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Track Test Tech | Modify the camber. the track test

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CAMBER

It is one of the three angles, the others being the caster and toe, which can be modified on the front-end. It acts on the angle of incidence between the front tyre tread and the asphalt, causing a change to the footprint of the tread itself, among other things. This greatly affects grip and tyre wear. Chassis manufacturers set an optimum camber value, but the grip, asphalt, tyre, engine, etc. variables make it impossible to obtain a perfect angle in all conditions. That’s why the camber angle is modified.

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What

Check the behaviour of the kart on the track by increasing or decreasing the camber

How

Test 1: camber “closed” or negative, i.e. the upper eccentric journal moved inside. Minimum footprint
Test 2: neutral camber, i.e. central eccentric journal. Maximum footprint

Where

At the Adria Karting Raceway in Adria (RO), Italy

Conditions

Well-kept even surface with good, but not excessive grip after a full race weekend. The test was performed using high-performance tires (specifically, Vega Whites)

Weather
26°C / 79°F
IN THEORY
NEGATIVE CAMBER

The camber angle changes the footprint of the front tyres on the asphalt. This results in a variation in grip. A negative camber will cause an inclined tread relative to the asphalt and shall therefore reduce grip compared to a neutral camber. Note that the camber is set with the driver seated inside the kart, because the driver’s weight causes the C (chassis)-stub axle-rim assembly to flex, reducing the true camber value and, consequently, the footprint of the front tyres.

TYRES AND GRIP

A negative camber angle reduces the footprint of the front tyres and causes a reduction of the grip at the front-end. While this hinders the driver going into bends, it also frees the front-end so that exiting corners is quicker, especially the slower ones.
Precisely because of dynamic cornering, the variable effect of the camber should be noted: if camber angle of the outer wheel in the very first section of the bend remains unaltered, once into the bend the camber of the supporting tyre tends towards a more neutral value, thanks also to the transfer of weight: the footprint increases, thereby increasing grip. During acceleration on exiting bends, the camber once again tends to return to its initial value (typically negative) and thus decreases, reducing both the footprint and grip, thereby freeing the chassis.

THE REAR END

Precisely because of the variable effect of the camber angle during the various phases of a bend, it is extremely counterproductive to start accelerating too early. Indeed, generally speaking, the inner rear wheel will lack grip, while the outside front tyre will have the maximum footprint and, therefore, maximum grip. It is clear that, in this type of situation, during acceleration and a further need for rear grip, the rear-end will tend to slip and the kart will go into heavy oversteer.

NEGATIVE CAMBER
53”320
Set-up
Front width 5 notches
Rear width 140cm
Camber Negative
Caster Neutral
Rear height Low
Front height Neutral
What we expected

With a negative camber and a medium grip on the track, the kart should suffer a slight delay when entering bends due to the reduced footprint. After the first half of the bend, the front-end should gain sufficient grip, while on exit it should be possible to accelerate quite early. It is clear that it is vital not to lose too much entry speed to be able to make the most of the advantages of the negative camber out of the bends.

Driving impressions

As expected, it is necessary to go into bends slightly early, since the front-end doesn’t “get a hold” for a few moments. Progress then becomes good and exiting the bend seems easy, in the sense that the kart is settled and the rear-end doesn’t easily lose grip. Clearly, the delay when entering bends makes it difficult to take the apex of the bend perfectly and pass near to the inside curb, which is critical when trying to record the best lap times.

Analysis

With a negative camber (the blue curve on the engine rev graph) going into bends is not as good. The tendency is to brake more before the kart starts cornering or arriving so fast that it’s impossible to go into the bend at the correct moment, with the front-end sliding sideways and the loss of the ideal racing line around the bend. In fast left-hand bends (point 1), after braking there is an attempt to regain speed, but the front-end loses the racing line and the kart tends to go towards the outside. It is necessary to stop accelerating and the loss of time is evident.
The bend at point 2, on the other hand, is suited to a set-up with a light front-end, because it allows the front wheels to slip slightly and prevents a loss of rear-end grip. It is still necessary to corner early so that the kart goes in straight in the slight chicane that follows.
The next bend (point 3) highlights all the shortcomings of an imprecise front-end due to an overly negative camber. Although throttle-off occurs at exactly the same point as the neutral camber set-up, it is necessary to continue braking until after mid-bend to stay on the right racing line. At that point, the speed is slow and even if acceleration occurs quite quickly and sharply, about a tenth of a second is lost.
At the big right-hand bend (point 4), the racing line is partly lost when going into the corner, the driver tries to accelerate, but the kart moves too far towards the outside and the driver is forced to stop accelerating for a moment.
There is an excessive loss of revs during the bend at point 5 due to the impossibility of cornering at an ideal speed.
It is clear that, with more rubber on the track, having a smaller footprint may actually constitute an advantage.

Tires

It is obvious and logical that reducing the camber (i.e. making it even more negative) results in greater wear of the inner part of the tread. This aspect can also generate long-term difficulties in races by reducing the duration of the tyre itself.
Low wear on the outer part of the tread, which looks almost new, is evident in the picture. The front tyres only use part of the tread and there is more slippage, an effect that does not actually increase internal pressure, but merely overheats the tread surface at the point of contact.

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