Downforce/Rake

[TerrorTurtle46™]

Can someone explain me why rake is good? For example you're running front ride height at 55mm and rear at 62... You got a lot of downforce. Why would you raise the rear to create rake? Is this good for tracks with a lot of straights?

[Captain Barracuda]

It's not always good, depends on the car and track. Firstly it increases wing angles. On a lot of the cars there's no other way to dial in extra front splitter angle so rake can be used in conjunction with a slightly reduced rear wing to retain aero balance. It also increases the diffuser angle which can be beneficial up to a point - it also increases the height of the diffuser and the higher the diffuser the lower it's efficiency so there's kind of a balancing act to find here. Increased rake will also assist in rotation of the car and weight transfer to the front - again another balancing act :D Also too much angle on any wing/splitter/diffuser can cause it to stall which isn't good. Centre of gravity at the rear is another consideration when adding rake.

So yer, not a simple answer but hopefully some detail to ponder. There's a lot more that goes on scientifically when rake is increased (pressure zones etc) which are beyond my understanding. Good luck!

[TerrorTurtle46™]

What about the front aero variaton. Do you want to keep that close to 0%?

[ling.speed]

Keeping front aero variation close to zero will >in theory< give you a balanced car, but often not in practice actually. So depending on car and type of corner and suspension stiffnes you sometimes want positive variation and sometimes negative. It usually comes down to confidence in the car - don't look at it as what is better for the car but what makes you drive better.

The lower you go on front suspension the more sensitive the aero will be. With soft suspension and minimal front ride height even if says 0% variation in setup you'll find yourself with like +6% (oversteer) during braking and -3% (understeer) on acceleration in high speed corners anyways.

edit: Ah also many cars also ride on bumpstops at higher speeds and that makes front variation speed sensitive too, so what you set in garage may not reflect the actual variation at speed even when not accelerating or braking. So really no point in striving for some fixed variance value.

Also mechanical balance plays into this as well, as front downforce is almost free drag wise, on some tracks you can crank the variation up and compensate the car balance with roll bars to have good downforce and top speed but bad medium-low speed cornering. While others tracks might need the opposite of that.

Do note that even for tracks with long straights to post best times you still usually want a fair bit of downforce (moderate rake and wing). If you can push the car hard enough to have a use of it that is. The real reason to strip as much wing as possible is to keep you safe in race from overtakes and for endurance reasons as it's hard to push the aero advantage for the whole stint.


And a note on rake - these cars are already tuned to be as efficient as possible, and the range of settings is narrow enough to tweak secondary behaviors. So while more rake = more downforce and more drag, unless you want to make a straight line missile or take all the downforce for a rain race, you kind of set up rake to help suspension tackle the bumps/kerbs with keeping the car glued to the track. Too high and aerodynamic balance will be a mess over bumps, too low and suspension/chassis will be a mess over bumps. (Actually it can happen the opposite way too - the setup really is more for fixing issues rather than giving performance).

[Captain Barracuda]

Yeah you don't want to target 0.0 aero balance specifically, it's just a number. Say you find good car balance at -0.2 at a certain track but you're running a bit low. Your instinct could be just to add 1mm ride height front and rear, but in actual fact that could change your aero balance to -0.3 or something else, so that aero balance indicator is useful to tune the car to the same aero balance when changing things like ride height or rear wing while wanting to keep the same balance (another example is if you want to drop rear wing a bit but want to maintain aero balance, it will help you determine how much rear ride height you need to add to maintain the same aero balance with less wing).

[Dr. Death]

Its quite hard to determine what would be a good aero balance without considering the weight distribution vs the downforce distribution at X speed. This is something i've honestly seen only KSP and Automation explicitly tell the player. Obviously KSP isn't the best at cars.
I dont know if ACC added a feature to see weight balance or how it shifts depending on the speed as aero pushes the car harder. However even just having the car balanced between no speed and full downforce isn't what the driver wants, as if a driver has to deal with a weight balance he's uncomfortable with he can use the downforce to shift the center of the car at least at high speeds to something much more easier to work with, but that's going into personal preference.

[rob_every05]

I can give an example, the Reiter.

I tried the aggressive setup at Monza, was equal ride height, understeer was hideous, was hopeless, put a 1 wing on, upped the rear ride height by 5, made the world of difference.

At Monza they will even at times give you a a higher front ride height than rear to hide the rear spoiler it's bonkers.

[dazbolt888]

There’s another factor to add. Using Motec I can see using my current setup that down the straights 0° rake despite having a positive rake in the setup. Take changes all of time depending on track bumps, aero load and suspension stiffness. So to keep a decent amount of front bias rake you may need to stiffen the rear or lower the bump stop range.

[Abu Jaber drives Simucube 2 Pro]

You must think the car as a wing, more rake = the rear is higher and acts as resistance more than the (lower ) front