Hopping when exitting corner

My kart always hops when I exit the low-speed corner with little throttle. There is no problem to enter the corner.
Any idea to solve this?

My kart is Birel Art with Rotax Max senior.

Thanks,
Aaron

Hi Aaron,

We are going to need a little more information to diagnose your issue. Hopping occurs when the outside rear tire has exceeded its level of grip, breaks loose from the pavement setting the inside rear tire back down, then biting again lifting the inside rear back up in a vicious cycle.

@tjkoyen is our resident handling guru and will likely want you to answer a few questions.

  1. What is you body type/build?
  2. What is the weight split on your kart with you in it (front to rear)?
  3. What is your setup? Camber, Caster, Toe, Seat, Axel, Ride Height, Tire…etc.
  4. Have you tried a different line through that corner? i.e. backed the corner up, rotate the kart earlier and have a straighter exit when you get back to throttle.
  5. Do you have any on-board video?

Greg is spot on.

Hopping is the tire overloading and releasing grip, then grabbing again. So what you need to do is reduce how much load is going to the outside tire. You’re jacking too much weight to that side and overwhelming the tire.

First you need to make sure your hands are smooth and it isn’t aggressive steering wheel input causing it. If it really is the handling of the kart that is the issue, here are some adjustments to try.

Quick and easy fixes:
Widen rear track by 5mm until it goes away
Narrow front track by 5mm until it goes away
Reduce caster
Raise rear tire pressure 0.5-1psi

If it’s really bad and none of that helps, more extreme changes would be lowering the seat or rear ride height or changing axles.

Typically a hopping condition means you’re just over the limit of using the full grip of the tire, so if you can reign it in just a bit, you’ll be using the tire to it’s full capabilities and the kart will be pretty quick.

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  1. I am 165Cm/80KG
  2. I don’t know. My mechanic help me with it. My seat position might my a little foward because I ma short-legged and I have to make me driving comfortly.
  3. I am new to karting, so I haven’t adjust them. They are all Birel default except the rear track width
  4. I will try this because I found it always happens when I apply initial throttle.
  5. I haven’t buy my gopro. I will upload it when I have it.

Thanks,
Aaron

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I go karting only in one circuit because I am just getting familiar with it. When I started karting, I came up to hopping when “entering” the T1 of the circuit, which is a high speed corner. I increased my rear track width to maximum and all the problems were gone.

As I am getting familiar with my kart and my corner speed is higher now, hopping happens again on another low-speed corner when I “exit” the corner. So I can’t figure it out if it is caused by my bad driving skill.

I will try what you mentioned.

Thank,
Aaron

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It can be very common to have hopping or other handling issues as a newbie, stemming from driving. Obviously fixing the driving will help those problems, but sometimes a little change in the chassis can make it more comfortable and easier for a newbie to build up their pace.

The hopping is not limited to a specific corner? It is across all corners when accelerating?

Where does the hop begin in the turn? Entry, mid corner, exit?

Reason I ask is you also indicate that you are new to karting.

Hopping can be a function of asking too much of the kart laterally. Basically sending it in too fast (but not fast enough you slide) can cause the chassis to get overloaded mid corner and it hops to let off load as the load becomes too much.

So I have experienced bad hopping and was able to deal with it by taking a rounder, less aggressive line.

If you are hopping everywhere, that would be unusual. It could be setup.

However, given you are new, it may be driving related.

Only at one specific low-speed corner when I exit the corner to apply the initial throttle. Other mid-d or high-speed corners are fine to me.

Like TJ said, you may just need to slow down a little more before corner entry. I know it sounds counter-intuitive to drive slower to go faster, but if you think about what is happening when you start to corner, rotate the kart and then back to throttle it becomes more clear about what is happening. For example, if your hop is on exit only after applying throttle, then that is the moment the tires cannot cope with the extra lateral load. If you slow down a little bit more before corner entry, roll through the rotation point then once the kart is more straight lined for apex to exit and you apply throttle there will not be as much lateral load on the tires. As you work out the limit of grip, you can apply the throttle earlier until the sweet spot. Ultimately you will be faster even though it may seem slower at first.

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Depending on how you get on the throttle can really affect this. For instance mashing the throttle vs rolling into it.

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The fact that it’s one corner suggests to me that it’s how you are taking the corner more than setup.

I am curious to see the corner.

Here’s one that gave me such bad hop I hurt my ribs:
image
This is a corner at Orlando Kart Center.

Track Map

Track map on Google earth

A driver’s video clip on this circuit.

I’d try a softer rear axle

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I’d try changing up entry/approach a bit and see if that makes a difference.make the turn less V shaped maybe and more U. Make the loading up of the kart more progressive, slower.

If you can, try to get some footage so we can see what it looks like in your case.

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Tell you something I did once too. Point my GoPro at the tyre so I could see slow mo and understand what it was doing.

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On a BirelART, the axle chart is similar to the OTK, so if it’s hopping a softer axle will likely make it worse. Soft axle is for low grip when trying to get rear bite.

I wouldn’t change axle until you’ve exhausted the other smaller options and made sure your driving is good.

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That corner is fairly long, so you may be getting back to power too early. I’d experiment with letting the kart roll deeper into the corner before getting back on throttle and see if that helps.

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I think so too, because most drivers here don’t change their axles. I will try some driving experimets to see what happens.

Watching the vids I’m inclined to agree. Do some practice runs, concentrate on that corner but sketch the corner on paper first. Make notes how you can do it differently- different line, different braking zones, turn in etc then go out and try what you’ve sketched. When you come in look at the sketch and note what helped and what didn’t.

(From Terence book lol)

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Why is addressing this issue different between 2 stroke and 4 stroke?

I’ve always been told in 4 stroke if your rear end is tight and hopping, you bring the rear tires in. Whereas on a 2 stroke, you would bring them outward.

What gives?