Suspension and Aero

Hello,
I'm recently got back into RF2 after long time.My setup knowledge comes from ACC gt3 cars. So i was wondering if same principles apply here as well.I'm playing porsche RSR currently
So heres my current understanding->>

•To manage pitch sensitivity on initial braking or coasting can be controlled by stiffer front springs and slow compression damping and also with stiffer rear springs and rebound

•To manage squat stiffer rear springs ,slow compression dampening and using stiffer front suspension along with stiffer front rebound so that the front does not lift too much

•Body Roll cause loss of underbody aero which could cause understeer or oversteer, overall just loss of underbody downforce.
so run as stiff front and rear ARB as circuit allows.This will stop the inside body from raising hence generating overall more downforce.

•Some rake actually is better for proper underbody downforce, ACC has a front aero variation which is helpful unfortunately there nothing like this in RF2.
(If there is any info on how much rake some of these GTE,LMP cars run that would be very helpful)

I'm definitely missing somethings but anyways i just want to know how the suspension affects body characteristics and hence underbody aero in RF2.

 

Mostly thats correct. RF2 tends to behave very close to real car setup with some deviation on tire pressures and heat distribution, but its not far off there given the limits of CPU capabilities to process the complexities of this in real time. That is true when the car models are built accurately to the real cars anyway.

ARB's won't always need to be set full stiff, in fact rarely should they be. The stiffer it is, the more heating takes place on the outside tires adding to wear and loss of grip. Camber and Caster are better used to offset the roll to maintain grip and even tire heating; its a balancing act.

Dive & squat can be managed both by springs and bumpstops. You'll want some dive and squat as it gives the driver a little better reactance an feel to impending lockups.

Damper settings are vital. Dampers don't limit the motion, they affect the time it takes for motion to occur. Driving at the edge there is a fine line between traction loss which falls off quickly when the peak grip is exceeded. Allowing some suspension movement over a period of time say 50-100 milliseconds gives the driver more time to feel and modulate braking, turn-in, throttle lift etc. as the drop off from peak grip is extended through the suspension movement absorbing some of the energy.

Trailing throttle oversteer is a good example for damper tuning. If the rear tends to snap on throttle off, reduce the rear slow damper rebound rate (or fast if slow isn't offered). That slows the weight transfer to the front so the rear grip isn't lost so suddenly.

Many of the modern GT mods have built in driver assists in the tuning panel, I always turn them off. Once the car is tuned properly they just slow me down even with F1 cars. They may be helpful for extending tire life under endurance condition, I can't say for sure as I've never used them. Driver assists are most helpful for those who don't understanding tuning.

 

This sounds logical, but is there a way to know how am i managing the roll with camber and caster ?
Also how to know when is too much ARB ?
I too never go maximum stiffness on ARB i generally stay 1-2 clicks away from max possible value.

Yep i agree on this one. BTW what is bumpstop in RF2 ? perch distance?
I don't think i saw "bumpstop" written in setup screen on RSR.
Any info on how to setup perch would be greatly appreciated.

This is quite strange for me, i always thought that damper stiffness may affect the suspension travel.
I imagine compared to soft damper the stiff one will absorb the energy hence limiting the suspension travel/motion hence body motion as well.

 

So i did some testing specifically on rear springs on RSR at sliverstone
First i softened the rear springs all the way down 180N/mm and then turn the car on coasting around 216km/h, it understeered

Then i stiffen up the rear to 320N/mm and did the same thing at appox similar speed,steering angle etc. This time it oversteered

Seems obvious but hear my theory

I was under the impression that stiffer rear springs will resist the pitch of trailing throttle and it will stop the diffuser from rising too much hence maintaining downforce.

 

Aero doesn't attach the car to the ground. It puts more load on the tyres which gives somewhat more grip, and all acceleration (accelerating, braking, turning) is done using that grip.

So, you don't compromise spring balance massively to try and maintain perfect aero - the gain is offset by the loss in suspension efficiency. Some tuning will help, but not extreme.

Anti-dive and -squat are designed into the suspension geometry, moving some of the weight transfer away from the springs completely. You can't adjust that as a driver, but it should be a good compromise already. (between driver feel and a stable aero platform)

Optimum rake angle is largely constant in rF2 I think (bearing in mind very few corners are exactly alike, so your best rake will still vary - and the diffuser centre of downforce will usually move with rake changes as well), but it's still an optimum. If a car's base setup has rake somewhere near optimum, keeping the same setup ride heights with much stiffer springs at one end will move you away from optimum rake mid-corner, as well as upsetting the mechanical balance as above.

To clear up damper vs suspension travel: "stiffer" dampers don't limit suspension travel, but they do slow the spring compression with a given force. When driving over undulations this will lead to a reduction in travel simply because there isn't enough time to reach the same points.

