The most interesting tech from the F1 2020 season so far is the Mercedes DAS system. Here’s how it could work.

CREDIT: XPB

On the 2nd day of pre-season testing in Barcelona, Lewis Hamilton was seen pushing and pulling the steering wheel on the straights and in the corners, as shown in the video below. Mercedes are not giving anything away so we can only speculate, but this system could be adjusting the amount of toe on the front wheels to try and maximise grip during cornering.







What is toe?

Available at: https://virtualracingschool.com/academy/iracing-career-guide/setups/camber-toe/

So why would a team want to dynamically change the front toe? Toe is effectively the angle between the direction the tyres are pointing relative to the direction the vehicle is pointing, when viewed from above.

1) Zero toe means the tyres are both parallel to eachother and to the direction of travel of the racecar

2) Toe in, or positive toe, means the tyres point towards eachother

3) Toe out, or negative toe, means the tyres point away from eachother.

The amount of toe can affect the vehicle’s dynamic behaviour and consequently driving stability as well as tyre wear and temperature.

James Allison, Technical Director at Mercedes F1, did confirm that: ‘We have a system in the car, it’s a novel idea. We’ve got a name for it, it’s called DAS [Dual Axis Steering] if you’re interested, and it just introduces an extra dimension of the steering from the driver that we hope will be useful during the year but precisely how we use it, why we use it, that’s something we will keep to ourselves.’

On a straight

On a straight, you ideally want zero toe, because this reduces the drag of the wheels and minimises wear. Whenever you introduce either positive or negative toe, the tyres are then travelling at an angle relative to the direction of travel of the vehicle. This means that the tyres are ‘scrubbing’ and being dragged along the track. Although this wears the tyres this can be used as a tool to generate tyre temperature.

‘To some extent they [could be] changing the toe on the straights. Now, there are some reasons why you might do that, just literal drag. You will go faster with parallel wheels,’ says Rob Taylor, Chief Designer at Haas F1. ‘Scrubbing down the straights inevitably puts energy into the tyre, but [this energy is effectively] taken out of the engine. So if you take [that energy] out of the tyre, and the engine can deliver [that] to the air, then [the car will] go faster. So is it top speed? Is it tyre management? I don’t think it’s top speed, I think its tyre management. So you could do it because you think it will improve your outcome over the life of the tyre, maybe. But what they’re actually trying to achieve, I don’t think we know yet.’

Cornering

During cornering, you need to consider the lateral forces that load up the outside tyre. (Think of when you turn right in your car and your bodyweight shifts left.) Toe in on corner entry can help to steer the loaded outside tyre more, which could increase grip. The flip side is that toe in introduces instability in both cornering and on the straights. This is why F1 cars usually run with a few millimetres of front toe out and rear toe in – because overall you gain more grip from minimising this instability, even though this compromises the car’s rotation at the corner apex.

How the Mercedes DAS system works

The Mercedes W11 dual-axis steering trick could be aiming to:

1) On the straight -> Toe in – Pull the steering wheel

Increase front toe in to straighten the wheels and reduce drag down the straight.

2) Under braking -> Toe out – Push the steering wheel

Increase front toe out which reduces instability and scrubs the tyres; generating tyre temperature.

3) Corner exit -> Toe in – Pull the steering wheel

Increase front toe in to revert to base setup, which will still be a small amount of toe out.

By dynamically changing the front toe, this system could allow Mercedes to run more toe out in the corners, to increase tyre temperature, without suffering the drag penalties on the straights. The next question is is such a system legal? According to the FIA, it is for 2020, however the 2021 rules have been amended to outlaw it for next year.

READ MORE: Technical Analysis of the Mercedes W11

The details of exactly how this system could work are yet to be revealed. It could involve hydraulically actuated pistons within the tie rods, or a mechanical system where the steering rack slides.

Underneath the Mercedes W11 at pre-season testing

What is also interesting is that Mercedes ran the system before lunch, when the track conditions were at their best (rubbered in and higher track temps). Were they testing the system to see whether the scrubbing effect of the changing toe would overheat the tyres? Or did they just want to send the media into a frenzy an hour before both Lewis Hamilton and James Allison were due for a press conference? Or are we all completely wrong and the theory of dynamically changing the toe is just a distraction from what’s actually happening? At the moment, only Mercedes knows but it will be interesting to see if they run the system again during testing and whether it will feature at any of this years races.



