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Advanced car setup guide

Discussion in 'Chit Chat Room' started by Andrew_WOT, Jan 7, 2016.

  1. Andrew_WOT

    Andrew_WOT Alien


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  3. kikie

    kikie Simracer

  4. Nao

    Nao Alien

    Pretty good read. Thanks for sharing it here!.
    Judging from some of the explanations of car behavior, the filler info (not specific to rF2 details on setups) looks kind of dated... For example, dampers, toe, diffs and weight balance sections have some old looking quirks that either can make the feature behave differently than stated in modern sims or it works properly but for different reasons. Fortunately the nice race/setup strategy guide more than balances that out :).

    Off to the top of chit chat it goes :p
     
  5. iVG

    iVG Alien

    @Nao , what do you mean by old quirks and what works differently in modern sims regarding dampers, toe, diffs and balance?
     
  6. Nao

    Nao Alien

    Toe - the idea that more toe-in on fronts helps with turn is only true in specific cases. Weather toe-in or -out helps turn-in depends on car and how exactly driver is executing the transition for given corner. More front toe-out helps in early turn-in (by destabilizing the car over road irregularities, where when tyre encounters a bump it is pulled into higher negative angles), while toe-in helps getting to optimal slip faster and decreases tyre flex time, helping more in mid to late parts of the transition.
    Also for me the "wear" and "decreased top speed" is getting old... Yeah excessive toe angles give noticeable effects on straight, but the odd degree (or less) of toe, that we use, barely gives any increase in rolling resistances and definitely is very far from adding any friction which the guide mentions (between tyre and road). Imho it just scares people off toe tweaking which can be quite helpful.


    Diffs - it has been discussed on the linked isiforums too... in general more power diff does not really increase understeer (and thus decrease front wear). Mainly because more diff lock on powered wheels transfers more torque to the outside wheel and the resulting unbalance of forces between left and right wheel, turns the car into the corner more (nullifying the normal understeery effect of diff lock in "free rolling"). And if we take a case where there is more power than grip** there is one most "understeery" setting per situation (usually 10-30%) and any increase of diff lock will have grip drop effect which increases overtseer.
    ** - it's really all about rear inside having not enough grip to stop significant slip (both for too low and too high diff lock settings)


    Balance - Getting more oversteer when shifting weight to front has nothing to do with aerodynamics (rather the downforce actually makes the effect smaller). It's effects come from 1) shift in relative ARB stiffness - more load = less stiff ARB. And 2) which has been vaguely noted is that weight shift influences brake balance and power balance.

    Some of the damper stuff - it feels based on some introductory information like simple "road" transitions that make sense in a vacuum but rarely happen while racing. For example the statement that "less front slow bump = more turn-in" is wrongly attributed to weight shift while it's grip related thing. I think the idea behind the statement in the guide, would be that when truing-in we shift weight from middle to outside, loading front outside tyre (bump motion), but during race we already are on the maximum load there from braking, and for the turn-in the only weight transfer happens on front inside (reboud motion) to rear outside (bump motion). There is no front bump movement at all so there is no way it would influence turn in any other way than just increasing overall grip over bumps.

    Anyways thats my take on it, some ideas might be wrong, others i saw in books... which also can be wrong :p ~ cheers
     
    Last edited: Jan 10, 2016
  7. iVG

    iVG Alien

    Completely agree, @Nao. Recently seen some pCARS setup tutorials (this is not a rant-starter towards pCARS) of a pretty knowledgeable guy, he talked about differentials and, as usual, he stated that higher power lock gives more oversteer, less gives understeer. Well, there's the perfect example of how most people approach setups with black and white thinking. 'This gives you understeer , that gives you oversteer' , which is not the case both in real life and in AC.
     
  8. Spinelli

    Spinelli Simracer

    Nao, I'm particularly interested in what you said about front toe...

    In past sims (especially ISI engine based) I always liked less negative toe than, it seemed, a lot of people. I didn't need, or liked, the ultra responsive front-end on initial turn-in and could do top 5 and 10 GTL and RF1 rank laptimes with almost any car i tried so it defenitely didn't slow me down. However, in specifically RF2, I notice that as I lower negative toe (like I always do in most sims/cars), I actually loose mid-corner grip as-well. My fronts will start understeering sooner all throughout the corner, including the middle of the corner as i'm applying more steering lock, rather just dictating initial turn-in behaviour. Therefore, in RF2, I seem to have to run more negative toe than usual or else I loose-out on sheer corner grip compared to others. So my question is, is toe supposed to have such a dramatic effect on sheer front grip throughout the corner (particularly mid-corner) as I seem to be experiencing in RF2?
     
  9. Nao

    Nao Alien

    @Spinelli The first thing to clear: what is the range of toe change we are talking about? Something like 0.2°-0.3° or something big like above 1.0°+ ?

