The ridiculous downforce values for road cars (?)

  • Thread starter JTB10000
  • 15 comments
  • 4,820 views
1,234
United States
California
JoshsoJB
Edit: uninformed take ahead lol.

This is so silly. According to the car settings, the Renault Mégane Gr.4, just the regular Mégane hot hatch with a little lip, a wing, and a diffuser(?), has more than TWICE the downforce of aero monsters like the LaFerrari, Vulcan, Veneno at the rear? And they have ZERO downforce at the front??? I'm not an expert in car physics but that don't seem right. The Vulcan is practically a Gr.3 car in terms of aero yet has less than 1/3rd of the downforce of the Gr.3 cars at the rear (and, again, absolutely none at the front).

Then there's this oddity: the Mercedes SLR McLaren, basically a wedge with a small active aero spoiler that comes up during braking, has 1.5x the downforce at the rear than the cars mentioned.

WHERE ARE THESE VALUES COMING FROM. Why have most of these cars been nerfed so ridiculously much? A "driving simulator" shouldn't change the foundation of a car just to accomodate the competition. Make the cars accurate and have the balancing systems in place do their thing.
 
Last edited:
2,014
United States
Azle, Texas, USA
GTP_KinLM
KinLM
This is so silly. According to the car settings, the Renault Mégane Gr.4, just the regular Mégane hot hatch with a little lip, a wing, and a diffuser(?), has more than TWICE the downforce of aero monsters like the LaFerrari, Vulcan, Veneno at the rear? And they have ZERO downforce at the front??? I'm not an expert in car physics but that don't seem right. The Vulcan is practically a Gr.3 car in terms of aero yet has less than 1/3rd of the downforce of the Gr.3 cars at the rear (and, again, absolutely none at the front).

Then there's this oddity: the Mercedes SLR McLaren, basically a wedge with a small active aero spoiler that comes up during braking, has 1.5x the downforce at the rear than the cars mentioned.

WHERE ARE THESE VALUES COMING FROM. Why have most of these cars been nerfed so ridiculously much? A "driving simulator" shouldn't change the foundation of a car just to accomodate the competition. Make the cars accurate and have the balancing systems in place do their thing.

I would highly recommend watching Chris Harris’ video on youtube where he compares a McLaren Senna GTR to a normal GT3 McLaren.

I would also recommend his video of the FXX-K in which he cements what I’m about to say.

His comments on the downforce and how it drives are very noteworthy.

In reality, these road cars that we think are “aero monsters” truly aren’t. They don’t have flat floors. They don’t worry about flow separation. They have to worry much more about drag coefficient for emissions regulations.

And 99% of people will never drive them hard enough to know the difference.

They’re mostly there to “look” like they’re aero monsters. Even track monsters like the Senna and Vulcan.

In Harris’s video of the FXX-K, he mentions how it still “feels like a very fast road car” rather than something like an actual GT3 racecar with downforce.

Yet this is a car we all probably consider to be an “aero monster”. Much more so than the normal LaFerrari.

This also explains why the Vulcan has “bad braking” like everybody complains about on here, since that’s mostly limited to tire compound and grip from aerodynamics on cars at this level (which is a thread I’ve wanted to make for a while but haven’t had the time).

I think we genuinely overestimate the aero of road cars, and underestimate the aero of proper race cars. In that regard, GTSport does a very good job of mirroring this line between fast “road cars” with lots of downforce for a road vehicle driven by anybody, and a proper GT racecar designed by top aerodynamicists to have insane downforce, much more intricate diffuser and flat floor designs, and to be driven by people who will actually use that.

Just my 2c

EDIT: I also wouldn’t read into the values listed in the car settings too much. It seems as though there are more underlying factors determining the actual grip and downforce levels of the car than just these two values (underbody downforce, for instance, is not demonstrated here. Nor is/was something like the fan downforce from the Red Bull X cars in past GT games).

