McLaren MP4-31 Honda

[DiogoBrand]

Maybe you have answered your own question?
Maybe the slowest cars (most underpowered- Honda and Renault) have to push harder for rake because it is extra down force without the drag?

More powerful engined cars can afford to run 'draggy downforce'?

Force India is also mentioned as one of the teams running a higher rake angle and having a speed deficit.

[CjC]

I have no idea then

[tuj]

Rake is a way of keeping the diffusor working when the aero loads are high. The diffusors are currently too small and on the straights, they stall, promoting even more drag if the stall is not actively managed. I believe the RBR cars trade off the stalling diffusor at high speeds for better handling in high-speed corners.

[misterbeam]

I think most of the teams running high rake want to improve traction by running soft rear, so i guess they calculate that in a way that at very high speeds they get the same ride heights as the other teams running "normal" rake.

[wesley123]

I think most of the teams running high rake want to improve traction by running soft rear, so i guess they calculate that in a way that at very high speeds they get the same ride heights as the other teams running "normal" rake.

This. I too believe that the higher rake is used to run a softer rear suspension rather than to create more downforce.

The issue of a higher rake is that sealing the underside becomes much more difficult due to the higher ride height.

[GoranF1]

Boulier confirms new aero package and software changes to PU.

http://m.crash.net/f1/news/228424/1/bou ... ntial.html

[mrluke]

I think most of the teams running high rake want to improve traction by running soft rear, so i guess they calculate that in a way that at very high speeds they get the same ride heights as the other teams running "normal" rake.

This. I too believe that the higher rake is used to run a softer rear suspension rather than to create more downforce.

The issue of a higher rake is that sealing the underside becomes much more difficult due to the higher ride height.

This would be a massive change for Mclaren as they have run a very very stiff car for a long time now.

[tuj]

I disagree with the idea that the rear ride height in rake is because the teams want soft suspension for mechanical grip. This I doubt very much, because the cars are rarely going slow enough for mechanical grip not to be superseded by the importance of aero.

If you doubt aero works at slow speeds, look at FSAE or better A-Mod autocross cars. They run ENORMOUS wings in A-mod, and it works. So if you have a good diffusor design, you can run the ride height higher to maximize your volume at a specific speed, usually somewhere around the medium-speed apex-speed for the track.

While I do agree that softer suspension; all things being equal, will generally increase rear traction, that is not the reason, IMHO, they are running so much rake.

[Blackout]

I think most of the teams running high rake want to improve traction by running soft rear, so i guess they calculate that in a way that at very high speeds they get the same ride heights as the other teams running "normal" rake.

This. I too believe that the higher rake is used to run a softer rear suspension rather than to create more downforce.

The issue of a higher rake is that sealing the underside becomes much more difficult due to the higher ride height.

"sealing the underside" is bullshit. you keep repeating that, despite the fact other posters proved it's BS.

[misterbeam]

I disagree with the idea that the rear ride height in rake is because the teams want soft suspension for mechanical grip. This I doubt very much, because the cars are rarely going slow enough for mechanical grip not to be superseded by the importance of aero.

These high/low rake designs are not just a matter of increasing height but the whole car is designed around that. What makes me think that it could be traction driven, is that during Singapore 2015, some teams that used normal rake on other tracks, switched also to high rake configuration (like Ferrari).

I also noticed that teams who run high rake usually use "advanced" front wing designs and tighter rear (to be verified), FOrce India tried it mid season too and they are running high rake this year.

[wesley123]

I think most of the teams running high rake want to improve traction by running soft rear, so i guess they calculate that in a way that at very high speeds they get the same ride heights as the other teams running "normal" rake.

This. I too believe that the higher rake is used to run a softer rear suspension rather than to create more downforce.

The issue of a higher rake is that sealing the underside becomes much more difficult due to the higher ride height.

"sealing the underside" is bullshit. you keep repeating that, despite the fact other posters proved it's BS.

Must have missed that, could you link it?

