Why Is the Track Banked So Steeply? Physics Holding the Riders Up

A rider turning a corner needs a force pushing them towards the centre of the turn, and on flat ground that force comes entirely from friction between tyre and surface, which is limited and fails suddenly when exceeded. Tilting the surface lets the normal force from the track itself supply part or all of it, since a banked surface pushes perpendicular to itself and that push has a horizontal component pointing inwards. At the design speed the banking supplies exactly the required force and the rider needs no friction at all to hold the line, which is why the bicycle can be leaned into the turn and feel as though it is travelling straight. The angle needed rises with speed and falls with the radius of the turn.

Designing one balances several requirements at once:

• •A standard length, with 250 metres now used for international competition
• •Banking of around forty two to forty five degrees in the turns
• •Around twelve to thirteen degrees along the straights
• •A smooth transition between the two, since an abrupt change unsettles a bicycle
• •A surface of laminated timber indoors, laid in strips following the curve
• •Marked lines dividing the track into lanes with specific tactical meanings

The markings are not decorative and knowing them makes the racing legible. A black line near the inside marks the measured distance of the track, which is the shortest legal route and the one record attempts follow. A red line above it marks the sprinters' lane, and a rider leading inside it may not be forced out of it, which makes the lane a defended position in the closing metres. A blue line higher up marks where riders shelter when not racing and where a rider dropping back goes. The banking above that is used for gathering speed before a descent into the racing line, which is why riders climb before attacking. Positions on the banking are therefore tactical rather than arbitrary.

The events run on these tracks are unusually varied and several have no equivalent on the road. Sprints are contested between two or three riders over the final two hundred metres, preceded by extraordinarily slow manoeuvring in which riders may come to a complete standstill balanced in place, because neither wants to lead into the wind. Pursuits start riders on opposite sides and measure whether the gap closes. Timed events against the clock include the hour record, which is a rider alone for sixty minutes. Bunch races include one where points are awarded at intervals rather than only at the finish, and another where riders are eliminated one at a time. A two-rider relay in which partners hand each other forward by the arm is the most chaotic to watch.

Machines used on these tracks lack equipment that seems essential and the absences are all deliberate. There are no brakes, because a rider stopping abruptly in a tight bunch travelling at sixty kilometres an hour would cause a crash behind them, so speed is controlled by resistance and by riding up the banking. There is one fixed gear with no freewheel, so the pedals turn whenever the wheels do, which means a rider can slow by resisting the pedals and can never coast. The frames are stiff and the geometry is steep, since comfort and stability over rough ground are irrelevant. Wheels are deep or solid for aerodynamic advantage, which would be dangerous in crosswinds outdoors and is not a problem indoors.

Banking lets the track surface itself supply the inward force a turn requires, so at the design speed a rider needs no grip to hold the line, which is why the angles reach forty five degrees. Standard tracks are 250 metres with smooth transitions between turn and straight. The marked lines define defended tactical positions, and the bicycles have no brakes and a single fixed gear for reasons of safety in a bunch.