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Thread: How to pick spring rates? (and how do they interact with Jussi's calc?)

  1. #1
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    How to pick spring rates? (and how do they interact with Jussi's calc?)

    As a default, in the old days, I played car games so obsessively that I could change the spring rates to match weight distribution f-r, tweak for balance and then adjust everything else around them. I played so much I was consistent and would know that it was the cars behaviour changing rather than my hamfisted inputs.

    After a 3 year break I'm not what I would describe as consistent. This means that for the moment I cannot differentiate with any certainty between my mistakes and the inherent behaviour of a given setup. I am faster in rwd racing cars with the TC and SC on. This tells me I'm terribad atm.

    With that in mind there is no point in me spending huge amounts of time fiddling with a setup because I just won't be able to spot the details amongst the background noise of my own crapness.

    With that in mind I would at least like to know that I have a reasonable base setup for a given vehicle. As jussi has said elsewhere (yes I have been using the search function ) if a car deals with bumps consistently and in a neutral fashion at one track it will probably be ok elsewhere.

    Spring rates and arb settings are the starting point for this and I have no clue with this game atm. Please don't stone me for mentioning this but in games like forza and gt up to 2012 you could make realistic setups and they would work to a point but at the extreme range of adjustment you could find some quirky stuff that should not work but was much faster.

    #2. When I have those set I am being thick and struggling to understand which set of settings (street, stiff race and where the hell should my red lines on the graph be in relation to the pretty blue and orange ones?) that are generated by jussi's calc I should go for. Yes I can and probably will go through each iteration and compare in a lengthy testing process but any pointers or hints that can be given would be appreciated.

    Right, back to nur gp and that bloody merc. Thanks for any replies and not pointing and laughing too much.

    Controller: xbox one controller and all assists off.

    Gibbon

    Edit to add: Looking at jussi's calc and what I have read elsewhere here I am aiming at a frequency difference front to rear of about 15% ish with a bias to the front. Is that a reasonable starting point?
    Last edited by Gibbon; 04-10-2015 at 11:34.

  2. #2
    WMD Member Jussi Viljami Karjalainen's Avatar
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    With pCARS and some other games (ISI engine based games for example can do this as well, it's up to the developers/modders whether they make use of it or not) there's an important thing to remember when working with springs (and dampers): How the car behaves is dependent on the wheel rates (spring rate measured at the wheel), but the setup gives you direct spring rates. In most cases you can not use the numbers in the setup to account for things like weight distribution etc. because without knowing the motion ratios of the suspension you can't really know what the effective spring rates are. Hence why the calculator is so nice to have.

    When I pick springs I generally go with a few basic things: Overall frequency and front to rear bias. Overall frequency is essentially the "stiffness" of the suspension, and is comparable even between cars with different weight. If two cars have the same suspension frequency, then spring wise they're pretty much equally stiff, even if the springs and weights themselves are very different. Higher frequencies mean stiffer suspensions, and stiff suspensions can give you some benefits but tend to hurt mechanical grip, so keep in mind the performance level of the car when setting it up. Road cars don't tend to benefit from going far past 2 Hz, you start to need better tyres and more DF to get significant improvements. Better tyres and higher DF lands you somewhere in the 3-4 Hz range where GT3 cars live for the most part. Again added DF and better tyres like in prototypes takes you further into the 4 Hz ranges, and top spec open-wheelers and LMP1 cars can well live in the 5 Hz regions. And if you're on a track where you don't need or get much DF (a very slow track for example with really slow corners) you can lower the frequencies to increase mechanical grip. Likewise in rain, softer suspension that increases mechanical grip tends to help quite a bit.

    The front to rear bias is about the under/oversteer bias of the car. A higher front bias increases understeer tendencies, a higher rear bias increases oversteer tendencies. Essentially the stiffer end tends to have less grip potential, so stiffening up the front reduces grip there = understeer, and vice versa. 15-25% higher front frequency is a good starting point, and seems common in real race cars as well. You have a fairly stiff front end to provide a stable aero platform and quick steering responses, and a slightly softer rear end to allow the suspension to squat easier on acceleration, increasing traction. You can obviously set it however you wish, for example the Z4 GT3 by default has the balance much closer to equal which makes it a really nippy and agile car in twisty sections (though a bit hairy when you stray over the edge at times).