Also keep in mind that weight/mass has an effect on how useful downforce is too. So a car weighing 2000kg with 500kg of downforce will benefit roughly half as much as a car weighing 1000kg with 500kg of downforce, *on top of* the fact that the 1000kg car will already drive better due to having half the mass.

(This is another reason why road cars/non race cars generally do not actually produce much downforce; they are so heavy that in order to produce proper, useful downforce, they would need as many wings as a Pikes Peak car. And even if they DO generate lots of downforce, the effect will be much smaller proportionally, compared to the same downforce levels on a lighter, actual racecar.)
 
Last edited:
1,234
United States
California
JoshsoJB
No, you're wrong.

jk I was talking out of my butt honestly. Very informative 👍 The SLR McLaren having a downforce value that high is still kind of weird, comparing it to other cars with similar active aero.
 
624
United States
United States
I think we genuinely overestimate the aero of road cars, and underestimate the aero of proper race cars. In that regard, GTSport does a very good job of mirroring this line between fast “road cars” with lots of downforce for a road vehicle driven by anybody, and a proper GT racecar designed by top aerodynamicists to have insane downforce, much more intricate diffuser and flat floor designs, and to be driven by people who will actually use that.

Just my 2c
Yes, a road car is doing extremely well to simply have an even aero balance, let alone any significant amount of downforce. Even something like the 911 GT3 RS has its downforce figure quoted as 770 lbs at 186 mph (350 kg at 83 m/s) which is not a realistic speed for any sort of cornering. If we assume downforce rises with the square of velocity, in a medium speed corner (say, 80 kph) the car isn't even making 30 kg of downforce. Basically negligible.

A real GT3 car makes about 1000 kg of downforce at 200 kph, for comparison.
 

LeGeNd-1

Premium
6,813
Australia
Australia
GTP_LeGeNd-1
PD aero values has been shown to be messed up for a lot of cars.
- Road going hypercars often lack front downforce leading to severe understeer balance at high speeds.
- Track cars like Vulcan are classified incorrectly and given too little downforce (it should have comparable amount to the P1 GTR and Zonda R for example).
- The McLaren F1 has too much downforce for such an old car with simple aero, which results in it not being able to reach its real life top speed.
- On the other hand, the LaFerrari has too little downforce & drag, which results in ridiculous 400+ km/h top speeds.
- Old race cars like the 330 P4/XJ13/GT40 should barely have any downforce but they have quite a lot.
- Old and new race cars in the same Group has the same downforce values, even though we know they obviously don't from their relative performance (e.g. F1 GTR vs GT3, old vs new Super GT, Group C vs modern LMP).
- Underbody downforce is not accounted enough in most cases. Pitch sensitivity and rake doesn't really affect aero balance as much as it should.

More discussion here:
https://www.gtplanet.net/forum/threads/top-speed-physics.384845/

Also, we never know what those numbers in settings screen represents. The closest would be kg of downforce but even that is not accurate for a lot of cars. Also in real life you do not have 100s of clicks of adjustments like that. In ACC, GT3 cars have maybe 1-3 front splitter levels and around 10 rear wing levels. Even F1 cars, the most aerodynamically complex race cars on the planet probably only has 20-30 wing adjustments max. So either way GT's aero tuning is FUBAR as well.

Yes, a road car is doing extremely well to simply have an even aero balance, let alone any significant amount of downforce. Even something like the 911 GT3 RS has its downforce figure quoted as 770 lbs at 186 mph (350 kg at 83 m/s) which is not a realistic speed for any sort of cornering. If we assume downforce rises with the square of velocity, in a medium speed corner (say, 80 kph) the car isn't even making 30 kg of downforce. Basically negligible.

A real GT3 car makes about 1000 kg of downforce at 200 kph, for comparison.

That's the problem though, some road super/hypers have too much downforce in the game, but only at the rear which causes serious understeer at high speeds.

The GT3 RS has 100 rear DF in the game. We don't know what unit it is, or at what speed is this achieved. It's lower than the 350 kg you quoted (which I assume is total front + rear DF), but higher than the 30 kg "usable" DF at 80 km/h. As a result this car just plows at high speeds because there's nothing on the front to balance it.

