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Discussing GT4 in ACC

Discussion in 'ACC General Discussions' started by GONKO, Jul 21, 2020.

  1. bbman

    bbman Racer

    From my understanding, ARB only control the roll (as in: the speed). The ride height defines the roll center and therefore, how much roll occurs.
  2. C#27

    C#27 Gamer

    Anti roll bars are springs not dampers. They do control the amount of body roll (not the speed) by reducing the difference in spring forces between the outside and inside wheel. The spring force, as well as the wheel travel, on the outside wheel gets reduced and added to the inside wheel, which reduces body roll. However, at the same time the anti roll bar increases the difference in wheel loads between the outside and inside wheel, which reduces the overall grip of the corresponding axle. This effect is used when tuning the cars handling at the limit.

    For cars that don't rely on too much aerodynamics, tweaking the ride height can also be used to affect body roll. As explained by Aris in the posted video, the roll center can be moved closer to the center of gravity. With that the roll moment of the axle can be reduced. Because this method reduces the source of the body roll problem, it comes without the drawbacks of the anti roll bar and doesn't reduce the overall grip of the axle. However, the effect of the ride height on the distance between the roll center and the center of gravity is highly dependend on the actual suspension geometry and might not work (well) on every car.
    chksix, AndyK70 and bbman like this.
  3. Cirith Ungol

    Cirith Ungol Simracer

    Hi thanks for your explanation ! It really helped understand what happens in ACC.

    However I don't understand how you can reduce the travel of the spring on the outside tyre while also increasing the load difference ? From my understand if the ARB reduces the spring travel, that energy is sent to the inner wheel and thus the wheel load difference should decrease right ?
  4. bbman

    bbman Racer

    You can decrease the roll motion, but you cannot stop the weight(/load) shift. By decreasing the energy stored in the springs, you're transferring more load from the inside to the outside tyre. Due to the little thing called "tyre load sensitivity", a bigger difference in loads means less traction potential for the axle.

    LATE4APEX Alien

    Interesting reading.

    So I ran a little testing with the Camaro, went from minimum to max rear ride height, and then when from max to min, repeated, and couldn't really confirm much, if any difference.

    My take on that is, as rear ride height influences many different aspects of the cars handling, because of the influence it has on all the different variables involved, being able to determine just what changing the rear ride height has overall, is going to be minuscule, especially as related to the GT4 Camaro.
    For my specific need, to increase top end on the Camaro.

    If I feel like it, I will more testing on long straight tracks, like Monza.
    Last edited: Jan 18, 2021
    FriendOfJah likes this.
  6. Guidofoc

    Guidofoc Alien

    My understanding of the roll bar as a total ignorant is that the roll bar regulates the speed of the lateral weight transfer. With a softer roll bar the car will roll and so the time spent rolling will gradually increase the weight on the loaded side. This slower rate of weight transfer will increase the lateral inertia but will also help the tires "absorb" the weight transfer, avoiding a sudden "push" on the loaded tires that might lose grip. With a stiff roll bar instead the weight transfer is quick and that may unsettle the tires. On the other hand it makes the car more reactive to quick changes of direction so it helps in chicanes etc. Does this make any sense?

    Increasing the ride height (and so the COG) would theoretically increase the roll because the weight moves away from the wheels but as Aristotelis mentioned in the video the change of geometry could actually reduce the lever and so make the roll actually less pronounced. So I gather that ARB is more useful at low ride height?
    Last edited: Jan 18, 2021
  7. C#27

    C#27 Gamer

    That actually explains it quite well. I like to explain it a little more detailed, like follows:
    When cornering, or in general in situations with differing wheel travels between left and right, the anti roll bar comes into play. It acts as a second spring. For each wheel the simplified connection from chassis to the road surface can be seen as:

    chassis > (main) spring > anti roll bar (acts like spring) > wheel (for this explaination we will ignore the wheel stiffness and assume it is a solid body) > road surface

    The basic wheel load without the ARB is induced by the chassis (wheight and weight transfer due to inertia). This component can't be changed. So, as we know, this wheel load is higher at the outside wheel than the inside wheel, which means without the ARB the spring on the outside is compressed further than on the inside.
    Now with the ARB, that connects outside and inside wheel, the outside arm moves up and the inside arm moves down in that secenario. Due to the torsional stiffness of the ARB, the arm on the inside pushes up and increases the spring load as well as the spring travel. But the ARB pushing up between the spring and the wheel also means it takes load away from the inside wheel. That load is transferred to the outside wheel, where the ARB arm pushes down. This decreases the spring load and travel, but at the same time increases the wheel load.

    To a certain degree, yes. But as I wrote above, it is not the only effect. Of course the ARB will influence the transfer behavior, meaning quicker responses with stiffer ARBs. This already goes into great deatail though and is not the main aspect.
    bbman and Guidofoc like this.
  8. kirk heath

    kirk heath Gamer

    I'm limited in setup knowledge but do know, GT4 are much more focused towards mechanical grip rather than aero
    romandevision, PhysaliS and LATE4APEX like this.
  9. Karsten Beoulve

    Karsten Beoulve Simracer

    Sorry to revive the thread, but i'm a mediocre Simracer, very clean albeit slow and I'm about to enter a championship with gt4 cars... I usually just choose the car i feel comfortable with, but this time i would want to give it a more serious shot and get the most performance i can.

