Mechanical setup discussion

Discussion in 'General Discussion' started by Slip_Angel, Oct 28, 2020.

  1. Slip_Angel

    Slip_Angel Registered

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    In this thread i want to discuss about mechanical setup.I will post what i know, i'm probably correct about some stuff and wrong about others.

    Spring rate->>
    There are some main conditions i look before choosing springs rate
    •Surface type
    •Speed of corner
    •At what speed i have to brake
    Etc there are other factors as well.
    One thing i'm slightly confused about is how spring rate affects the camber gain and overall suspension geometry.
    For example i believe that having stiffer springs rate means less body movement hence less camber,toe variation in pitch,squat,roll etc.
    What this means i can run with lower static camber and toe values hence i don't sacrifice my braking and acceleration grip.Is this correct ?

    Next thing is spring rate split front to rear (how far apart are spring rates on both axel)
    I tested this and came to conclusion that having too much difference between front to rear spring rate is bad.So i generally don't go over 2 clicks of difference.

    Anti roll bar->>

    I learned that having too stiff anti roll bar will put too much load on outside wheel so in this sense i think it is better to keep it as low as possible.
    But sometimes you have to choose softer springs for bumpy tracks so here IMO choosing stiffer anti roll bar would gain back some of the roll stiffness that you lost with soft springs rates.
    BUT again if there are heavy kerb usage then i would try to stiffen springs again with lower anti roll bar,this way wheels are
    more independent of each other.

    I also think that increasing the springs rate provides better rolling stiffness than anti roll bar i.e more resistance to rolling motion of car is better achieved by stiffer springs than anti roll bar , i might be wrong so please do let me know.

    Same thing with anti roll bar which i think is true is that stiffer anti roll bar
    allows less body roll hence less camber variation in corners hence
    less static camber.

    Feel free to add more on anti roll bar and springs rate below. These are the things i can think of right now.
    I'm definitely missing good bit of details and probably wrong about some things i posted above.

    Dampers->>

    I will not go into fast damping but just add my understanding of slow damping.

    What i know is that springs changes its character with its stiffness
    ex-> a stiffer springs will compress less compared to softer springs for same amount of force
    This gives me crucial hint on how to tune dampers when i change springs.
    Generally stiffer springs rate can allow softer slow bump settings.
    This way i can gain back some grip back with stiffer springs rates

    Rebound is different story, stiffer springs rebound harder and faster so with this i know that rebound damping needs to be stiffer than bump. The stiffer the springs the more slow rebound damping i add BUT as i mentioned that with stiffer springs i generally lower the slow bump damping.
    This creates a problem, what would happen if i have to run much higher slow rebound value than slow bump value?
    example-> if there are 20 clicks on dampers then what if i kept the slow bump at 5 and rebound at 18 ? will this work?

    I also believe that slow rebound acts similar to anti roll bar in roll motion of the car.
    A good value on slow rebound will keep the given wheel(and body) low while entering the corner
    for example take a left turn here the inside wheel will go into extention so with stiffer rebound i can slow down this extension and gain some entry bite on front.
    BUT if i go way to stiff in rebound then it will cause more loss of grip.
    This is why rebound value is IMO heavily dependent on springs rate.
    A softer springs will extend slow but further so here you need just enough rebound to not overextended the inside wheel coming into corners.

    On aero cars having stiffer rebound on front may increase exit front end grip as it keeps the splitter low to the ground, on other hand if rebound value is stiffer on front on slow speed corner exit then it will mostly cause understeer.

    on rear, stiffer rear rebound generally helps in faster corner entry as it keeps rear low but IMO having too stiff rear rebound will cause oversteer on slow corner entry.

    There is definitely more info so please if you have any add in comments also if i'm wrong do point it out.
     
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  2. Comante

    Comante Registered

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    Without considering the specific vehicle to which a setup is destinated, make this deceiving. Some general concept are... general, but those are info that are already covered from most setup guide of any game avaiable.
     
  3. mantasisg

    mantasisg Registered

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    I am also regularly thinking about many of those things. Interesting to read how you interpret how these components work. I think about some of them the same way, some different way. Also just trying to figure out stuff, and improve stuff that I suppose that I probably got figured out...maybe...

    Many stuff to talk... but I just wanted to say for now. It is particularly interesting about how you figure how stiffness of springs should relate with dampers settings, I think you make good sense there. It is very simple, I mostly look for simple ways to explain stuff, if you can explain something simply and it makes sense then it is awesome.

