Kart Hubs: What They Really Do and How to Choose Them
The hub is probably the most underrated component on the whole kart. It is not just the part that holds the wheel on the axle: its length, width, position and even its shape change the stiffness of the axle where it is mounted, and this translates directly into grip and cornering behaviour.
Anyone working on set-up knows about axles, tyres and geometry. The hub is often the last variable considered, when in fact it is one of the cheapest to change for a real effect on track, and in many cases you only need to move it a few millimetres without even replacing it.
In short Hubs affect stiffness and grip more than you might think: in general a longer hub stiffens the axle where it is mounted and increases grip in that area, with a stronger effect on small-diameter axles. Position and wear also matter.
What kart hubs really do
The hub is the cylindrical part mounted on the axle (the steel tube that connects the two rear wheels) to which the wheel is bolted: it transmits rotation from the axle to the wheel. It is not just a mechanical support: it is also a stiffening element. Mounted on an axle, the hub locally stiffens the section of tube it is clamped to. The longer the hub, the less that section of axle flexes.
On narrow-diameter axles (30-40 mm, less common) this effect is very marked: hub length has a direct and clearly noticeable impact on rear grip. On 50 mm diameter axles, the most common in competitive karting, the axle is already very stiff in itself, so changing hub length produces a subtler but still real effect: in this case, as we will see, it is often better to work on hub position or on the axle itself rather than on hub length.
→ Read also: Kart axles: complete guide →
Long or short hubs: what changes
The general rule, both front and rear, is: longer hub, more stiffness where it is mounted, more grip.
At the rear: a longer hub stiffens the axle and tends to make the rear “bite” more into the asphalt. By reducing the part of the axle that works freely between the bearings and the hub, you generally get more rear grip.
At the front: the same principle applies, but with one more warning: too much front grip can make the kart “straight” and reluctant to turn, especially on less powerful karts. In the faster classes longer front hubs are used (roughly 70-80 mm) together with larger-diameter stub axles, precisely because more front grip helps there. An important exception is rain: in the wet it is always worth lengthening the front hubs, in any class, because you need more front grip to make the kart turn when the track does not offer it.
Always remember that these are starting points, not fixed rules: real behaviour also depends on chassis, tyres and track.
Using the hub to correct understeer and oversteer
You do not always need to change the whole hub to correct the kart's behaviour: often it is enough to move it a few millimetres along the axle, changing how much axle is left free to flex between the outer bearing and the inner face of the hub.
If the kart understeers: it struggles to turn and the rear feels too “glued” to the asphalt on entry and mid-corner. By slightly widening the rear track, moving the hubs outwards a few millimetres at a time (roughly 3 mm per side as a first step), the section of axle free to flex increases and the rear frees up.
If the kart oversteers: the rear slides already on entry or mid-corner. By slightly narrowing the rear track, moving the hubs inwards, again a few millimetres at a time, the free section of axle is reduced and rear grip increases.
As a practical reference, which still varies from chassis to chassis: with a 210 mm rear wheel the standard distance between the end of the sprocket carrier and the face of the hub is roughly 133 mm; with a 180 mm wheel, roughly 140 mm. Small deviations from these values, a few millimetres at a time, are the most common way to fine-tune rear behaviour without changing anything else on the kart.
Cutting the axle: the alternative (or complement) to the hub
When hub position alone is not enough, mechanics and experienced drivers work directly on the axle, shortening it by 10 mm or more per side. The principle is the same as hub position, but more effective: the less axle is covered by the hub, the more the force is concentrated on a short section and the more leverage the hub has on the axle. You can also shorten just one side, to correct the kart's behaviour only in corners in one direction.
Manufacturers sell axles of different lengths directly, so you do not need to cut the one you already have.
Material: aluminium or magnesium
Hubs follow the same logic as wheels: aluminium has a greater thermal mass and transfers heat more quickly, so it brings the brake/axle system up to temperature sooner, useful on a cold or wet track. Magnesium, as well as being lighter (so it reduces rotating mass, an advantage for the kart's responsiveness), is also more porous and retains less heat than aluminium: this helps tyre and wheel not to overheat in long sessions, making it preferable in high-grip conditions.
