What is Mercedes’ DAS system

Everyone knows that in Formula 1 every millisecond counts. With cars getting faster and faster every year, teams have to come up with newer ideas to get better lap times. The past years have seen a lot of new innovations in which the engineers have found a way around the rulebook, be it the six-wheeler Tyrell, Brabham’s Fan car, William’s active suspension or be it Brawn GP’s Double diffuser. The most recent of them being Mercedes’ DAS or the Dual Axis Steering as termed by James Allison, Technical Director of the team.

Recently, during day 2 of the first week of winter testing in the Catalunya circuit in Barcelona, Lewis Hamilton sent the whole F1 community into chaos as he pulled and pushed his steering on a lap around the circuit. The Dual-Axis Steering changes the toe angle of the front wheels. Now, the toe is the angle of the wheels relative to the perfect straightforward direction of the car. So wheels with zero angle of toe point straight up ahead, wheels with positive toe point towards to centerline of the car and wheels with negative toe point away from the centre of the car. Well, now one will think why on earth would you have some offset in the first place. Well like I said every millisecond counts. So every minute detail counts. So let us see what all parameters are affected by toe angles.

The first thing is the tyre wear. Imagine if the vehicle is with zero toe and pointing straight ahead. As you drive the car forward the wheels are just rolling freely on their axes. If the tyres are toed outwards the insides of the wheels are somewhat dragging so the inside part of the wheels wear out earlier. Similarly, the outside of the tyre will drag and cause wear and temperature issues if the tyre is toed in. 

Secondly straight-line speed. Again it will make sense if there is no toe involved whatsoever because if the tyres are toed anyhow it will be like dragging the wheel and it might affect only by a few km/hr but anyone familiar with formula one knows that the small things soon add up.

The third parameter is corner handling. This is the aspect where zero might not be your best friend. Let us think you are turning around a corner and making a right-hand turn. So if you think about it the inner wheel or the right wheels, in this case, will turn more and will have to travel less distance than the left wheel. So the inside tyre is always tracing a tighter curve than the outside curve. So ideally you would want the inside to turn by more angle than the outside tyre. This can be achieved by the toe out-step. Toeing the wheels inwards and taking a turn will make the car more reluctant to turn because when you plant one tyre to the correct angle, you take the other one away from the correct angle, causing drag and resistance at the front end of the car.

Finally, straight-line stability. Like I just mentioned that toe out makes the car absolutely ready to turn. As soon as you start to turn the steering, the wheels if toed out encourage the car to turn. This means that as long as you hold the steering perfectly at the center, the car will move in a straight line but as soon as you turn it slightly the car will want to move in that direction, hence reducing the stability of the car. Conversely, if the wheels are toed in the car will respond more lazily to the steering angle, hence making the car more stable. 

So now, as you can see, it will always be a tradeoff like almost everything else in a race-car. So teams have to decide on the toe angles by simulations and iterations and these settings are different for different tracks. So now, the problem is who do you want to keep happy. What Mercedes has managed to do is to give the drivers the power to adjust toe angles while driving the car by pulling back or pushing forward the steering wheel.

The Dual-Axis Steering system allows the driver to pull back the steering to have a toe in setting and push it forward for a toe out. This has several ramifications. The obvious one being they can straighten up the tyres for the straight to increase their speed and reduce wear while also pushing the toe out at corners to give cornering stability.

The other advantage is that the heat the tyres receive can now be manipulated. If, during a race in Monza with toe in settings, because of those really long straights, Peter Bonnington can simply tell Lewis over the radio that you need to heat those tyres and tell him to switch to the toe out setting.

These small changes in toe angle can result in huge victories because we all know that in F1, small things add up pretty quickly.

Overall, we as fans love it when engineers think out of the box to bring us such great innovations and we can’t wait for the season to get started.

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