Horrible chassis hop out of certain turns especially tight ones

Hello Everyone

I have a wicked hop of of certain corners. I’ve tried a lot of things and have heard different things about rear ride height, I have been told have the chassis low and also been told have the chassis high. I run Bridgestone YLR rok on my Tonykart, if anyone has any input on which slot I should run in please let me know as well as if you have any more suggestions.

A appreciate it thank you!

PS. When I ran used tyres there was no problem but on new tyres and the track getting really hot in FL the hop has been really bad

Thanks again

Got video? I find that hopping in turns is usually me asking too much of the kart at/approaching apex. Could be setup tho.

For starters, what’s your current setup?

Rear width
Front width
Front bar
Seat placement
Wheel type

If it’s hopping as the track grips up, you are likely transferring too much weight onto the outside tire.

Harder axle would be my first choice. But reducing rear ride height or removing caster and softening the front end also would help. Could also widen the rear track to reduce the kart’s tendency to tip and help it cope with the weight transfer more.

But curious to see what your current setup is.

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Axle type N
Rear width 1200mm
Front width don’t remember off top of my head
Caster and camber are in the most neutral position
Seat is about 3-4 mm from base of frame
Wheel type is Factory MXJ rims with Bridgestone YLR

I appreciate everyone’s input!

Is this a cadet/sportsman kart?

No it’s a full sized chassis I race ROK Sr.

@tjkoyen I realize that’s really short, should I measure with the rims and tyres on or without, as I measured without the rims and tyres on

From rear wheel face to rear wheel face, you should be around 1390mm. That is the standard OTK rear track width setting. Sounds like your are measuring incorrectly.

Yea I think so, I appreciate it, I will remeasure

What role would tire pressure play in this. If your thinking is too much transfer could to low of pressure contribute to this?

While tire pressures could be a contributing factor, it’s hard to use that as an adjustment in this case because typically you’re seeing this kind of hopping when the track is hot and grippy, and you are sort of boxed in on the tire pressure you need to run in this situation to keep the tire from overheating.

If you can definitely attribute a handling issue to a tire overheating or not getting enough temperature, then you can adjust the pressure to fix that. But usually if pressures are too low, you aren’t going to generate enough heat to get the kart to become overstuck. The more common issue is too high of pressure, causing the kart to start sliding over the course of the run. That’s the main thing to look at when considering if pressure is the issue. If the kart handling continues to worsen over the course of a run, then you know the pressures are likely too high, and other adjustments to the chassis may need to be made too. The other issue you see is the driver reporting that the kart “never came in”, in which case you would up the pressures to get the heat up faster. In both these cases, pressures being too low and being too high, the kart has a tendency to slide the front and rear. One case because the tires are too cold, and the other because they are too hot.

I don’t really like to use pressures to tune the weight transfer or mechanical function of loading and unloading in the chassis, because you can easily go outside the tire’s optimum temperature range, and the entire handling of the kart can go to sh*t. For me, pressures are better suited to fine tuning the kart’s consistency over the run. Almost like you put the tire pressures/temps in a different category than your kart’s other tuning adjustments.

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I’m with Yoda @tjkoyen. Always makes sense :metal:t3:

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