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Tkart magazine

The Expert Advices | How to choose the right hubs for the kart

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14 May 2020

Hubs are accessories which play a particularly important role in karts. First of all, on a practical level, their purpose is to connect the wheels’ rims with the rear axle, and with the stub axle as far as the front end is concerned. Yet, in a context of a vehicle like the kart, which has no suspension, hubs have a crucial role in transmitting the stresses from the wheels to the chassis
Even the material they are made of is important as it affects heat dissipation for the correct management of the tires. With the help of Michele Zampieri, CKR technical director with twenty years of experience in the world of karting, we are going to discover all the secrets of the hubs and the characteristics that are preferred according to the needs of the Kart and driver.

1 What materials are hubs are made of? How do they affect their performance?

Kart’s hubs are mainly made of aluminum, 7075 aluminum alloy (AA7075) and magnesium. These materials have different characteristics amongst them. First of all, the weight of aluminum and AA7075 have a decidedly higher specific weight than magnesium. To be precise, we are talking about 2,7 g/cm³ for aluminum and 2,8 g/cm³ for the 7075-aluminum alloy, while magnesium’s value is about 1,73/cm. This parameter is important in karting, where the correct weight management improves the vehicle’s setup since lighter accessories allow you to obtain the correct center of gravity.
Another fundamental difference lies in the thermal conductivity. Amongst these materials, magnesium certainly manages to dissipate heat much better than aluminum and AA75.

Given the lack of suspension, in karts hubs play an important role in transmitting the stresses from the wheels to the chassis

2 Why is thermal conductivity to be considered when choosing the correct hubs?

Magnesium hubs dissipate heat quicker, therefore, in conditions of high atmospheric temperature, this is certainly a positive factor. The hub is in direct contact with the rim, therefore, if it works at lower temperatures, it helps the rim to dissipate the heat generated by the tire. Temperature is important in managing the tires on the track, as a correct pressure ensures better performance. Vice versa, in the case of lower atmospheric temperatures, the use of aluminum hubs may be more suitable which, combined with rims made of the same material, help the tire to reach the optimal operating temperature much faster.

3 Do hubs come in different lengths?

Each kart manufacturer has different hub lengths to choose from. Usually, the standard hub supplied at the time of purchase is the ideal length to make the most of the chassis, on average, in any type of conditions.
As a general indication, we can say that the longer the hubs are, the more they stiffen the kart setup.

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