The Group 3 cars has something like 300 F/700 R in the game, which total gives 1000 kg possibly being accurate according to your numbers.
 

ScottPye20

I want to be monkey
Premium
10,716
Australia
Melbourne
ScottPye20
Yeah the aerodynamics are stuffed in GT Sport. I know this because I tested some cars in GT5 and found that their top speeds were actually closer to the real life speeds... I'll have to get the stats to confirm but I think the F40 did 325KM/h, the Veyron did 402KM/h and the Aventador did 347KM/h. The cars in GT5 are either 5KM/h too fast or 5KM/h too slow, which seems a bit more plausible than 20KM/h too fast or 20KM/h too slow. A complete overhaul of the aerodynamics is needed for GT7.
 
2,014
United States
Azle, Texas, USA
GTP_KinLM
KinLM
PD aero values has been shown to be messed up for a lot of cars.
- Road going hypercars often lack front downforce leading to severe understeer balance at high speeds.
This, in my experience, is more of a rear toe/suspension alignment issue in GTSport. Generally these cars will be set up to understeer with aero at speed, as Lewis Hamilton isn’t driving them and it’s much less.. lethal, that way.”

- Track cars like Vulcan are classified incorrectly and given too little downforce (it should have comparable amount to the P1 GTR and Zonda R for example).
Possibly. I’m not sure what the real life figures for each respective car is, but I don’t doubt it.


- The McLaren F1 has too much downforce for such an old car with simple aero, which results in it not being able to reach its real life top speed.
False, the McLaren F1 actually uses fans to help increase downforce (yes, it’s a fan car) and I believe that is what PD is trying to simulate here.
Keep in mind that the top speed of a “normal” F1 is not the same 240mph as the XP5 record setter.


On the other hand, the LaFerrari has too little downforce & drag, which results in ridiculous 400+ km/h top speeds.
False- This is actually a separate (and more serious) issue:

The Ferrari LaFerrari has an incorrect power figure.

All other hybrid cars in the game (such as LMP1, for example) have quoted HP figures for the combustion engine alone. LMP1H cars are quoted around 500HP but make close to 1000 with the added EV power.

This would mean that the LaFerrari should have close to 800HP listed, but instead it has the combined Engine+EV power of 960 quoted, meaning its making 960+160=1120HP.

Set the power to 800HP and suddenly the car achieves speeds far more accurate to real life.

This is actually something else I’ve really wanted to make a thread on but have lacked the time to.


Everything else I mostly agree with, or at least I’m not bothered enough by it to refute it.
 
LaFerrari as well. Zero front downforce in GT.

Meanwhile:

"The front wing was designed specifically to increase downforce by eliminating the negative effects of pitch sensitivity caused by the pronounced splitters. A broad central air vent on the front bonnet channels hot air away from the radiator. The front spoiler directs the external flow to the front of the outlet to improve its efficiency, thus creating compression on the front section of the bonnet which generates downforce,"

http://egarage.com/current-interests/laferrari/
 
624
United States
United States
"The F50 is one of the very few road cars that produces significant levels of downforce, to the tune of about 440kg.. What’s more, that downforce is distributed as it should be: 40/60 per cent front/rear,"

GT Sport: Zero front downforce :boggled:

http://www.audiosignal.co.uk/FerrariF50.html
I'm not saying Ferrari are lying, but in the 90s Ferrari had a terrible reputation for giving cheater cars to the press. And again we have the oft-used trick of quoting downforce at absurd speeds, a 200 mph downforce figure is almost impossible to independently verify.
 
2,014
United States
Azle, Texas, USA
GTP_KinLM
KinLM
Ford GT as well.


Reality: "Movable front flaps open and close depending on the angle of the rear wing, ensuring front and rear downforce is always perfectly balanced and you stay stuck to the road."

