Very strong braking FFB (BMW M2 CS Racing)

Discussion in 'General Discussion' started by HomieFFM, Dec 6, 2019.

  1. avenger82

    avenger82 Registered

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    That’s probably the reason. When you set 100% pressure you will get it.
    Yeah I meant FFB settings.
     
  2. UGM 133A

    UGM 133A Registered

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    I've yet to try it, but are you saying that if you set it to 100%, it happens at any amount of braking or it happens when you use literally 100% of what the brakes are capable of?
     
  3. UGM 133A

    UGM 133A Registered

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    Ok, so I've tried the car with ultra max braking and yes, it does vibrate quite a lot. That said, when I was doing this, the car was basically uncontrollable, it wouldn't respond to steering inputs and made trail braking impossible. I did a couple of laps around the Nordschleife and found that the vibrations were actually a good cue of what the car was doing under braking so I was able to get just enough brake pressure for every corner. Whether that's realistic or not I have no clue, but it certainly was helpful. So I'm not sure what people are complaining about, it seems like a useful feature to drive fast.

    In a real car with ABS, you can get quite a lot of kickback from the actual brake pedal, which is a good way to know when you're using too much brakes.
     
    Last edited: Nov 1, 2020
  4. Comante

    Comante Registered

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    I still think the source of the vibration is that this car is a road car in term of suspensions , but a race car in term of brakes power and abs settings. The braking power is enough to lock tires, and the suspension are soft enough to lift the Locked tire from the ground, starting a bouncing in the Locked tires. Apparently abs can't let go a Locked tire if the braking power is too much over the grip threshold... and that make sense in a race car.
     
  5. mantasisg

    mantasisg Registered

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    No it does not make sense ^. ABS there is probably just not as aggressive, and leaves a bit of room for a driver to do stuff. Suspensions are very stiff in this car, so I don't think that it is road car specifications. I don't think that it is as much bouncing as just probably effect of larger scrub radius. And softer suspension actually is better to avoid bouncing, stiffer suspension causes bouncing.

    I tried softer suspension at front 180N/mm instead of 200, bit softer bump damping. Also tried neutral front toe and smaller front camber, although not sure if that helps to reduce scrub radius. The vibration seemed bit more gentle, but it could have been placebo.

    Anyway... I am forcing myself to keep on brake pedal pressed hard as front starts to rattle. I don't know what's up about you guys having issue to avoid it...

    I see no big issue about that "braking ffb". The easiest workaround is to somehow tell your foot to ease off the brake as the tires begins to lock up and cause vibrations, you know like you should do it anyway when wheels lock up. Even easier is to reduce braking pressure if you are so terryibly uncomfortable IMO

    By the way pretty fun car. I also drive with H shifter because paddles are broken on my T300. H shifter makes every car more fun lol
     
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  6. benborp

    benborp Registered

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    The thing is, the tyres aren't locking up and the car is quicker if you exploit the benefits of the ABS. It's uncomfortable, but it's quicker.
     
  7. UGM 133A

    UGM 133A Registered

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    Is this something people are doing in the official races? With my driving style it's slower to use full brakes since I can't enter most corners the way I want.
     
  8. Comante

    Comante Registered

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    Maybe shifting brake bias backward you can counter the understeer that come with rattling.
     
  9. UGM 133A

    UGM 133A Registered

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    Does that actually work? If so, how does the ABS function correctly if you can mess with the bias?
     
  10. Comante

    Comante Registered

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    Abs is a passive system , it react to certain input (relative wheels rpm) and apply a output ( release brake pressure) based on a logic (IF THEN ELSE) . Brake bias is simply a valve that change how much pressure goes forward or backward in the brake circuit. Brake bias influence which tire has more chance to lock first, and ABS simply try to avoid it.
     