    Dampers are largely an individual thing, but staying between the blue lines usually puts you into a good place. I prefer my dampers to be quite rebound biased (I want minimum amount of disturbances when going over bumps), so I usually aim for the stiffer line in rebound and somewhere in the middle of the two lines with bump. Though really I use the total damping force at 3 in/s readouts below the graph, I usually aim my rebounds to 80%, my front bump to 50-55% and rear bump to 45-50%. Like with the springs I prefer my rear bump damping slightly softer to increase traction. Fast damping I want in the 30-40% range for all of them, if at all possible.
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  3. #3
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    Thanks Jussi. That clarifies what I was pretty certain of and makes sense of stuff that I had no idea on. I know you've said similar in other posts but now it's all in one place for my tiny little mind to grasp. Thanks for taking the time to repeat yourself.

    Gibbon.
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  4. #4
    Superkart Pilot
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    There is a calculator? Please pm me a link!!

  5. #5
    GT5 Pilot inthebagbud's Avatar
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    Quote Originally Posted by tclancey View Post
    There is a calculator? Please pm me a link!!
    Look under the tuning section in the Resources Thread

    http://forum.projectcarsgame.com/sho...rces-for-Pcars
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  6. #6
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    Quote Originally Posted by tclancey View Post
    There is a calculator? Please pm me a link!!
    A linky to the dl can also be found in Jussi's sig. Two posts above yours.
    The following user likes this Post: Jussi Viljami Karjalainen


  7. #7
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    Hey Jussi, I have some related questions that I think you can probably help me with if you don't mind? First, what is the difference in handling between a car that has, say, a really front biased spring stiffness (understeer) which is cancelled out by having a rear biased anti-roll bar (oversteer) setup, and a car that has a neutral spring setup and neutral anti-roll bars? In steady state corning that both have same neutral balance. Or to put it another way, if I had a car that understeers I have two options: soften the front springs/stiffen rear springs, or soften front roll bar/stiffen rear roll bar. Both changes will cure the understeer, but how do you decide whether it's the spring balance you should adjust or the roll bars?
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  8. #8
    WMD Member Jussi Viljami Karjalainen's Avatar
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    There are several things that'd play into it: Really stiff springs, and sway bars, can reduce mechanical grip significantly, and especially can affect how progressive the grip behavior when losing grip is. So if you have a car that has very stiff front springs and very stiff rear sway bar to compensate, you're removing grip potential from both ends, and at the rear specifically you're also making the suspension less independent (sway bars by their nature lock the left and right side together to some extent, reducing lateral independence). You could even get issues with the inside rear tyre lifting in some situations. So you could well end up in a situation where the car suffers from both sudden understeer and snap oversteer when encountering disturbances. There aren't too many reasons you'd want excessively stiff springs/sway bars at one end specifically, unless you're limited in your tuning somehow. Like for example some autocross series mandate that you must use stock springs, so some of their damper and anti-roll bar settings can look really insane because they're compensating for something they'd rather adjust but can't.

    EDIT: Essentially, between two cars that had the same total roll resistance bias but where one has stiff front springs and stiff rear sway bar vs. a car with more neutral overall settings, the first car could end up feeling much more touchy and inconsistent in its behavior, without really providing any benefits.
    Last edited by Jussi Viljami Karjalainen; 26-10-2015 at 17:06.
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    My road car OEM style setups (updated occasionally when I find new info) over at P.CARS Setups Database

    My Suspension Calculator spreadsheet for Project CARS v1.3.5.2 - Updated on 16.10.2016!

    Suspension Calculator now available on the P.CARS Setups Database website!

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  9. #9
    Superkart Pilot
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    Thanks Jussi. I guess what I really want to figure out is when to tweak the balance between the front and rear roll bars, and when to tweak the balance of the springs. Both would affect the balance of the car everywhere. I'm trying to figure out a more methodical approach to tuning them both rather than just doing laps, tweaking things, running more laps...ad infinitum.

