Those strange tilts – Camber

Columns: On the technical side
Among the various geometries concerning the set up of any four-wheeled vehicle, there is one that is often mentioned: camber. Let’s see what it is exactly and how it affects kart behavior.

We continue our journey through our knowledge of the different parameters that define the set up of a kart. The latter is quite a difficult topic, especially for those who have little or no experience with the four small wheels – then again, as far as difficulties concerning difficulties in mechanical adjustments karts can only be compared to the most sophisticated single seaters – but, let’s take one thing at a time, it is possible to work through the various things offered to any karting enthusiast who wants to set up his kart, even if he wants to do it by himself, in the best way possible. Looking at the various karts, especially the single seater (Formula 1 included) you can see how the wheels often have a marked inward tilt. To be more explicit, the top is closer to the corresponding part of the wheel on the other side than the part touching the ground is. This characteristic is known as camber.

It interests us if it’s negative

To be more explicit, when the wheels are tilted inwards it is right to speak of negative camber. This is the situation that interests us most, the one that’s really possible on any modern racing vehicle (automotive vehicle). Using a positive camber, in fact, goes back to the early motorcars, when you were almost obliged to use this solution to help steering and because of the suspension system, which were much more rudimental than today’s. Just look at an elderly, but always fascinating, “Bianchina” to see how leaf spring suspension brings about the need to camber wheels outward remarkably. Usually this parameter is quantified in angular degrees, therefore, saying that there is a 5° camber, we intend that each wheel tilt 5° inward. But in karts it’s common to hear talk of millimeters: this because historically speaking measuring and setting up this parameter is done using the usual bars mounted on the spindles (the ones needed also for toe-in) measuring the distance above and below and making the difference. So, it is normal to say that camber is a few millimeters “open below” in order to identify negative angle. But for correct set up, it doesn’t really change all that much. This even if, it is easier nowadays that well equipped teams use systems with laser beam pointer for adjusting both toe- in and camber. Useful tools not only for adjusting camber quicker but also because they make it symmetric on both sides, which is more difficult to get if using a normal metre: for “squaring” set up, in fact, you need more crossed measurements, to check wheel tilt not only respect to the opposite wheel, but also respect to chassis tubes. Therefore, an operation, which is quite simple risks becom- ing more difficult and compromising the right chassis set up.

It doesn’t work as it does on cars

As we were saying earlier, on Formula cars the wheels, which aren’t covered, allow us to see at first sight how they often use camber angles, which are wide. This is for various reasons: first and foremost because modern radial tyres give most yield round corners when they work with great tilt; then because in away this compensates for the outward tilt of the body of the vehicle (roll), which is however accentuated on cars with wheels not covered; and in the end because this type of adjustment offers more stability the same way as though we would increase toe in, but with less forward resistance. That’s how things stand if we are talking about cars.

But, this time, the kart shows its peculiarity, the difference from any other vehicle, showing reaction on increasing camber (don’t forget, in negative), which is practically the opposite to any other vehicle, whether a single seater or not. In fact, increasing camber and opening the wheels more below, half way round the turn road hold is less and not more as happens in single seaters. Obviously we’re talking about the front wheels only seeing that on karts that have an axle on the rear, it doesn’t allow for any rear wheel angular adjustment. Being the drive wheels, camber may occur both with the specific cams on the spindle pins – but in this case we’ll also change caster, maybe without there being any necessity to do so – both using different spindles concerning the reciprocal angle between the pin on which the wheel is placed and the one used for assembling the chassis.

Corner entry directly improved

Independently from the system that we have used for adjusting camber in the way we think best, what are the consequences on our kart? We often hear that increasing camber also corner entry improves: this affirmation in itself is right, ‘sic et simpliciter’, but we shouldn’t take it as gospel without reasoning. To tell the truth, you get the actual effect of camber more halfway round the corner. As already mentioned, when wheels fully resting on ground with more tilt, they offer less hold. A bit as though we had reduced front track. So as though the fore carriage had been “freed”, but without any negative effects concerning this last operation. In fact, if we had removed the shims or however, reduced front track we’d end up with less directionality also in the phase of taking a corner, and overall behaviour it might even be worse because the front internal wheel of the kart doesn’t go down so much (it’s a case of geometry) so it no longer helps in the same way the corresponding uplift of rear internal wheel. The behaviour of the kart could become really be intolerable, even in an exaggerated way considering the “scarce” adjustment carried out. For this reason, several well known “setuppers” prefer to free fore carriage. For these, values like 1 cm of “opening below” are anything but unusual.

Better to start from zero

Now that we’ve seen the effect of camber on set up, let’s see which is the best way to go about it when we want to adjust our kart by working on this parameter. Well, although we may become boring or repetitive, this time too we suggest you start from basic set up, the one that the manufacturer suggests. He’s the one who can really advise us. Perhaps the only thing we’re told is how to adjust things when using different tyres to those mounted by official teams in top-level racing. Seeing that usually amateur drivers and national classes normally mount harder compound tyres, which wear easier as far as camber is concerned, the need to “free” carriage is felt much less, and therefore with it also the need to have much wheel tilt. On the contrary, if we have no idea of what camber to use on our chassis, we start from zero with basic setup, it’s a good idea to do the same with camber. Literally. That is, start from zero degrees, that is, with the wheels perfectly parallel and perpendicular to the ground. Bear in mind that among other things, also the idea of parallelisms also theoretic, because when the kart rests on the ground, and then we get into it, the weight makes the chassis bend and the front wheels end up having a bit of camber. After, we can try to increase it by a few millimeters at a time (or by a notch on the cams), until we get the flow we want half way round a corner without compromising corner entry. And, always remembering that neither will be entirely satisfactory, we’ll prob- ably have to touch up one or more of the other parameters (chassis height, track, toe-in and soon).

If the worst comes to the worst, maximum camber

Logically, also when dealing with camber you find that when con- ditions become extreme, you can get the desired effects by doing the exact opposite to what you’d normally do. In very cold environmental conditions, high camber, for example, causes a smaller area of tyre tread to work, this however, heats up more and could guarantee more grip. Or a crazy chassis could calm down and give better road hold. For example, it happened to me personally, using a chassis that responded well on wet: only that day, in June, the sun was very hot and the track was perfectly dry...Saying that the kart was impossible to drive is putting it mildly: the risk of ending on two wheels didn’t happen only because when it was so jumpy that you risked going off in a tangent and think that perhaps it would have been better to wear a tooth shield. The problem was only solved by bringing camber to extreme values – something like 2 and a half centimeters more below – enough to have to compen- sate for chassis height so as not to let it drag continuously on the asphalt, the problem was solved. Obviously, at this point, it really wasn’t normal to expect front wheel wear to be regular...

Created by: - 11/10/16

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