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Let’s start studying kart parts which can be varied and changed: Gauges width Tyres: types, misture, pressure Front camber angle Front convergence Front incidence Height from the ground Weights/seat position Axle choice Anti-intrusion bar (And in 125 cc also the braking distribution).
The easiest factor to be regulated,
and one of the most relevant ones, is the gauges width. On the left, there’s the back hub (which can be found also on the front wheels in the 125 cc). On the right there are spacers, in this case they are all put in the internal part, to have a MAX gauges width (even if you cannot see, there aren’t external spacers). It’s usually advisable to tighten
and press together the back one if it slips too much, and vice versa
to widen if it grips too much. The same thing can be done for the
front gauges. If your kart is upper/understeering effect, you can try to act on tyres. Considering that, for one reason or another, we are obliged to use one kind of tyres (usually a hard type), we can act and change pressure. Starting from the pressure advised from the manufacturer, it’s usually a good practice decreasing a bit the pressure of the 2 tyres you want to grip more and increasing the pressure of the other two. If the kart is for example understeering effect we can try to decrease about 0,5 - 0,1 bar the front tyres and increase 0,5 - 0,1 bar the back ones. You have to perform this operation when tyres are cold. Even if you have a lot of freedom
in choosing your tyres, I can recommend you the “soft”
ones (maybe used; second-hand). In fact they give you very good
performances in the first 15-20 laps, a worsening until 30-40 laps
and then a kind of collapse. During first laps you can try to drive
very fast, then after the worsening, you can have a performance
like the performance with “hard” tyres. The best tyres
you can get for your kart depend on the kart itself… if it
has a good grip you can continue with the hard tyres… even
if a better grip is a good thing for every pilot! Maybe avoid kind
of experiments like soft front tyres and hard back tyres…
and other things like that! The convergence regulation is one
of the first steps in facing the kart driving position. Back tyres
are not adjustable and they are still on a convergence absolutely
neutral (0° degrees or 0 mm). This regulation can be done both
measuring in mm or in degrees. Generally, it’s easier considering
mm and then calculating the comparison in degrees, but it’s
not so useful… (in the competition “slang” the
convergence is measured in mm). On the left side: neutral convergence; In the middle: closed convergence; On the right side: open convergence. Now, what to do in order of modifying
the convergence? It’s very easy! Look at the picture below.
Picture 2: that rod allows you to modify the convergence (actually
there’s another rod for the left side too). It’s enough
slackening 2 small screw bolts (pict. 1 and 2) and then turn the
rod to one side instead of to the other one. If the distance increases,
wheels will start closing, vice versa they will start opening. Attention
not to leave in the rod a not enough short pivot – in comparison
with the o-ring (the close up object in the picture n.1): try to
find a balance, leave out the screw a same piece, both from the
right o-ring and from the left one. Finished the work, the small
screw bolts have to be tightened. The small screw bolts to be unscrewed are the gold coloured ones in the picture number 1 (so in the picture they are about 2 cm from the right side) and the other one is similar to the others, but metal coloured in the picture 3. The rod, which has to be turned to change the convergence, has an hexagonal shape and it’s blue in the pictures 1 and 3, while it has a circumference shape and it’s metal coloured in the picture 2. And this is to modify it. When you change the convergence, you have to measure it. It’s important to underline the convergence (except for some rare cases) has to be the same in both sides. To do that, the steering-wheel has to be put in a straight position and then you have two different possibilities: the first one is economical and the second one is correct (as usual!). Correct one: buying specific disks for convergence and camber angle (about 40-80 euro). Economical: using wheels as disks. With this second option you have a slight but existing lost of accuracy. Now you have to disassemble tyres and assemble disks if you are in the first option, or leave the tyres there if you are in the second option. With the steering-wheel exactly straight (as we said before), you have to measure two things: one is the distance between wheels in the front side (close to the nose) and the other one is the distance in the back side (at 180°, where there’s the lateral bumper). These two distances should be very similar one to the other: if they are the same, the camber angle is neutral, if the