GT3 Challengers Pack - Audi R8 rear tyres problem

Discussion in 'General Discussion' started by #SM12, Mar 1, 2019.

  1. #SM12

    #SM12 Registered

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    Hi guys, I wanted to know if anyone has found problems with the rear tires in the new mod gt3.
    I encountered a very acute problem at the rear tyres, with the Audi: after about 5 laps in any circuit, the rear tires lose grip, despite the consumption being normal and the temperatures relatively low. I thought it was a matter of set-up but after comparing myself with other people and making a huge amount of changes to the set-up, the result does not change.
    I tried with the various compounds available but the problem reoccurs the same after the same number of laps.
    It almost seems to drive in the wet at the rear, while the front continues to have a remarkable grip. I tried to do the same tests with the other cars of the package but I did not find any anomaly.

    At this point I wonder if it is actually a problem of the mod and the car, or is caused by the frame of the Audi, as very rigid.

    Does anyone know anything about it?
     
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  2. gluon

    gluon Registered

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    The Audi R8 LMS is one of my favourite cars on that pack and I've been driving it around a lot without feeling any abnormal loss of grip at all. Surely the default setup is too oversteery for me and even after tweaking it to become more neutral, the rear still likes to step out a bit, so I try to be very gentle with the throttle at some faster corners. That said, even when I was driving aggressively and using soft tyres I never felt what you described.

    What exactly do you mean by losing rear grip as if it was wet? Is it undriveable even if you're more careful? Like I said, the Audi has this natural tendency to slide and requires some taming of the right foot.

    Have you tried to stiffen the front anti-roll bar and/or soften the rear anti-roll bar?

    Have you tried to stiffen the front suspension and/or soften the rear suspension?

    Also, on what tracks have you been driving?
     
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  3. tosh

    tosh Registered

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    Hi everyone, I am facing the same problem. I get through the first laps quite comfort but then the grip on the rear outer tyre drops and temps are getting high. At this time with no setup tuning etc. and a traction control in game of 0 and car on 3 or 4.
     
  4. John R Denman

    John R Denman Registered

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    I've noticed a few changes over the last year to the tire thermodynamic physics but only one time was anything mentioned in the monthly newsletter. Trouble is the current thermodynamics model totally undermines the other exceptional qualities. I get the chance to run some sessions on rFactor Pro and it's quite a different and better behaving package regarding thermodynamics. Trouble is after doing an rF Pro session and coming home to my rF2 package its like the difference between eating Grade A Filet Mignon or a cold hot dog in a soggy bun.
     
  5. tosh

    tosh Registered

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    With the C7 I don't have that much trouble, really annoying :) That car produce consist laptimes over and over.
     
  6. John R Denman

    John R Denman Registered

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    GT3 P2, and MAK mods don't seem to suffer too badly from the erratic heating characteristics, mostly open wheel cars. Its especially notable when comparing MoTec files before and after some of the rF2 exec file updates. One track I use for calibrating is a simple flat round skidpad track running at the same constant speed. Some exec changes produced over 80° swings in tire temps, and the next update tends to have some correction. Most of the time I use rF2 as a simulator to play with suspension tuning not so much to do any racing online or offline. My racing days were over about 20 years ago....
     
  7. Stefan_L_01

    Stefan_L_01 Registered

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    Hi
    Where can I find a skidpad track for rf2?
    Thx
    Stefan

     
  8. TJones

    TJones Registered

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    I can't agree/disagree here, i didn't check it myself. But i just hope you're right and they still try to improve the tyremodel or physics in general.
     
  9. TJones

    TJones Registered

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  10. Paul McC

    Paul McC Registered

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    I wondered why this was for a while so i did some tweaking. In short, Its cause it runs a ridiculously open pre load on the diff with default setups, on 15! Knock that up to 25 or above, should sort you right out!
     
  11. davehenrie

    davehenrie Registered

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    Paul, let me thankyou for something. Instead of just saying the diff was open, you gave numbers to correct the problem. There are A-LOT of casual racers/drivers that may never know what an open diff is. At least with your post, you presented the solution in a simple clear answer.
    thanks again.
    dh
     
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  12. Paul McC

    Paul McC Registered

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    Hey man thankyou very much! Im so glad its helped, a pleasure mate!

    I am refering to the official S397 Audi so I hope thats what everyone else is talking about (seemed to be but was'nt quite sure).

    Anyway as for the effect occuring after several laps I can only assume (from my limited knowledge) that maybe the diff gets slightly looser as things warm up (i say this because i was finding the problem was most apparent when lifting off the throttle).
    Now you can adjust the pre-load, but ive no idea what the power and coast ratios are set to as they are non adjustable and don't state what they are at (unlike say AMS2 where these values are shown, but also adjustable on the same car), but i assume it runs less lock under coast in the RF2 version.
    Also i wonder if there is any viscous locking in the Audi (IRL & in RF2) as i thought the loosening of the diff could be down to viscous fluid getting up to temp. These are all just guess'es really so please dont take my word on any of this (apart from locking up the diff more, that definately does work).
    I also had a thought that because the rears might be spinning a bit on the inside due to too much open diff that after a few laps the rear tires maybe get a bit too hot whilst the fronts remain at optimal temp so grip slightly better, as i thought i noticed that with he diff more locked up the rears teneded to keep a more consistent temp (if not overdriven of course), but that could just be me imagining things.
     
  13. Paul McC

    Paul McC Registered

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    Ok yup, turns out I was'nt dreaming. Just did some testing running about 6 or 7 laps with diff at default 15, then at a much higher lock of 50!

    Results, yes it is very much to do with both diff and tire temps! (and also how you have to adjust your driving style for each).

    With the diff open (and also taking into account that the more laps you do, the faster you go as you gradually push harder), it allows for the car to really rotate and lean on that back end hard, especially under lift off, after a while of this the rears get hot, and if you keep pushing harder they get too hot (went up to 100 after one corner) and the back end starts to hang out. Now even if you are under power coming out of a corner after getting them to hot you can have the back end come out aswell cause they've got too hot under lift off and hav'nt had time to cool before you power out.

    With the diff more locked up your rear tires stay much more within the optimum temps, back end is much more manageable, although you do loose some of that manoverability you've got with a more open diff, in fact in theis test i was actually getting better times with the open diff.

    Unless you try and power slide out of each corner with a more locked diff, its gunna keep the tires in better shape temp wise, although this is at 50 preload, so im sure if you go to the other extreme (as much lock as is possible on this car) that may also cause tires to overheat as you might be fighting the diff to break traction to get more turn.

    At the end of the day its all about happy mediums and driving style, or so it seems. Run with the open diff, don't lift off too much and remember not to over do it on corner entry speed, run with a more locked diff and its not so much of a concern, but car aint gunna change direction quite so nimbly!

    Then again, I could be wrong!

    I love this disscussion and all these little details you can change on a car in a sim, just love it! Cheers!
     
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  14. Paul McC

    Paul McC Registered

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    P.S. all my testing was done using no ABS or TC, sorry i forgot to mention that
     
  15. Lazza

    Lazza Registered

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    Pretty sure diff temp isn't a thing in rF2. But obviously tyre temp and condition will evolve over time.
     
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  16. Paul McC

    Paul McC Registered

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    Yeah I think you're right, it was the diff setting affecting the tire temps
     

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