Engineering DEAD-ENDS Part 2: Hub-Centre Steering

Motorcycle development never stands still, although maybe recently, it would be more accurate to say that motorcycle electronics development doesn’t stand still; it is very little in the physical architecture of a motorcycle that is likely to change. But it wasn’t always so and one innovation that was tried not only on road bikes but also 500cc Grand Prix bikes was hub-center steering.

- Harry Fisher

Hub-centre steering is characterised by the steering pivot points being inside the hub of the wheel, rather than above the wheel in the headstock as in the traditional layout. Most hub-center arrangements employ a swing arm that extends from the bottom of the engine/frame to the center of the front wheel.

The advantages of using a hub-centre steering system instead of a more conventional fork are that hub-center steering separates the steering, braking, and suspension functions.

With a traditional motorcycle fork the braking forces are put through the suspension, a situation that leads to the suspension being compressed, using up a large amount of suspension travel which makes dealing with bumps and other road irregularities extremely difficult. As the forks dive the steering geometry of the bike also changes making the bike more nervous, and inversely on acceleration becomes lazier. Also, having the steering working through the forks causes problems with ‘stiction’ decreasing the effectiveness of the suspension. The length of the typical motorcycle fork means that they act as large levers about the headstock requiring the forks, the headstock, and the frame to be very robust adding to the bike's weight.