But to get on the "bullshit" part. I thought that air flowing in from the side would reduce underbody performance(ie LMPs used a small lip to prevent air leaking in.) and the ground effect cars used skirts.)

Together with the outward movement of the bargeboard, the lip on the edge of the floor to me it's looks like vortices are being shed in that area to prevent air from the front wheel going under the floor.

[DiogoBrand]

Someone please correct me if I'm wrong (and they are sure of it), but here's what I always (thought I) knew about rake.

Rake is a way of increasing downforce (both for the floor, which is gonna work like a diffuser, and the front wing, that will be closer to te ground) with a smaller penalty on drag than increased wing angles, for example, but it's not every car that's gonna work with a high rake angle because:

a) You need a good aerodynamic seal around the edges of the floor, therefore you need a car designed to work with that rake without too much air leaking in and/or the floor stalling, and

b) You need a compromise in rear suspension setup; in other words, you need a stiffer rear suspension because you don't want the car to change it's height or rolling too much in order not to let the floor stall. Basically, you compromise suspension to gain on aero, which is 99% of the time the way of Formula One, and not the other way around, like some people tried to argue.

[tuj]

It used to be the case that you could control 'heave' through the 3rd member heave-damper and spring. However these have been disregarded at both the front and the rear of the car in favor of 2-member torsion springs and rotary or similar dampers. My point being, the suspension is dominantly setup for the aero package. The suspension must provide a steady aero map for the driver. The J-damper and the FRICS systems were additional ways of stabilizing the aero platform.

I agree rake is a function of the diffusor design. The reason you may have seen some teams running more rake at Singapore last year is that to *some* extent, raising the diffusor increases its efficiency, until it reaches such speed that the rear suspension compresses and chokes/stalls it, or the simple volume of air becomes too much for the diffusor.

[trinidefender]

It used to be the case that you could control 'heave' through the 3rd member heave-damper and spring. However these have been disregarded at both the front and the rear of the car in favor of 2-member torsion springs and rotary or similar dampers. My point being, the suspension is dominantly setup for the aero package. The suspension must provide a steady aero map for the driver. The J-damper and the FRICS systems were additional ways of stabilizing the aero platform.

I agree rake is a function of the diffusor design. The reason you may have seen some teams running more rake at Singapore last year is that to *some* extent, raising the diffusor increases its efficiency, until it reaches such speed that the rear suspension compresses and chokes/stalls it, or the simple volume of air becomes too much for the diffusor.

Different teams have different suspension designs and through pictures it is pretty clear that teams are still using heave springs in addition to others to control squat and dive I.e. ride height.

If you go look at my post in the RB-12 thread I have linked an article written by Willem Toet which explains things such as diffuser angle vs ride height and rake. Very informative and written by somebody who actually is an f1 aerodynamicist.

[bill shoe]

I'll throw a general point in--

The crude assumption is that suspension optimization occurs along a single dimension: soft suspension is good for optimizing performance in the absence of downforce, and hard suspension is good for maximizing downforce. Therefore setup is a simple compromise between the two, mostly in favor of aero because we all know F1 is aero-dominated formula.

Better assumption is to realize that both situations (non-downforce and with-downforce) call for good energy dissipation from the suspension. If you go too hard you simply start bouncing the car up and down on its undamped tires. This is bad for overall quantity of aero-downforce and terrible for consistency of aero-downforce. Worst case is aero-load instability (flutter) and now your driver has a bad headache not to mention a terror of attacking that difficult high-speed sweeper...

Good aero downforce requires good platform stability which requires good ability to dissipate energy from the tires/suspension, and this requires a certain degree of suspension movement between corner and chassis because that's where the damper is.

Suspension needs with aero-downforce are more complex than non-downforce needs, but they are not really opposite to each other.

I humbly suggest this is appropriate for the McLaren car thread because on visual evidence McLaren went for many recent years with suspension that was hardest in the pitlane (worst for energy dissipation). There is also evidence that "Peter Prodromou the aero guy" has advocated better/softer suspension to improve aero performance.