    In general i don't think that until ~1.0° toe (from optimal so something above +0.6° toe-in) we should be able to feel grip difference mid corner (unless it's like alien level setup). Due to various factors some negative toe should help saturate grip on both front tyres at the same time producing most optimal grip, but the exact amount depends on factors like: tyre flex sensitivity due to load, ackerman geometry, corner radii, overall grip balance as well as momentary weight (load) balance. (edit: heck race series too, NASCAR is much more sensitive to toe than let's say F1)

    Racecars are made so that the optimum toe for cornering should end up close to zero on straights. But i guess thats not always given... so how exactly toe would affect entry and cornering can be car/track dependent. And with that, can you give me an example car to pick and mess around with... (preferably something vanilla, i've not touched rF2 for quite some time now... could be fun messing around again.)?.
     
    Last edited: Jan 11, 2016
  10. iVG

    iVG Alien

    Yeah I can test too if you give us a car.
    I have found that the Toyota GT86 is very sensitive to toe and different can be felt almost instantly. Also there isn't much else to change there apart from camber, toe and pressures so it's a good test car. It really come alive if you open up the wheels a little bit (give it a bit toe out), the rear gets really happy and manages to follow the front even on semislicks. If you manage to 'learn' how to adjust the car behaviour with toe and pressures, you should be able to translate this to different cars. Obviously, with some adjustments depending on geometry but there's the general idea.
     
  11. Spinelli

    Spinelli Simracer

    Well i'm not talking about unrealistic values, I'm talking about something like between -0.05 degrees to -0.40 degrees. I usually like less toe-out so I would lower the toe to something like -0.05 to -0.15 degrees but in RF2 I can notice quite a bit of mid-corner grip loss relative to a setup with higher amounts of toe-out (eg. -0.20 to -0.40 degrees). The front tyres seem to give up at less and less amounts of mid-corner steering lock as toe-out is reduced more and more (eg. going from -0.40 to -0.30 to -0.15 degrees).
     
  12. Nao

    Nao Alien

    Edit2: (rewrite) I'm not sure actually. Grip limit steering angle change with toe changes is given just by geometry. What would be important is how much laptime are you loosing with different toe? It should not be big... unless it's some very peculiar car.
     
    Last edited: Jan 11, 2016
  13. Spinelli

    Spinelli Simracer

    Well I can't turn the steering wheel - the front tyres - as much as understeer will come about sooner. I can't ask as much out of th front tyres, they give up, gripe-wise, sooner and therefore I can definitely gain laptime from the higher mid-corner speed my front tyres can handle as I make my tyres toe outwards (more and more negative) more and more. It doesn't seem to be a particular vehicle thing but more of a general core physics engine thing. I guess it's something I should ask in the RF2 forum but I just would have liked to have your general thoughts about that in real-life and AC, so thanks for that.
     
  14. Nao

    Nao Alien

    @Spinelli In AC (especially in newer versions) there is a bit more leeway around grip limit so it's more difficult to spot toe influence mid corner (grip does not change by much).
    Considering that with stiff ARB's cars like open seaters have outside front wheels with possibly more than 10x the load of inside ones, for whatever angle mismatch (due to toe or other factors) that happens on the inside tyre, the grip difference should be negligible. (Heck modern F1 sometimes lift inside front when cornering, completely negating the possible impact of toe).

    There are things like anti-ackerman geometry (for racecars) that add toe-in during cornering, while at the same time generous toe-out usage is often recommended, both kind of contradict each other, so i don't think there is any golden rules regarding toe... As Carrol Smith writes as a final word on toe "It is not very critical". Also Milliken mentions that suspension stiffness under race loads can produce higher wheel angle deviations than the toe or Ackermann settings which again hits at lower significance of toe for pure cornering grip. (There seems to be no firm stance on toe with regards to cornering grip in any publication i had.)

    Also I've tried driving formula renalut 3.5 in rF2 too and the difference between 0° front toe and -0.5° or even -1.0° was really small grip wise. Could compare it to something like -0.2° camber angle... so combining all of that, what you experience it's probably something quite specific, possibly car or even setup related, or maybe a quirk in rF2 physics model that would impact only a set of cars. Can't help you more with this ~
     
    Last edited: Jan 12, 2016
  15. Spinelli

    Spinelli Simracer

    Ya, I'm not sure, I've noticed it on GT3 mods, 60s open wheelers, modern day Clio Cup racer, modern day Nissan GTR racer, and quite a few others. It's quite evident to me once I've done enough laps with a car/car-setup/circuit combo. It does sound like an issue according to what you're saying and what you've quoted but that's for the RF2 forums I guess.
     
  16. nijeat

    nijeat Simracer

    The pdf link was dead. Do you anyone have a new link?
     
  17. Nao

    Nao Alien

    "The links to the guide have been deleted for commercial reasons. Thank you for those who have expressed their support and appreciation, David"

    Lol are they going to sell that? Or is it just a copyright shutdown by owners of pictures/parts of the text :p ?

    Either way i'm not going to post any links here but @nijeat if you want to demo the content of that pdf send me a PM
     
    nijeat likes this.

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