Aluminium is still a valid choice, generally cheaper and more tolerant of impacts.
Hub shape and mounting: details that matter
Not all hubs are the same, even with the same length and material. The side that touches the wheel can be solid and circular, or machined with cut-outs: the solid version bears on more surface and slightly stiffens the wheel-hub assembly more.
The number of clamping screws also matters: a hub with two or three screws clamps the axle over a longer section and is stiffer than one with a single screw.
Finally, some hubs are machined internally along their whole length in contact with the axle, others only in the part near the screw: the latter concentrates the force on a smaller area, a bit like shortening the axle, and changes the perceived stiffness even with the same external hub length.
Wear signs not to ignore
Play on the axle: if the hub is no longer perfectly locked to the axle, you can feel a slight torsional “play”, a sign that the tolerances have widened.
Internal scoring: the inside of the hub in contact with the axle can become scored over time, especially if it is fitted and removed often without proper care.
Cracks near the clamping screws: a critical point to check visually on a regular basis, especially on magnesium hubs after an impact.
Clamping that no longer holds: if the hub's grub screw or clamping screw keeps coming loose even after correct tightening, the hub must be replaced.
Frequently asked questions
Does a longer hub really give more grip?
In general yes, both front and rear: a longer hub locally stiffens the axle where it is mounted, and this increases grip in that area. The effect is more marked on smaller-diameter axles (30-40 mm) than on 50 mm axles, which are already stiff in themselves.
How do you correct understeer or oversteer using the hubs?
By moving the rear hubs a few millimetres along the axle: moving them outwards frees up the rear and helps against understeer, moving them inwards increases rear grip and helps against oversteer. Work in small steps, a few millimetres at a time.
Can you cut the axle instead of changing the hub?
Yes, and it is a technique used by mechanics and experienced drivers: shortening the axle by 5-10 mm per side concentrates the flex on a shorter section, with an effect similar to but stronger than just moving the hub. It can also be done on one side only to correct the kart in corners in one direction.
Aluminium or magnesium hubs: which is better?
Magnesium is lighter, reduces rotating mass and retains less heat, useful in long sessions and high-grip conditions. Aluminium heats up faster, useful on a cold or wet track, and is generally cheaper and more tolerant of impacts.
How often should the hubs be checked?
A visual check before every session, especially after impacts or spins. Also periodically check the play on the axle and the condition of the clamping screws.
Should the hub be changed together with the wheel?
Not necessarily: they are two different components with different functions (the hub works on axle stiffness, the wheel on the tyre), but they should always be considered part of the same system when working on the set-up.
Not sure whether your hubs are still in the right position for your set-up? Message us on WhatsApp and we will help you work it out.
👉 You will find wheel hubs and mounts in our shop: Maranello wheel hubs and mounts.
Conclusion
The hub is probably the cheapest and least considered set-up variable on the whole kart: it changes grip not only through its length, but also through its position on the axle, its material and even its shape. Understanding these mechanisms, together with the axle that supports them, is a skill that makes the difference between someone who just drives and someone who really works on their kart.
Questions about this topic?
Message us on WhatsApp: we answer personally, with the experience of people who live at the track. And if you want to drive a real racing kart, with Arrive & Drive you get into one of ours, ready on track. The right spare part? You will find it in the shop.
Arrive & Drive Pro by TKS RaceLab: 2026 karts with Rotax Senior MAX and DD2 engines, Alfano 7 telemetry and trackside technical support at Lonato, Franciacorta, Cremona and Ala. Message us on WhatsApp for information and availability.
TKS RaceLab | Performance Engineering Karting | tksracelab.com
Read also: Kart axles: complete guide to choice, set-up and replacement → · Kart wheels: complete guide to materials, sizes and choice → · Kart pulling to one side: causes and checks →
📞 Contact
📞 +39 352 0280 133
Author: Sergio, TKS RaceLab | Published: 17 August 2026 | Updated: 8 October 2026
TKS RaceLab is the Italian online store dedicated to karting: spare parts, accessories and everything you need to get on track. With Arrive & Drive you arrive at South Garda Karting (Lonato), Franciacorta, Cremona or Ala and find your kart ready to go. No hassle, just driving.
Comments