Bump rubbers are adjusted with packers. You likely can't directly see when they're engaged, you may be able to work that out with telemetry analysis.

 

Yep, this is what i concluded as well i.e with these GT cars both in ACC and RF2 too much stiff suspension may keep underbody more flat but the loss of mechanical grip even at high speed is more important.
I wonder if this is due to
A. Not enough underbody downforce
OR
B.The cars are too heavy for downforce to be that effective,

As far as my understanding goes lighter cars like F1 will be way more affected with downforce than GT cars which are easily over 1300Kg.
I don't think these GT cars produce downforce that is higher than their weight maybe at very high speed (over 250km/h)

About Rake i agree with what you are saying, i knew that but what i wanted to know is how much rake will be best; Let me explain
If i go too much low at the rear it may seem like i gained some downforce BUT in reality the car is understeering because the splitter is moved upwards.
what i know that even if center of pressure is forward with some rake and this may seem bad balance but in reality diffuser is working optimally.
I'm currently using 0.6 cm or 6mm on RSR at sliverstone seems to be fine maybe.


About Damper
Thanks for clearing that up, logically it seems unrealistic but after seeing above replies it may be true.
So just to be perfectly clear lets take an example
Suppose on a flat surface you take a turn and suspension travel at peak load on outside tyre is say 15mm on Softest compression damper
Now if i take same turn with same speed etc but this time the compression damper is at maximum stiffness So does this mean suspension travel on same wheel will remain at 15mm at the same part of corner ?
Or will the car just go into rebound as the time it took to compression we were already exiting the corner ?

About packers
Does higher number mean more suspension travel before it hits bumpstop?
I don't think i saw any way to adjust stiffness of the bumpstop.

Again thanks for answering and sorry for another long post.
Car setup is becoming my favourite thing,i can go all day about this stuff lol.

 

Even if you have an un-encrypted mod and graph the diffuser response against front and rear ride heights and rake, you'd have to find a compromise because the ideal will change from corner to corner (braking intensity, speed, and any gradient changes). I think you'll make as much headway with some testing like you're doing, and find some good guidelines for yourself that way.

If you take a long enough corner, the sustained outside compression will be the same within a normal range of damper values. Stiffer 'slow' dampers will make it take longer, but the end result will be the same. That's assuming you have enough time to reach that compression. The compression will be determined by the springs, not the dampers.

Slow dampers tend to be used to control the rate of body roll, which will reach an end-point if the event (corner, braking, accelerating) lasts long enough. Quick chicanes and bursts of acceleration won't. Fast dampers deal with oscillations like track bumps and kerbs and will (very likely) never reach an end point, so the amplitude of those oscillations will be impacted by the damping rate.

Constant state - for long enough - leaves the dampers with nothing to do.

Higher numbers means more 'packing' behind the bumpstop, which moves it closer to the beginning of suspension travel. Therefore you hit it earlier. You can't adjust the bumpstop material, it could be done using vehicle upgrades but not with setup options. And you won't see it in any vehicle upgrades I'm aware of

 

Much appreciated info mate.
I will make setup with better knowledge now.

 

what are you referring to at the end of the paragraph? ride height? the difference between front and rear? Im not challenging, but questioning. I was following along til here.

 

Yes i was talking about rake, the difference between front and rear ride height. My bad i wasn't clear.
I'm currently at lowest front ride height 5.0cm and rear is at 5.7cm.
Hence my current rake is 7mm.

 

Thanks for educating me!

 

Hahaha this no big deal,Anyways glad this discussion helped others people as well including me.

 

It is helping, this thread is pure gold, sticky material.

 

Thanks to some knowledgeable people in this forum,some of misunderstandings has been cleared.

 

Just me being pedantic, but shouldn’t that be 70mm?

 

Not being pedantic, but you might want to check your maths

 

Well fark me.....you’re right again as usual.....was thinking metres instead of cm...carry on all, interesting discussion

 

Just to expand a little on rake, keep in mind it's dynamic. The setup ride heights and resultant rake are based on 0 fuel and sitting still.

As soon as you jump in the car and start actually doing stuff, the ride heights and rake will move all over the place.

And, because rF2 applies your setup every time (including ride height), you can have the seemingly illogical scenario of softening rear springs with the intention of reducing ride height with downforce, and end up with a higher mid-corner ride height than before - or vice-versa.

It's easy to look at setup ride heights and judge rake directly, but it's what happens when under load that matters.

One final note: the ride height figures are based on the mod's defined undertray points. This won't necessarily be right next to the wheels, or exactly on the vehicle undertray graphically. A mod will hopefully have sensible points though, and all the rake and other derived calculations (like diffuser downforce) are all on the same page.

@Goanna I'll go full-pendant for a second: you would have meant dm (decimetres) for that to be correct

 

no idea what one of them is .... certainly fubar'ed my maths though.