Steering wheels: tech guide

Date: 29.01.2015

Steering wheels

Austin Allegro Interior with Quartic steering wheel

1958 Cadillac steering wheel

Porsche 356 Speedster

Edsel Teletouch wheel from 1957 demonstrates that wheel-mounted gear shifters aren't anything new

Porsche's PDK double-clutch system remains the gold standard of production car wheel-mounted shifting

Mercedes SL gullwing boasted a 17-inch wheel

Ferrari 458 Speciale's wheel offers a hint of contemporary motorsport

Mark Webber's wheel from the Porsche 919 Hybrid

Mark Webber's wheel from the Porsche 919 Hybrid

Steering wheels

Austin Allegro Interior with Quartic steering wheel

1958 Cadillac steering wheel

Porsche 356 Speedster

Edsel Teletouch wheel from 1957 demonstrates that wheel-mounted gear shifters aren't anything new

Porsche's PDK double-clutch system remains the gold standard of production car wheel-mounted shifting

Mercedes SL gullwing boasted a 17-inch wheel

Ferrari 458 Speciale's wheel offers a hint of contemporary motorsport

Mark Webber's wheel from the Porsche 919 Hybrid

Mark Webber's wheel from the Porsche 919 Hybrid

From crude tillers to carbon fibre tech-fests, we look at the development of the steering wheel...

Steering wheels

Steering wheels

A wheel has been used to aim cars since almost the dawn of motoring: very early vehicles used a tiller a bit like a boat, but as steering mechanisms moved on from a centrally-pivoting solid front axle, steering wheels became more common.

As tyres grew wider, so did the steering wheels as the effort required to turn them, especially at slow speed, increased. Then the advent of power-assistance reduced the work. Some early cars had levers for ignition advance and mixture control on the steering wheel but once mixture and spark became automated, about all that was on the wheel was a horn ring.

Rims got fatter and diameters shrunk; buttons to control functions like the sound system and cruise control were added, as were airbags. There are people who think an airbag is a soft doona that pops out to cuddle you if you’re silly enough to have a little oopsie; in fact, it’s a coarse, artificial fabric sack that explodes in your face – but that’s a yarn for another yard - let’s not scare the horses…

The world has moved on: power-assistance now involves efficient on-demand motors rather than constantly-running pumps. Assistance increases as speed drops: at parking speeds it’s most help, but on the freeway it drops to almost zero. The wheel itself buzzes if the car decides you’re dozing off or wandering out of your lane, and heated wheels help arthritic hands keep a grip.

Steering wheels in racing cars have progressed to carbon-fibre oblongs with brightly coloured knobs, lights and a small computer screen, costing tens of thousands of dollars. In Formula 1, each wheel – and each button’s position – is tailor-made to suit individual drivers.

It’s fair to say that aiming the car seems the most trivial task expected of the steering wheel in Porsche’s 919 Hybrid racer. Drivers of the Le Mans prototypes in the World Endurance Championship operate 24 buttons and switches on the front and six paddles on the back of their wheels, to control the most complex Porsche ever built. 

Although it is called a steering wheel, it’s not round – it’s more of a rectangular plate, thanks to the space needed during driver changes. Tall drivers like Mark Webber wouldn’t otherwise get their long legs in and out of the car quickly. There’s a large screen in the centre of the wheel which displays information such as speed, gear position, engine management map and the status of the lithium ion battery – that is, how much electrical energy is available to drive the front axle. The electric motor on the front axle supplements the turbocharged two-litre, four-cylinder engine which drives the rear wheels.

A rotating wheel at the top left is used to select displayed information and the button in the right grip handle dims the display brightness at night. An identical button in the left grip controls the volume of the pit radio, and the fourth rotary-type control at the top right varies the interval of the windscreen wiper. 

After consultation with the drivers of each car, the buttons are placed to suit them. The most often used buttons sit along the top outside edge, easily reached with a thumb. The blue button at the top right is most used – it’s the headlamp flasher, used by the fast prototypes to warn slower vehicles they are being lapped. One push causes the headlamps to flash three times. In daylight, the drivers keep their thumb on it almost permanently. 

The red button at top left is also used often: it delivers a boost of power from the battery. The drivers can boost to pass but must ration power, as the amount of energy allowed per lap is restricted. The yardstick is one lap of Le Mans, where six megajoules are available and pro-rata for shorter circuits. Energy used in the middle of a lap to get free of traffic won’t be available on the straight.
 
The plus and minus switches adjust front and rear traction control and distribute brake bias front to rear. The orange buttons operate the drinks system (left) and put the transmission in neutral (right).

The red buttons are for the windscreen washer (bottom left), and pit lane speed limiter (bottom right).

At the top the green buttons are for radio communication (left) and the ‘OK’ button on the right, to confirm a setting change, requested via radio, has been performed. To make these changes, drivers use the rotary switches and usually only on the straights, as they need to take one hand out of the wheel grip to do so. 

There are two rotary ‘Multi’ switches: the left one makes ABC settings, the right one is numerical. Engine or fuel management maps are alpha-numeric, nominated and coded as A2 or B3 for example. The other rotary switches select brake balance, set traction control for wet or dry conditions and alter the hybrid strategy. To make the switches easier to use in the dark, their colours fluoresce under an ultraviolet lamp mounted above the driver’s helmet. 

The wheel is made of carbon and the grip handles are covered in non-slip rubber. There are six paddles on the back; the centre ones are for changing gears – pulling the right paddle upshifts, the left one downshifts. The bottom paddles both operate the clutch - depending on whether the car is in a right or left curve, either can be used. The top-left paddle operates the boost; whether the driver uses this paddle or the boost-button on the front is a matter of choice. The top right paddle harvests kinetic energy; it feels like a slightly engaged handbrake and recharges the battery.

Racing drivers operate these complex controls at over 300km/h – no wonder they’re paid huge sums: most people can’t drive and use a mobile phone without slowing down, speeding up or wandering off-course.

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