Analysis: Is Rake Angle Hurting Mercedes?
- Antony Stott
- Jun 18, 2021
- 4 min read
Updated: Jun 20, 2021
Every year or so in the name of entertainment and car development, Formula 1 regulations are changed. After all if there were no regulations everyone would just be driving around in Adrien Newey's Red Bull X2010 prototype and as cool as that would be I can't imagine the standard of racing would be all that thrilling.
So that's why we have 3 sets of regulations, covering the Racing rules (Sporting), Car design (Technical) and budgets (Financial).
You can find out more about these regulations on the FIA's website by clicking the button below.
In this post, we are focusing on article 3.7.2 of the technical regulations document.
One change for this season has been to the winglets on the rear brake ducts (article 11.5) and changes to the rear diffuser (article 3.7.7 to 3.7.9). While these changes my not be as drastic as alterations such as the switch from V10's to the 2.4L V8's they seem to have had a massive effect on the performance of certain cars. most notably cars running low rake angle.
What is Rake?
If you imagine the floor of the car being level then tilt the floor so the rear is now higher than the front, that's rake!
Every team on the grid is running some rake angle but teams like Red Bull run a higher rake angle than teams like Mercedes, you can see the rake angle highlighted in blue in the images below.
As you can see the rear of the Red Bull is much higher of the ground than the Mercedes.
"Mercedes had high rake last year and they won the championship"
Yes they did, However due to the regulation changes noted above the ability for cars to manipulate airflow with the floor has been drastically reduced. The 2020 cars had several "up stands" on the rear off the floor to aid airflow around the rear wheels which help contain a pocket of low pressure air under the car created by the diffuser.
This low pressure pocket of air is created by the diffuser using what is known as the Venturi effect.
For those unfamiliar with this I would recommend watching this excellent video from khanacademymedicine.
The basic principle is faster flowing air has a lower pressure than slower flowing air.
Because the rear of the car is that much higher than the front of the car this allows more air to flow out this then forces the air flowing under the much narrower part of the floor to speed up to fill in the gaps. This creates an area of low pressure sucking the car to the floor.
In previous years designers could manipulate the airflow using the floor to create barriers of air along the side of the car that keep this pocket of low pressure from escaping out of the sides essentially doing with air what Colin Chapman did with side skirts on the ground breaking Lotus 79.
So why does this seem to effecting Mercedes?
It all comes down to cornering speeds.
Let's look at the Baku GP, this is a great track - in my opinion the best on the calendar - and has produced some amazing races over the years, remember 2017?
What makes Baku so exciting is the mix of high and low speed corners along with the fastest straight of the current batch of F1 tracks, with speeds above 300 km/h.
We all know what happened in the race but for now we are going to focus on the final practice session of the weekend. During this session Mercedes opted to run a different wider rear wing with a steeper angle, this wing produces more downforce at the cost of straight line speed compared to the standard wing. This wing would negate what is called diffuser stall essentially the diffuser stops producing the sucking force necessary to corner faster.
By running a higher rake angle Red Bull can basically extend the length of the diffuser creating a larger pocket of low pressure air and therefore be able to corner faster, higher rake angle also opens up the door for other setup changes like softer suspension as the rear of the car can move down more.
In an ideal world your suspension would allow the rear of the car to be level with the front when speeding down the straights reducing drag and pop back up to produce downforce when cornering, however I'm not sure the FIA would particularly enjoy cars bouncing around the circuit.
As we can see from the best sector times the Red Bulls of Perez and Verstappen are 1st and 2nd respectively with the Mercedes of Hamilton and Bottas down in 11th and 16th, with the Verstappen being 3 tenths faster than Hamilton through sector 1 and 6 tenths faster through sector 2, we can also see the faster cornering speed of the Red Bull in effect here, as well as the ability to get on the power on corner exit quicker. Both of these are aided by the diffusers ground effect.
The same thing can be seen from the results of the Monaco GP with Max taking the win, teammate Perez coming home in 4th with Lewis only managing to bag 7 points in 7th and Bottas failing to finish due to a wheel nut failure.
Monaco and Baku are both narrow street circuits so we will have to wait and see if Mercedes lack of cornering speed hurts them in the more conventional tracks if this is the case, and this issue continues; with teams focusing on developing cars to the 2022 regulations. Mercedes will face an uphill struggle to claw their way back into the title race, which will be music to the ears of Max Verstappen who will hope to finally be crowned champion of the world.
Let's hope Mercedes and Red Bull carry the battle to the final race in Dubai and we can have a final showdown akin to the end of the 1976 season.
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