    I also tend to think that as easy as possible anti-roll bars are best. But it might not be entirely true in most cases. For a good reason they are also often called "stabilizers". Much too low rolling stiffness might make car difficult to keep steady, unexperienced drivers even might induce instability themselves if very low rolling stiffness will allow large amplitude oscillations. I think that perhaps high grip of tires has great influence on stiffer rolling resistance, that is so because if tire slips a little bit (small slips) it is also some kind of damping, but if tire snaps in with great grip very quickly, the moments might be translated into chassis too soon making the car unstable and leading into resonating oscillations such as - tankslappers. Higher rolling stiffness frequency might be just simply required when very high grip is being generated.

    The amount of wheel travel allowed definitely depends on geometry. Obviously some cars may have too much bump-steer or bad camber changes at particular amount of travel. Besides that particular amount of stiffness comes from chassis itself: the actual stiffness of chassis, rollcenters height vs CoG, antidive percentage of geometry, antisquat percentage of geometry, motion ratios of the springs, I think the suspension links orientation as well... plenty of stuff...

    Speaking of clicks in the setups... I'd avoid that when talking about stuff in general. Clicks makes sense for particular components of certain make and model, when it is know what is the unit of one click. Who knows what one click for what means... often that can end up as placebo, if one car "a click" is equal to ten clicks of other car.
     
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  4. Slip_Angel

    Slip_Angel Registered

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    Good points mate, thanks for that.
     
  5. benborp

    benborp Registered

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    Could I suggest you look into suspension frequencies?

    That will tie many of the mechanical elements together and also illuminate areas in which you are lacking the data to make rough rules of thumb without doing any testing.

    Once you know which data is missing you can formulate a programme of testing to fill in the blanks.

    Edit: Oh, and edit your json to enable scientific units in car set-up options. That will remove a ton of guesswork and supposition.
     
  6. Slip_Angel

    Slip_Angel Registered

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    Thanks for the tip i will look for json file.
    Regarding suspension frequency and other stuff you mention how do i get such data in RF2 ?
     
  7. Slip_Angel

    Slip_Angel Registered

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    Could you please tell me where is this json file ?
     
  8. Lazza

    Lazza Registered

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    rFactor 2 folder, Userdata\player\player.JSON. Open it in notepad++ or similar (notepad can work, but I think occasionally can mess up the file format).

    I believe what's being referred to is in the Game Options section:
    "Damper Units":false,
    "Damper Units#":"Display dampers (shocks) in garage as: 0 = setting (e.g. 1-20), 1 = rate (e.g. 1000-9000 N\/m\/s)",

    changing 'false' to 'true' should enable the actual rates. Bear in mind if a car has overridden the default display that setting won't do anything.
     
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  9. Slip_Angel

    Slip_Angel Registered

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    Nice, i will look into it. Thanks mate
     
  10. John R Denman

    John R Denman Registered

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    Suspension tuning is a balance of science and art in the intuitive manner; can be a bit overwhelming when learned piecemeal.

    Armed with a basic understanding of the expected physics of maybe a dozen settings, is the science; making that connection to what's needed is the art.

    Its the tires we're trying to manage. Keeping enough force on the ground to the correct tire with oscillations dampened just enough to not bottom out. Keeping the contact patch in the optimal point as the tire carcass flexes.

    Watch replays of critical regions (usually where one keeps crashing...) and think of what the driver is doing; throttle, brake, shifting, steering....What are the tire temps telling you? What elements are unloading the wrong tires? Pick one and only one. Make changes and feel the responses, take a few laps. Keep doing that until you've got the feel. Than move on to the next tuning parameter. Spend 40-80 hours cycling through them. If you make that connection while practicing you'll master tuning pretty quickly.
     
  11. Slip_Angel

    Slip_Angel Registered

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    Yep setup is really artistic. I'm currently setting up the cars just as you said, by feeling what car is doing while driving. I keep mental notes on how car is behaving on slow,med and high speed corner.
     
  12. Slip_Angel

    Slip_Angel Registered

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    Hey thanks for letting me know about scientific units, i enabled it but sadly only radical has shown me actual values (N/m/s).
    Is there other way to enable this with other cars; i currently only drive M2, Porsche Cup, RSR and 488 GTE.

    Also how do i use this "new" data to tune my dampers ?
    Can anyone please point me to good resource to read about it ?
     
  13. Slip_Angel

    Slip_Angel Registered

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    Okay so i'm not so sure about this theory of mine so i will post it here, maybe more knowledgeable people here could confirm or deny it.

