The wheel and tyres of a kart are much smaller than those used in a normal car. Tyres are mounted on the rim which is on the axle of the kart. Rims are made of magnesium alloy or aluminium. Tyres can support cornering forces in excess of 2 G (20 m/s²), depending on chassis, engine, and motor setup. These tyres are specially designed for fast paced racing. They help you to stay on tracks and around tight corners without going off-track. The figure shows the nomenclature of a kart tyre. When you buy a kart tyre on an international level, the specifications are given in the order of tread width, overall diameter and rim diameter.
There are two types of racing tyres viz. slick and grooved tyres. Slick tyres are used for dry racing and grooved tyres are used for wet/rainy racing.
Slicks
There are various brands of slick racing tyres to choose from which include Dunlop, Vega and Bridgestone to name a few. These kart wheels or tyres are specially designed to make as much contact as possible with the track underneath of you to ensure excellent grip and a precise centre of gravity for the kart. This helps the kart to stick on the track and nail those corners increasing speed. The tread is made of a thin layer of rubber that includes a various amount of compounds that make the tyre have either, really good grip or have a greater resistance to wear. Slick kart tyres come in many different compounds, from very soft (maximum grip) to very hard (amusement and rental karts, less grip but long life span).
Rains
Rain tyres are specially designed to help you race in the rain. Some people hate it, but with the right knowledge and some practice racing in the rain can be just as fun as in the sun. They are grooved and are made of soft compound. They are also narrower than slicks. Not all racing classes allow rain tyres. The grooves in the rain tyres reduce the amount of contact area that a slick tyre would give and therefore help keep you on the track. They are constructed the same way as slicks in the way that they have a compounded rubber tread surface that can again be made for more grip or resistance to wear depending on the compound type.
Tyre Pressures
What is the pressure at which a kart should ideally run? This can be of personal preference to some racers. Generally, on an average day when the track is dry and you have your slicks on, a good pressure to start at is around 14 psi to 16 psi. Once you get out racing on the track your tyres will heat up and the pressure inside will build. Depending on how hot it is outside you can expect the pressure to rise between 1 psi to 3 psi. You can then add or release pressure depending on how you feel out on the track. Some people also split up the pressures and add more on the front kart wheels or tyres and less on the back or visa-versa to improve their cornering. It’s a good habit to start checking your tyres before you go out on the track each time. This ensures your pressures are good and that you don’t have a tyre malfunction like a leak causing a flat tyre.
If you are racing with rain tyres, you may want to increase the pressure by about 1 psi to 5 psi. Once the track dries out though, ensure you change back to slicks, as soon as possible. If you don’t, your rain tyres could get worn out quickly.
Tyre Wear
How do you know when it’s time to change your kart wheels or tyres? If you have been racing for a while, you can feel when your tyres need to be replaced. You won’t feel as smooth through the corners which can affect your speed and you may even feel in less control of the kart because it won’t “stick” to the track as well. A good indicator is the kart tyre itself. On slick tyres and wet/rain tyres there are small holes that indicate how much rubber has been worn off. When these holes get shallow it’s an indication that the rubber has been worn out and you probably have to change tyres.
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Toodles.
Chetan Vengurlekar