  10. #10
    WMD Member Jussi Viljami Karjalainen's Avatar
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    Generally I'd say a good rule of thumb is to not try to compensate for one thing with another, but trying to align everything in a similar way and just changing how deep you go with it. For racing cars I generally set everything for a slight front bias in everything, slightly higher front frequency, roll-bias slightly to the front, slightly stiffer front dampers (critical rates, not absolute values). If I feel the car is too understeery I adjust for a lower front bias in everything instead of adjusting only one thing. Though with small enough changes you might not actually need to adjust more than one setting, the rest still staying within range. When you're doing things blindly it can be best to do things one at a time in small steps, but I have enough trust in my calculator after using it for a few years that I generally trust it to adjust springs, dampers and sway bars simultaneously and not bork things up (it hasn't so far). With the old blind approach I've seen many a setup end up in a situation where the springs are oversteery but that's compensated by the dampers being understeery, which is countered by the sway bars being oversteery, which is countered by the alignment being understeery, which is countered by the aero being oversteery... You get the idea. Establish a solid baseline first and then work in small increments, and if possible try to keep the setup coherent between the different aspects so you don't end up with a car that does one thing in one situation and another in some other situation.

    EDIT: Of course this depends also on what you're looking for with the setup. Doing a realistic road car setup for example throws much of this out the window, because for comfort reasons the springs are usually set up with a significantly high rear bias, often in the 20-30% higher frequency range, so the front ARBs tend to be much beefier to compensate for it and provide some understeer, as is the alignment. Almost all road cars have higher camber at the rear for increased rear lateral grip, so far I know of only some very sporty or extreme cars that have either close to identical alignment front and rear or even more aggressive alignment at the front. One example is the McLaren 12C, which has -1.5 degrees at the front and -1.0 at the rear, but it gets away with this because of the Z-bar rear suspension. The Z-bar is like the anti-roll bar, increasing spring rate in heave but not doing anything in roll, so the car ends up having a higher rear frequency in straight line bumps (more comfortable) but a higher front frequency during cornering (tends towards understeer).

    And there's a good reason why racing cars most often have stiffer front ends: It makes the front end response sharper and provides a more stable aero platform for the front wing/splitter. The softer rear suspension on the other hand allows the car to squat more smoothly during acceleration, increasing traction. The basic setup does tend somewhat towards understeer, but the power and grip of the racing car helps, as does the ability to use really aggressive front end alignment and aerodynamics balancing, adjustable brake bias, differential settings, etc. etc.
    Last edited by Jussi Viljami Karjalainen; 27-10-2015 at 22:30.
    CPU: Intel i7 2600K @ 4,6 GHz | GPU: Gigabyte GTX 770 4GB Windforce 3 | MOBO: ASUS P8P67 Pro | RAM: 4 x 4GB Kingston HyperX DDR3 1600 | Sound: ASUS Xonar U7 | PSU: NZXT HALE90 650W 80+ Gold | OS: Win8 x64 | Wheel: Thrustmaster T500 RS GT wheel/pedals, Logitech G25 shifter | Monitor: 2x23" IPS-LCD 1920x1080 60Hz & 42" 1920x1080 60Hz | SpeedTest | PingTest | PingTest to UK
    Sim history: IndyCar Racing I & II, F1GP2, Grand Prix Legends, Sports Car GT, Richard Burns Rally, GT Legends, Race/GT-R Evolution/Race On/etc., RaceRoom Racing Experience, SimRaceWay, Live For Speed, netKar Pro, Assetto Corsa, rFactor 1 & 2, among others...

    My road car OEM style setups (updated occasionally when I find new info) over at P.CARS Setups Database

    My Suspension Calculator spreadsheet for Project CARS v1.3.5.2 - Updated on 16.10.2016!

    Suspension Calculator now available on the P.CARS Setups Database website!

    Next Gen = More Biscuit!
    The following 3 users likes this Post: donpost, Pfalzdriver, Schnizz58


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