CRG JUNIOR 100CC Guide de dépannage télécharger pdf (Page 4)

Advanced Techniques and Theory

General Theory

To enable us to properly set up a kart chassis, we must first understand the most basic principals of the

racing kart, which is a unit made up of tubes and front steering geometry, propelled through a live axle

(one without a differential). Making adjustments to enable the race kart to turn without oversteer or

understeer is difficult and challenging. Achieving a well-balanced chassis set up is part art and part

science.

Kart racing chassis are designed in a manner to allow it to turn the only way it can, without having a

read differential – with the inside rear tire lifting off the track on corner entry. The outer rear tire drives

“around” the outer front tire, allowing the chassis to efficiently turn into the corner because the rear tire

is off the track surface.

If the inner tire does not lift, no matter how much you turn the steering wheel, the front of the chassis

wants to keep going straight, creating an understeer or “push” condition.

Note: If the driver is not changing the direction of the kart properly, it is possible he/she is making a well-tuned

kart behave badly. While this guide does not delve into driving techniques, here’s something to make sure you

are on the right track:

Observe where the proper apex (clipping point) is for each turn on the track. When you’re driving, each

time you pass an apex in a corner, you should be starting to smoothly move the steering wheel back to

the center. If you do it properly, you will not have to “hold” the steering on, past the apex of the corner. If

you follow this technique and run out of usable track at the exit of the corner, you may have turned-in too

shallow at entry or your apex was too late. If you follow the technique and have too much usable track at

the exit of the corner, then you may have rotated the kart too hard at entry or your apex is too late in the

corner.

If you are holding the steering past the apex, you are holding the kart down, and you probably need to

work on your corner entry techniques. While this dynamic changes somewhat in shifter karts, the basic

principal still holds true: The kart (and you) should do most of the work (change of direction) early in the

corner, so you can drive smoothly off the corner and not bind the kart down. Before completely changing

your baseline kart set up, be sure the problem isn’t the nut behind the wheel.

When a chassis lifts up the rear wheel properly, then the chassis can pivot and turn. Therefore, the kart

must be set up with sufficient side grip to enable the inner-rear tire to lift upon entry, as it is faster to

drive the kart through the corner than to try and slide through.

Generally, when the chassis elements (axles, torsion bars, hubs, etc…) are on soft settings, the kart

has less grip. As the chassis elements are made more rigid, grip will be increased. However, there are

points of diminishing return where the chassis will get too firm to perform properly.

The modern race kart will typically perform best when the rear width is set as wide as possible and the

front width is as narrow as possible, while still providing a fast, well balanced and stable package. You

cannot simply set the chassis on these min/max settings and hit the track, but this concept will help

create a target for your efforts to tune a happy chassis.

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CRG JUNIOR 100CC Guide de dépannage Page 4