By increasing or decreasing the distance between the outside of the rear axle outer bearings and the inside face of the rear wheel hub you are in fact increasing or decreasing the amount of “working” axle. In other words, the length of axle between the kart’s main chassis rails and the wheel assembly that is left clear to flex unhindered.
In the same way as altering the rear track width, reducing the amount of “working” axle will make the rear bite into the track and sometimes provide more rear grip. Instead of narrowing or widening the rear track, the ability of changing to longer or shorter hubs is a major advantage in trying to obtain the ultimate kart balance. Different length wheel hubs are available and these can be utilized to further fine-tune your kart’s handling.
7.10 (210mm) Wheels – 5.25″ (133mm) from cassette to face of hub. Overall width 54.5″ (138.5cm) from outside wheel to wheel.
6.00 (180mm) Wheels – 5.5″ (140mm) from cassette to face of hub. Overall width 53″ (134cm) from outside wheel to wheel.
When your chassis is OVERSTEERING (loose) in the entry to apex of the corner you should decrease rear width by 1/4″ (6mm) total each session until desired grip is achieved. This will increase the level of grip in the rear and improve the OVERSTEER of the chassis.
When your chassis is UNDERSTEERING due to the rear being too stuck in the entry to apex of the corner, you should increase rear width by 1/4″ (6mm) total each session until desired grip is achieved. This will decrease the grip and improve the UNDERSTEER of the chassis.