back one is bigger than the front one, wheels are closed forward, vice versa they are open forward. The difference between these two measures is the convergence in mm. Coming back to what I said before, when put the kart on the ground, wheels will be inclined to close up. So a neutral setting when the kart is on the carriage, it means a slight convergence when the kart is on the ground. So the question is: neutral convergence has the meaning of neutral when the kart is on the carriage or on the ground? The answer is “it doesn’t matter”, the important thing is that you have a clear idea about it. Anyhow, you should usually start from a neutral convergence on the carriage (so a little convergence when the kart is on the ground) and then you have to try it. Then you have to open a bit the front wheels so that you are going to reach a neutral convergence on the ground. And you try. Based on how you feel better and how you feel the kart, use that one as the starting setting. Actually if we want to be precise, the neutral angle is the angle on the ground. Now, why regulating the convergence? Well, let’s suppose there’s a speed bend on the right. What’s going to happen when we start it? All the kart weight will be moved to the external wheels (the left ones) and it’s advantageous these wheels can steer more. Well: the front left wheel, with a little bit of convergence, will be inclined to push toward the internal, so with a good grip. That’s going to happen at least on a track with a lot of grip. I have to underline the convergence will cause a lost in speed, both positive and negative. Anyhow it’s not a big problem, and we don’t have to put a lot of attention on this fact. We can affirm a convergence which is closed forward can help in kart lateral grip. It’s like having a hypothetical front aileron on your kart. It’s very different if the track has not so much grip, because here a closed convergence is not useful. In fact a less weight will be concentrated on the external wheels and they will be inclined to slip. On a slippery or wet track, the external wheels strength is low. So the internal wheel will have a relevant importance. And it’s for this reason the convergence has to be open a bit. So the main concept is the following:
it’s advisable adding an angle to the steering one on the
wheel which has a higher impact (which is more loaded) during the
bend. That’s because the most loaded wheel, since it has the
power of pushing down, it has more grip. And here I have to say I’ve
never operated in relation to the camber angle. And the main reason
is that it’s not so easy to regulate (the spindless has to
be disassembled and some ear-ring/bush have to be assembled with
the hole not centred), even if it’s not impossible to do.
So now I cannot give you so many info, but I promise you to improve
my knowledge about this issue. Anyhow, with “tender”
tyres, the camber angle is not useful and it’s better leaving
it in a neutral position, while it becomes very important with hard
tyres. In fact a kart with hard tyres is inclined to slip laterally
in a very evident way, and this grip problem is responsible of a
certain time lost. Hard tyres, resting on the ground in a flat way
are inclined to slip a lot. Closing a bit the front convergence
can be very useful: the front tyres will be inclined to have a lot
of grip and the internal back tyre will raise more. In this way
you should gain a better bend introduction and a running without
particular slipping. First of all, do you know what we are talking
about?
/-\ ---------- camber angle closed to the top (negative) \-/ ---------- camber angle open to the bottom (positive). The purpose of the camber angle’s
angle is having the main part of the wheel well adherent the ground
(or maybe just one part). Let’s imagine a parabolic bend to
the right: it could be useful having the front left wheel closing
to the top, while the right neutral. The camber angle, otherwise
the convergence, doesn’t have to be distributed in the same
way to the right or to the left. It depends on the track features.
So depending on the number of bends to one side or to the other
one, on the type of bends, etc… Anyhow, without too many problems,
an equal distribution can be done. In the front part it has to be regulated putting some thicknesses in the C, up or under the spindless. In the back part, based on the height where bearings are put and where the axle is inserted. Based on my experience, I cannot say anything about the effects. Anyhow if you lift up the kart, you will load more the external wheels during bends, while pulling it down the weight distribution during bends will be more balanced. So in tracks with a lot of grip,
you should lift up the kart and rely on lateral grip. In tracks
with less grip or in wet tracks, it’s better not to load too
much the external wheel, and so the kart should be more close to
the ground.
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