Different Types of Axles for Go-Kart Racing

Source: KartSpeed Motorsports

An axle's role as a primary component of any four-wheeled vehicle is amplified when it comes to go-karts. With no suspension, the axle becomes a major component as it connects the rear wheels to the overall chassis. Tinkering with the axle can present major changes in grip, balance, and inside rear wheel lift that is caused by chassis flex. 

Furthermore, because many of a kart’s components are dependent on the axle, this means that choosing the right one from the get-go is key to avoid any major overhaul. In helping decide which axle is best for you, here are the different kinds of axles and what they can bring to the table.

Soft Axle

Source: Pinterest

Up first we have the soft axle. Created with a thin sidewall which allows the axle to naturally bend, its composition aids in building grip as well as keeping it. The picture above shows that by letting the inside rear wheel lift off the track, a kart is able to corner whilst carrying tons of speed. This practice is commonplace in grassroot motorsports due to the fact that only a solid rear axle connects both rear wheels; essentially entailing both wheels can only rotate at the same time. However, it becomes a hindrance when the kart needs to corner, hence the need to lift the inside wheel off the ground. Doing so is easier said than done, but having a softer axle can certainly help.

A soft axle is best in tracks with cool temperatures or wet conditions. Rarer cases such as a dusty track or a resurfaced road can also benefit from this change. The similarities in all these scenarios is that they often present a lack of grip. Equipping a softer axle helps generate more grip and keep the kart responsive.

If the driver feels a lack of grip or notices a hint of understeer, a kart that rotates better may be the solution, hence the change to a softer axle.

Cadet classes can benefit from a softer axle as the driver & kart have less overall weight. The lower weight distribution means less chassis flex, which by changing the axle can be mechanically improved.

Hard Axle

Source: Red Bull

On the contrary, even as a soft axle presents newfound grip, a hard axle offers more stability, especially on exit. Featuring a thicker side wall, making it more rigid in the process. Being stiffer than its bendy counterpart, a hard axle is less prone to flexing which keeps the rear end planted. 

A hard axle’s features shine on high-grip and hot temp tracks by preventing the kart from over-rotating or lifting the inside rear too early. In the process, a hard axle can also help control rear-end sliding in high-traction situations. Another point of note is a hard axle’s ability to carry speed upon exit. Having more stability with this kind of axle means the driver can get on the power earlier, aiding in transferring power more efficiently when exiting corners.

Bearing all this in mind, an axle of this kind is best used when the track is rubbered in, or conditions where too much chassis flex can cause the kart to feel unstable or unpredictable. It’s especially effective when the kart feels twitchy or too snappy, as the added stiffness calms down excessive rotation and helps keep the rear end planted. Finally, if you're struggling with oversteer or rear instability, switching to a harder axle can improve traction under power and provide a more controlled, stable feel through corners and on exit.

Medium Axle

Source: Vroom Karting Magazine

While the prospects of both axles are something to consider, it is important to highlight that their usefulness depends on different kinds of extremes. In other words, a soft axle rises to the occasion on cool, low-grip surfaces, while the hard axle outclasses a field should the track contain hot and high grip conditions.

Most chassis manufacturers design their karts around medium axles. This gives drivers and mechanics the most tunability when it comes to changing conditions. If karts were designed around one extreme, it gives less flexibility as the track changes.

A lot of racers will start the race weekend on a medium axle as it’s a neutral setting that should be suitable for all conditions. Rather than adjusting from a medium to either hard or soft axles, mechanics are now shortening the length of axles (1030mm standard) to (1000mm) to act as a halfway adjustment and increase the axle flex.

CONCLUSION

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For beginners and champions alike, and even track guides on the most notorious race tracks out there, Kart Class will be sure to take you from the back of the pack and all the way to the winner’s circle!