The material with which the wheels are produced influences the temperature the tire reaches with its increasing number of laps. Magnesium is more porous than aluminum and has a greater tolerance to heat, therefore, the temperature of the tires is kept on a more constant level. On the other hand, with the aluminum wheels, the temperature rises and there is a consequent increase of air pressure during the course of a race, factors that must be taken into consideration at the inflating process of the tires. Safety screws are mandatory on international competitions and their use is extremely advisable in those situations that utilize air pressure below 13 PSI. Such screws have an un-jumping-off function and are highly recommended, particularly in kart circuits with high-speed turns and where the asphalt has too much rubber. The geometry variation and the wheels’ dimensions also directly influence the performance of the tires.
* Only trained personnel should mount the tires, making use of safety equipment (goggles), and following the necessary precautions. * Never inflate the tire beyond the maximum air pressure recommended by the manufacturer. In case of difficulties to mount a tire, dismount it, start the procedure over, and check if the wheel shows any problem. *Never stay close to a wheel during the inflating process. In case of explosion, wheel fragments may cause injuries. *Make sure that the tires are properly mounted on the wheel after the inflating process, checking for possible leakages. Make use of a neutral soap and verify if air bubbles start to appear, particularly around the valve stem. *Before you test the tire, make sure that there are no cuts, punctures, or rubber anomaly, especially if the tire has been previously used in another race.
Mounting and dismounting kits
It is advisable to purchase some very useful equipment to mount and dismount tires: tire dismounting tool, valve disassembly tool, leather or metallic belt, balancing rack, neutral soap to assist in the mounting, air pressure gauge and, of course, an air pressure pump at your service.
To completely deflate the tire, it is recommended to remove the valve inside the valve assembly with a valve disassembly tool, a small and useful equipment in which the tip has a fitting that is attached to the valve. It is also possible to deflate the inner air simply by pressing the valve and considering the amount of air still inside, but this will take longer. In some wheels, particularly the ones made with magnesium, and used in important competitions, near the outside tread, in the 120° radial position, there are three fixed screws with the function to prevent a jumping-off from the wheel. Such screws are almost indispensable on tracks with extreme high-speed turns or low air pressure tire inflation. Without them, there may occur some deformity on the tire bead with a risk of separating the wheel from the bead. It is necessary to unscrew it almost completely by tensioning, to avoid protuberances that may form inside the wheel channel and prevent any hampering to jump off the tire. Right afterwards, place the bead breaker over the tire sidewall near the wheel rim and press it in several places until the tire bead gets loose. Then, after the wheel is turned to the opposite side on the dismounting equipment, repeat the operation, taking care to avoid any dent on the wheel rims. Press the tread band out, attempting to fold the side of the tire to the back of the inside wall until reaching half-circumference (Fig. 1), with one hand, hold the wheel and fold the tire on the upper part. With the other hand, impel the wheel to get inside the tire (Fig. 2). Afterwards, spin the tire and impel the wheel to get outside using neutral soap on the bead, if required.
For mounting operations, you just have to reverse the dismounting procedure. To re-mount the tire, it is useful to lightly brush a wet soap and pass it on the beads (Fig. 1). Do not make use of any other products, like lubricants or grease. Before you start mounting, check the rotation side of the tire and make sure to put the wheel through the correct part. Then, position the tire with the rotation arrow correctly and place the inner part of the wheel by pressing and spinning it, while the tire is kept without any movement (Fig. 2). At this point, the next step is to put the tire's inside face. This is done by folding the inside wall of the tire and impelling it inwards (Fig. 3). Place the wheel with the inside wall up, hold the wheel and the tire with one hand, and with the other hand impel the tire inwards (Fig. 4). Next, push the tire over the lip of the wheel, place it in the start-up position and inflate with an air pressure greater than the one used for tests, 42 to 56 PSI, at most, to allow a rapid inflation (Fig. 5). It is useful to remove the valve (if it has not been done before) so that after the tire is pushed over the wheel the air may flow out more easily, thus avoiding any deformation to the tire. The core of the tread band, the one that under pressure may originate a deformation, is wrapped in a metallic belt, which has a closing system; or in a tightly closed belt, to avoid any tear of the fabric and enable the approximation of the heels to the bead. This is a very delicate phase due to the not so far-off risk of wheel exploration. Some companies prepare safety packages where the wheel is wrapped during inflation under extreme air pressure, able to withhold fragments of a possible and unwanted explosion. In any event, it is imperative to protect the eyes with plastic goggles and keep the face away from the wheel as much as possible. When the tire is pushed into the wheel, replace the inflating valve and then calibrate the tire according to the air pressure previously indicated for the type of rubber and track conditions.
*Tracks with little adhesion usually require higher calibration. At first, consider to inflate with air pressure between 13 and 15 PSI (hot tire). *However, in circuits with too much rubber on the ground, a situation that is common when there are many karts in the track, it is advisable to use lower calibration (10 a 13 PSI) with hot tires. *Weather changes influence the kart's behavior. *Tires with a softer compound may require calibration lower than the one used in tires with a harder compound. *The air pressure gauge used to measure the tires pressure is an essential piece of equipment among the tools of any kart team. You should invest in an excellent air pressure gauge and avoid tumbles or misemployment to keep it in perfect serviceable conditions.
Karting tires are designed to reach the best performance levels when the tread band works in a temperature ranging between 80 and 95°C (176° and 203°F) degrees. The pyrometer is the most appropriate tool to measure the tires temperature. It is worth noting that the karts set-ups or adaptations in the driving style may determine and help the tires to work at a stable temperature, leading to a performance peak and avoiding untimely wear. The type, conditions of every asphalt, and the features of each circuit also directly influence the temperature reached by the tires.
Balancing of the wheel/tire set is of major importance to reach the best performance of your kart. Unbalanced wheels can cause vibrations, driving discomfort, excessive wear of the tires, and poorer performance. The balancing of a kart wheel is of the static kind, with one wheel standing on a rack, without using a balancing machine. The front wheels can be balanced with the tire assembled on the kart, while the rear wheels need the support of the balancing equipment. The ideal balancing depends on the equilibrium of the set weight and it can be noticed when, after several rotations, the wheel always stops in different positions. Use lead for balancing by degreasing the wheel well before the final fixing.
Deflate completely the tires after a practice or race to avoid deformation caused by the rubber’s high temperature. Very often, the same set of tires is used more than once in a succession of races and such procedure prevents unpleasant surprises or sudden changes in the kart's behavior.