brakes just enough to keep from dropping that tire on the outside. If you flap the throttle, the exhaust temperature goes down, you’re making less horsepower, it takes a moment for the HP to get back up.

Don’t get too focused “lifting” the inside wheel in the literal sense where there’s a visible gap between it and the ground.

Yes, unloading the inside rear is important but you’re not likely to be lifting the wheel up on every turn and it should not be a goal either.

Broadly speaking I’ve found the fastest setups will visibly lift at only the tightest turns. For the rest of the lap, you’ll likely see the tire in contact with the ground, however it’s load is changing dynamically in each turn, along with the scrub.

Oh ok, for some reason I thought that the rear tire picking up was because of the driving style. So I understand that it picks up naturally based on chassis design correct?

I can understand why picking up the rear tire wouldn’t be ideal on all turns, I was mainly wondering about it in terms of when you turn on a hairpin.

I understand that especially in the LO206, keeping momentum is extremely important, due to low HP

Basically, the tighter you make the turn, the more of a “V” you make it, the quicker the inside rear will rise/fall.

The other big par of this is how hard and how soon you get back on the gas. Hitting it hard and early will drop it quicker than slow and long.

But in order to turn faster, wouldn’t you need to ease into the gas that way you don’t drop the rear tire, making it harder to turn?

Sort of depends. In most corners, you want to get the kart rotated before the apex so you are back on the throttle as early as possible. This allows you to hit the apex in more of a straight line and reduce the drag of both rear wheels on the ground while still turning. How hard you apply the throttle depends on your available power and the level of grip you are working with or to some extent the engine package you are using. For example, on a Rotax if you bury the throttle it will bog the engine, but you use a smooth application, it will spool up much easier.

What Greg said. It’s a bit confusing but will become clear on track. Sometimes you need to be quick to throttle, sometimes not.

Bogging, with full throttle, says to me, not enough fuel at that throttle [email protected] that RPM. Richen the low-speed, see if it helps.