Rims enormously have an effect on the efficiency of a kart, each by way of lap time and through a complete race. This is because of the truth that their supplies and shapes have an effect on the temperature of the tyres, which in flip instantly and straight impacts the efficiency of the kart. Alberto Viglino, the engineer accountable for analysis and improvement for the Tony Kart Racing Group, explains which OTK rims ought to be utilized in completely different monitor grip circumstances.
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Let’s begin with a “classic” differentiation: rubber monitor or monitor with little grip. What rim ought to be chosen?
The MXL mannequin with the wheel monitor is normally used: this regards a magnesium rim, which lets you hold the temperature of the tyres as homogeneous as potential throughout a race. With very low temperatures and a monitor with little grip, the selection falls on the MXJ mannequin: it’s a rim all the time product of magnesium however made with a special casting course of in comparison with the MXL which lets you increase tyre temperatures. This attribute will increase the pace with which the tread reaches a perfect working temperature, even with significantly chilly asphalt.
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One other “classic” query: what rims do you advocate on moist tracks? Magnesium or aluminium?
The peculiarity of magnesium is its potential to dissipate warmth and, due to this fact, hold the rubber and air contained inside it cooler
Vice versa, aluminium is a cloth that tends to extend the temperature of the air between the tyre and the rim, thereby growing the rubber’s stress and temperature. What, with chilly and rain, helps set off grip on asphalt. With a moist monitor the selection due to this fact falls on the AXP mannequin, the OTK aluminium rim
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OK. However, in sensible phrases, while you get to a monitor, what are the parameters to examine to resolve which rims you must mount?
Properly, if it is raining, as we have simply talked about, select aluminium. That is a simple one. Nevertheless, one dry tracks, probably the most tough decisions is guessing which rims to make use of. The primary parameter to be evaluated is the temperature of the asphalt: excessive values require rims that generate much less grip. Mainly, asphalt at over 40°C could are likely to require magnesium rims.
Nevertheless, one other necessary factor to think about is the situation of the monitor: for instance, if it has been raining in latest days, the monitor is normally not in optimum situation even with excessive asphalt temperatures, and this makes it higher to begin testing the kart with medium grip rims. The identical goes with tracks which can be very slippery as a result of few karts have been on the monitor or, worse, due to wind has introduced sand onto the asphalt.
Having evaluated all this and determined, a priori, which rim to mount, the subsequent step is placing the selection to the take a look at on the monitor. And this usually proves … that we have not understood something!
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What elements present you that you haven’t chosen the appropriate rim?
Along with suggestions from the motive force, a very powerful elements to think about are the visible look of the rubber and the distinction in stress earlier than and after the take a look at. Let’s begin from right here: if, again within the pits, the distinction in stress in comparison with earlier than the take a look at is over 0.25 – 0.30 bar, for magnesium rims, or over 0.30 – 0.35 bar for aluminium rims, which means the kart is slippery. The truth is, tyres slip once they warmth up an excessive amount of. They transmit warmth to the air contained between the rim and the tyre which, in flip, generates a rise in stress. The upper the stress distinction, the extra it tends to imply that the kart slips. Even tread temperature is necessary, however on this case many elements have an effect on it (the axle, sort of seat and its place, and so forth.) and far is dependent upon the kind of rubber used.
Nevertheless, the best factor is to have a look at the surfaces of the tyres: if they’re all dry and little “sticky”, this mainly signifies that the kart slips and, due to this fact, it’s essential to mount rims that generate extra grip. If, then again, the tyres look “greasy” and have a darker color, the grip ought to be appropriate. The final risk is that the tyres are ruined solely on the entrance or solely on the rear: which means the kart is unbalanced, however, on this case, the issue, greater than the edges, needs to be resolved by engaged on different parts of the chassis (axle , hubs, camber and caster settings, and so forth.).
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What number of rim fashions are there within the OTK vary? And what are the principle variations between them? – “magnesium kart wheels”
There are 4 several types of rims for single-speed and KZ karts:
MXC: it’s the oldest mannequin within the product vary. They’re product of magnesium.
MXL: additionally product of magnesium, they differ from the MXC mannequin solely in relation to the profile, designed to cut back the quantity of air between the rim and the rubber.
MXJ: additionally a magnesium rim. As talked about earlier than, it’s made with a special course of, known as the “near melted” course of. The usage of these rims is really useful in case of low temperatures, or with forms of onerous tyres, since their attribute is to shortly attain excessive temperatures, permitting the rubber to shortly attain the tight temperature and provides most grip.