  11. UGM 133A

    UGM 133A Registered

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    Yeah, but we're talking about using %100 super-duper-max-ultra brakes here. It would already be at the threshold to try and prevent a lockup on any wheels, so I'm not sure if changing the bias rearward should make a difference. Maybe it does in the sim, I'm just saying, it logically doesn't make much sense.
     
  12. mantasisg

    mantasisg Registered

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    This thread goes messier with every post lol

    Are you sure that tires aren't locking up ? Right now I have no proper base to say that they lock up, other than that they feel like they do. Probably over/around 50 percent lockup.

    I suppose it is fastest if you go a bit into that "rattling zone", but I doubt it is good to go deep in it ? But once we had little online go in Nordschleife, I did something like 7'54 or 7'58, and the real fast guy did around 7'20, I think he was sideways everywhere lol
     
  13. benborp

    benborp Registered

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    It absolutely does make sense that brake bias affects the car's balance and retardation even when a car is equipped with ABS.

    Under threshold braking conditions the amount of braking power available to the rear axle, as generally the fronts begin to activate the ABS, will affect weight transfer, balance, the proportion of available grip used for retardation. Under extreme braking, brake bias will influence the relative timing that ABS commences on each axle, which will affect balance.
    Under threshold braking, brake bias is still an important tuning element.

    And the brakes aren't solely used in straight line, threshold braking scenarios. Corner entry balance and mid corner corrections use fine brake inputs to alter weight distribution. There would be no expectation of activating ABS under such circumstances and every desire of having a suitable brake bias to manage that weight transfer effectively.
    Going on feelings and also brake position trace, individual wheel brake pressure traces, individual wheel rotation traces and replay files I'm certain that the tyres aren't locking up. The ABS is doing its job.

    And I'm pretty sure I'm close to getting the best out of the car.
     
    Last edited: Nov 3, 2020
  14. UGM 133A

    UGM 133A Registered

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    Yes, I'm sure it would affect the balance before the ABS is activated. I should have worded what I said differently. What I mean is that, if I don't use full brakes, then I can drive it the way I want, so if I were to move the bias rearward, then I would maybe have better corner entry with 100% braking, but in any other situation I would almost certainly have too much of a rear bias.

    I'm sure running the brakes till they explode is fine in a game, but in reality, no one in their right mind would be using 100% brake pressure in every corner on every lap. You'd destroy the brakes very quickly and then you definitely wouldn't be going very fast.
     
  15. Comante

    Comante Registered

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    I think there is a reason if default setup has brakes setted to 67% instead of 100%: modulability.
     
  16. Tomislav Leskovic

    Tomislav Leskovic Registered

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    I have CSW 2.5 and same problem with strong vibrations when braking. I was testing something in the controller json file and changed streering resistance type to use friction insted of damping. Immediately I've noticed no more wrist braking vibrations while braking...even on 1.0 multiplier and 0 smoothing. Actually, braking finally feels good to me with this change. Can somebody test this and confirm?
     
    Last edited: Nov 5, 2020
  17. marvelharvey

    marvelharvey Registered

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    Didn't work for me sadly.

    Anyone else had any luck with this?
     
  18. UGM 133A

    UGM 133A Registered

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    You'll also not get very realistic FFB with it set to friction. Last time I tested this it made it very difficult to feel subtle slip angles.
     
  19. Tomislav Leskovic

    Tomislav Leskovic Registered

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    Just to be sure...I've changed this value in my saved controller file (for example bmwcs.json) not controller.json and then loaded it once I was in the garage. And yeah there is a diff in how forces are felt compared to damping but was courious why there is no wrist braking forces with friction compared to the damping.
     
  20. UGM 133A

    UGM 133A Registered

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    From what I understand from some explanations years ago when this was still in beta; the friction setting uses mainly (or possibly only?) tire grip/friction to send feedback to the wheel. Whereas the damping uses suspension deflection which is apparently much more realistic. It may be that both settings use a bit of both inputs and each one favors one over the other, I'm not entirely sure.
     

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