GT Sport: Zero front downforce :dunce:


https://www.topgear.com/car-news/supercars/heres-how-ford-gts-aero-works#6
Im not sure if you’ve bothered to read any of the rest of this thread, but it has already been explained/debunked. The amount of downforce produced by the heavy road-going Ford GT’s front end and some stupid flaps is not going to do next to anything, especially when compared to a much lighter GT equivalent with a large diffuser, flat floors, large splitter with venturis/expansion that actually leads to somewhere and creates a serious low pressure zone underneath the front end without incurring issues of flow separation.

Super cars are marketed to have downforce. Key word is marketed. In reality they weigh too much for the simple aerodynamic features to do much of anything.

Even the Dodge Viper ACR only generates roughly 1/2 the downforce of a proper racecar, while also weighing much more and thus reducing the effectiveness of the aero.

And, for the 3rd time, I would strongly guess that there are more underlying “aero”/grip figures for each car than the simple two numbers we see in the tuning menu, as I believe this was the case in past GT games.
 
725
Singapore
Singapore
XSquareStickIt
Ford GT as well.


Reality: "Movable front flaps open and close depending on the angle of the rear wing, ensuring front and rear downforce is always perfectly balanced and you stay stuck to the road."

GT Sport: Zero front downforce :dunce:


https://www.topgear.com/car-news/supercars/heres-how-ford-gts-aero-works#6

Actually, the Ford GT's case is somewhat understandable. In this game, the thing is stuck in Sport mode. In this mode, shutters in the front open to allow air to bypass the downforce generating tunnels in the car, to ensure "balance" of downforce when the rear wing is down. It's only when in Track mode, when the wing is permanently up, do the tunnels open up and give max downforce.

https://www.caranddriver.com/news/a15344043/explained-the-2017-ford-gt-supercars-five-drive-modes/

There are three things that point to the GT being stuck in Sport mode in this game: the knob on the steering wheel, its ride height, and of course, its rear wing. You can see the knob and digital dash display "S", with a "N" above and "T" below. In the same article linked above, it's explained that the normal ride height is around 4 inches (article claims 4.7), then dropped 2 inches when engaging Track mode. Ride height in this game for the GT is 4.13 in.


Granted, this game doesn't even seem to simulate that right, because it ALWAYS feels like zero downforce regardless of wing position.

This is another topic I've really wanted to bring up in hopes that GT7 will rectify: cars stuck in useless modes. I suspect the Ford GT is far from the only victim.

I didn't know the aerodynamics of GT Sport were so... effed up. It really goes a LONG way to explain why most road cars feel like utter crap to drive in this game. It was a really interesting and informative read, kudos all 👍
 
Actually, the Ford GT's case is somewhat understandable. In this game, the thing is stuck in Sport mode. In this mode, shutters in the front open to allow air to bypass the downforce generating tunnels in the car, to ensure "balance" of downforce when the rear wing is down. It's only when in Track mode, when the wing is permanently up, do the tunnels open up and give max downforce.

https://www.caranddriver.com/news/a15344043/explained-the-2017-ford-gt-supercars-five-drive-modes/

There are three things that point to the GT being stuck in Sport mode in this game: the knob on the steering wheel, its ride height, and of course, its rear wing. You can see the knob and digital dash display "S", with a "N" above and "T" below. In the same article linked above, it's explained that the normal ride height is around 4 inches (article claims 4.7), then dropped 2 inches when engaging Track mode. Ride height in this game for the GT is 4.13 in.


Granted, this game doesn't even seem to simulate that right, because it ALWAYS feels like zero downforce regardless of wing position.

This is another topic I've really wanted to bring up in hopes that GT7 will rectify: cars stuck in useless modes. I suspect the Ford GT is far from the only victim.

I didn't know the aerodynamics of GT Sport were so... effed up. It really goes a LONG way to explain why most road cars feel like utter crap to drive in this game. It was a really interesting and informative read, kudos all 👍
Yup, track mode gives maximum downforce, which implies the other modes will feature some amount of downforce.
 