    Lets take example of load transfer( NOT WEIGHT transfer)

    ** Note the numbers i will be using are totally made,just for example purpose **

    For example ->>
    Lets say car has a longitudinal load transfer under power of 500kg in straight line to rear axel.
    Now i want to know how changing springs rates ONLY affects the distribution of this ( remember key word is distribution, i know suspension and other components do NOT changes amount of load transfer but they only affect how that load is shared and transmitted )

    So lets take 2 spring rates
    A) 100 N/mm
    B) 200 N/mm

    So here is my theory->>
    if i put 100 N/mm springs then this will mean IN MY THEORY that the given load transfer (500 kg as told above) is relatively more "absorbed" by suspension and car's body hence you get more suspension travel and car squats more in softer springs.
    This means the total load is slightly more absorbed by chassis,suspension hence now tyre has slightly less load on it.
    For example lets say the suspension absorbed 100kg out of 500kg now only 400kg of load is on tyre.

    Now if i pick second spring rate ( 200 N/mm one) this will mean the total load transfer is more "directly" transmitted to tyres and less suspension absorption hence less suspension travel.
    In numbers lets say that by picking 200 N/mm spring only 50 Kg of load is absorbed by chassis and rest is on tyre i.e 450 Kg

    Yes in this theory more load is on tyre by choosing stiffer springs BUT IMO due to tyre load sensitivity more load does not mean more grip.

    This is another reason why IMO softer springs provides more grip apart from softer springs allows tyres to "deform" with surface.

    Remember this is about load transfer NOT weight transfers.
     
  14. Comante

    Comante Registered

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    It doesn't work like that. What changes is TIME that load takes to transfer. Softer springs mean longer times. Yes softer spring yeld more grip, because TIRES will conform to road surface better. But in racing you want shorter reaction times, so you stiffen the springs, so load transfer are faster, yes, you lose mechanical grip in doing that, but you get the possibility to make the car more agile and nimble.
    You have to imagine a vertical pole with a weight on top, at the base, 4 tiny springs : the softer the springs are, the slower the weight move around and larger the movement is. Stiffening the springs the weight will move faster and inside a smaller circle.
    But the total weight on the 4 springs is always the same.
     
  15. Lazza

    Lazza Registered

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    @Slip_Angel can you explain what you refer to as load transfer, vs weight transfer? If language gets in the way it's hard to talk about these things.

    2 things I would say off the top:
    • Load sensitivity means grip isn't proportional to load. A tyre with 5000N load will provide more grip than one with 4000N, but not 25% more (5000/4000) (ignoring extreme load effects)
    • Any spring with a load x on top of it will transfer that entire load x to whatever the spring is sitting on, a stiffer spring will just be less compressed.
    You might be aware of those, but again language can confuse things. I see Comante has addressed the spring movement as I type..
     
  16. Slip_Angel

    Slip_Angel Registered

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    I was in doubt about my theory anyways, Thanks for clearing that up guys. Really appreciate.

    @Lazza If i understood correctly load transfer is basically the forces while driving. The amount of Gs a car does while acceleration (lateral and/or longitudinal) is load.
    On other hand weight transfer is actually weight of vehicle moving around i.e body movement.
    I also learnt that weight transfer is very small on modern race cars as actual body movement is very minimal.
    hope i'm correct
     
  17. Lazza

    Lazza Registered

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    Ok, yep. I think you can ignore the effect of moving centre of mass as it's very small. The confusion is which to call it, as many in racing refer to load transfer as weight transfer, so it's good to be sure which you mean. Safe to say hardly anyone is actually talking about weight transfer :D
     
  18. Comante

    Comante Registered

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    Modern racecar can be very stiff, but this doesn't prevent load to shift, otherwise you won't have oversteer or understeer. What probably help more modern vehicles is that stiffer suspensions mean lower ride height and lower COG . It's all related. If you see the car from the side and draw the various vectors that act on the system (like gravity on the cog and drag on the contact patch while braking ) you will be able to visualise what happens even with just a scholastic knowledge of vector physics. In short braking (and acceleration) induce a torque moment in the body , thus front or rear axle share a different proportion of the car weight , geometry of the system influence how much and how fast those transitions happen.
     
  19. Lazza

    Lazza Registered

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    @Comante this is confusion of terms. Everything you're describing comes under load transfer, weight transfer is something else we don't really think about and is of much less significance anyway.
     
  20. Slip_Angel

    Slip_Angel Registered

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    No worries mate, confusion will not help in such conversations.
    I agree that weight transfer is very low especially in these modern race cars.
     

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