    The championship will be on the British gt tracks so Oulton, Donington, Snetterton, Silverstone, Brand's Hatch... I started going around with the Mercedes, but i feel that altoght i feel good in it it's a bad choice; its power and torque seem a bit wasted due to the gearing and I feel it's kind of slow around turns.

    That aside other people in the serie are doing their tests too, well it seems that we'll have a grid with around 20 between Astons and Ginettas, with some occasional odd choiches here and there. My question is, are those cars that much better? Other drivers say that they have over 1 second better pace than the bunch... Is it true?

    Also is the current BOP correct to the actual values and the serie was that single sided? Any suggestions are welcome!
  10. geanito

    geanito Gamer

    I'd say, and people will probably be triggered, that the GT4 BoP is not as good as the GT3 ones.

    There are certain cars that at certain tracks are way faster than others. When it initially came out, I mentioned that for example, the X-Bow GT4 was very slow on both Suzuka and Nurburgring. On Suzuka while other cars would run 2:11 laps, my best lap was a 2:12,5 (and I'm a fairly decent driver). Same would happen on Nurburgring where people would do constantly 2:05 and my laps would always be at 2:06.

    As a example, on the real GT4 race on Nurburgring that car was extremely competitive with both McLarens and Porsches.

    On certain tracks like Zolder and Kyalami, for example, it's a fairly competitive car. The same applies for Snetterton.

    I know for a fact that some cars will do better in some tracks, but IMO, the BoP is not good enough. Also, for some cars, the X-Bow being the one I tested the most, both the safe and aggressive setup are very bad.
    Last edited: Feb 23, 2021
  11. Cirith Ungol

    Cirith Ungol Simracer

    Don't even take the X-Bow if you want something competitive, even with setups the car is utterly trash and doesn't even drive well. I took it for a championship and I was sometimes 2s slower per lap than I'm with the alpine for example.
    Karsten Beoulve likes this.
  12. Karsten Beoulve

    Karsten Beoulve Simracer

    What would be your suggestions after a while championship with gt4, and your opinion on the cars competitiveness?
  13. Cirith Ungol

    Cirith Ungol Simracer

    Best of the best is Aston and Porsche, Aston is easier to drive but may be slower on some tracks. Otherwise AMG and BMW are ok, Audi maybe. It depends on how is your championship designed, if you have no mandatory tyre change then the light cars like Ginetta and Alpine are good because the tyres are like brand new even after 1 hour.
  14. Karsten Beoulve

    Karsten Beoulve Simracer

    Two thirty mins races, second one with reverse grid.

    I ran some test and Mercedes started to get some tires issues after such short races...

    I'm a bit uncertain on what cars to try...
  15. lero

    lero Gamer

    Hmmm you sure about that? Seems to be working just fine...


    I mean sure, maybe it takes more setup work than the average car to get the most out of it and there are some tracks where it simply doesn't have the pace to fight for podiums, but over a season it all balances out. Like it does with just about every single car on the grid.

    KTM takes a whole different driving style but nothing wrong in the way it drives, a fun and rewarding car when you get the hang of it.
  16. Nev Roberts

    Nev Roberts Racer

    Disappointed on completing a British GT Championship in a McLaren gt4 to find no points awarded in the Leaderboard. I realize the GT4 cars aren't quick enough to score points overall but there is a Class option where the points could be shown and they are given after each race. I finished on the podium in all six races but was listed in last place on the leaderboard.
  17. geanito

    geanito Gamer

    Since you're likes the car like me, what are your thougths on the tracks I've mentioned? There are tracks where I'd expect it to perform worst, but not worst to a point where it has no chance at all.

    I find places, like Suzuka, where the cars overtake it on the straights like it was nothing. It's very different for example from Zolder, where the other cars are faster on the straight lines, but not to a point where it is ridiculous.
  18. pankykapus

    pankykapus KS Dev Team Staff Member KS Dev Team

    Depends on the the tracks in the championship, after the first round of the pro tier in the RCI BritGT, it looks like regardless of multiclass the small cars are very competitive around the twisty tracks if you are able to stay ahead. It was a mix of Ginettas, Camaros, BMW, Mclaren, Aston, AMG in top positions.

    This BOP question is a bit overmystified when it comes to rookies or midfield, all the cars are within a second on average, so unless you're in a field full of aliens, your skill will matter a lot more.
    People are not necessarily a second slower in the KTM for example because it hits a wall there but because it is a harder car to drive, so skill differences will be amplified.
  19. Karsten Beoulve

    Karsten Beoulve Simracer

    We would follow the british gt 2019, so Oulton, Snetterton,Donington,silverstone, brands and spa.

    We have 3-4 aliens, 5-6 fast guys, other 8 between fastish to average and a few slow drivers, On a grid of 24 it seems the general consensus is that the cars to go with are the usual suspect.

    Races are going to be 30 mins if it may change the evaluation
  20. chksix

    chksix Hardcore Simmer

    I wonder what the Ginetta would be like with a 7th gear? Possibly OP?
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