LeGeNd-1

Premium
6,813
Australia
Australia
GTP_LeGeNd-1
@KinLM

1. Yes the extreme rear toe in doesn't help, but at high speeds the predominant force is aerodynamic. Yes I know road cars are set with understeer bias because it's safer too. But the high end super/hypers in GT still understeers too much. If you have Assetto Corsa, just compare the 911 GT3 and the LaF to the ones in GT. Granted I've never driven these cars IRL, but from all the reviews and videos of people much more qualified than me, these cars just suck to drive in GT.

2. Vulcan 324 kg @ 100 mph, 1362 kg @ Vmax https://www2.astonmartin.com/vulcan/discover
P1 GTR 660 kg @ 150 mph https://www.topgear.com/car-news/speed-week-2015/speed-week-986bhp-mclaren-p1-gtr-thrashed-track
Zonda R 2000 kg @ 186 mph https://www.autocar.co.uk/car-news/new-cars/pagani-zonda-r-revealed
So the Vulcan should have somewhere between the P1 GTR and Zonda R, but in the game IIRC it has the same as most road going hypers (probably 0/100 or 0/200).

3. Yes I'm aware of the F1's two fans. It was small though, and it only serves to maintain boundary layer attachment to the rear diffuser to provide a small increase in downforce. Not a full on sucker "fan car" like the Chaparral 2J/Brabham BT46/Red Bull X1. The rest of the McLaren F1 body is devoid of any aerodynamic features (apart from a small rear popup spoiler), and Gordon himself said many times it's made more as a hyper GT than a cornering machine (i.e. reasonable ride height, soft suspension -> so underbody downforce is minimal as well). But in the game IIRC it has 200/300 downforce which is a lot more than modern hypercars (which I agree doesn't have as much DF as race cars, but still more than portrayed in the game).

From 14:30 he discussed it and compared it to the new T50's fan.

4. Interesting on the LaFerrari issue. I'm aware of the power figure not including hybrid power in the LMPs, but never thought of this problem afflicting road cars as well. It makes sense in this case 👍 I still say it needs more DF (esp front) in game though.

In conclusion, I agree with you that most people overrate the downforce values of road going supercars, especially in comparison to full blown race cars. BUT, the road going supercars in GTS are still lacking - especially the front:rear balance is messed up. The Vulcan is just in the wrong class completely. It's just galling when the S-FR Concept Car, with such a tiny frontal area and probably zero wind tunnel testing, produces more downforce than a lot of the supercars.

Disregarding the numbers in the settings screen (I agree there is more numbers "under the hood" that we aren't privy to - the Chaparral 2J in previous games are listed as 0/0 despite it obviously having tons of grip), my most important factor is always how the car feels to drive. And it's really, really obvious comparing the various high end cars* in AC vs GT that something is not quite right in GT, even with only "second hand" reviews and impressions to compare to. I guess we'll never know for sure until we get every single of these cars in a wind tunnel and measure the vertical load, but for now, with the information available, my humble opinion is that GT have a lot of work to do in the aero department (along with tyres, suspension, weight transfer, FFB and track surface modelling).

I mean will GTS be a better game with everything modelled correctly? Probably not. I'd even say fixes for the penalty system, more cars/tracks, better career mode etc are what the mass players will notice first. But it doesn't hurt to make the cars better to drive. As I always say, realistic =/= difficult. Realistic = intuitive ;)

*If you have AC, I recommend testing the LaFerrari, 911 GT3, 458 Italia, Aventador SV, MP4-12C to know what I mean. Both games have all of those cars and all are vanilla cars (no mods) so you can compare like for like.
 
Last edited:
811
United Kingdom
United Kingdom
I've been in the Vulcan a couple times. Trust me it has massive downforce. Easy 1.8g braking. PD got it completely wrong.

Why it's classified as an N-car when it's not road legal is just bizarre.
I mean PD stick loads of cars into group-X. Why not this one and the ferrari so they could at least perform a bit more realistically.