a method of tuning a car from scratch

Discussion in 'GT4 Tuning' started by nomis3613, Apr 23, 2010.

  1. nomis3613

    nomis3613 Premium

    Messages:
    831
    *** UPDATE ***
    Improved guides for
    - FF cars
    - FR cars
    have been made. Guides for other drivetrains are planned (one day!).

    My original post is here, but a lot of my theories have changed since his was written.

    *** /UPDATE ***
    I've been working on a tuning method to extract maximum speed. Have a read, try it out and let me know what you think. Yes, this is similar to a previous thread of mine, I've tried to put the tuning tips into a “start-from-scratch” method this time.

    The guide is incomplete (and always will be...unless I get to speak to Polyphony physics programmers...), these are the areas I'd like to improve in the future (suggestions welcomed):
    - LSD tuning for AWD cars, I really don't know what I'm doing here (in a rear-biased setup, so the front axle be higher so that the rear wheelspins first, or should it be softer to allow the car to pivot better? )
    - should dampers be set to suit spring stiffness?
    - brake balance controller- see here
    - downforce vs tyre wear
    - the difference between damper bound and rebound for response to bumps
    - using spring rates to change overall balance (instead of just stabilisers).

    --------------------------
    STEP 0: RAMBLE
    Tuning is a balancing act, where speed gained in one area is often balanced by speed lost in another. And each handling problem can be “solved” by various fixes, each of which has a different side-effect. For example, power understeer can be reduced with negative rear toe, stiffer rear stabilisers, softer front stabilisers, negative front toe, more front downforce, etc etc. But which method is the best? This method aims to find the best handling setup for a car, not only in front to rear balance, but also in maximising grip by trying to avoid “2 wrongs make a right”.

    To keep the guide brief, I'll use a fair bit of car tuning jargon. If you don't understand something- please don't be afraid to ask, I'm happy to explain even the most basic question. Also, the guide is purely written for GT4 so when I say “this works like this...”, I mean for (my understanding of) GT4, which may or may not be the same as real-world physics.

    Tuning is an iterative process, so there is no correct order. Try to focus on the questions in each section, and ignore the rest of the handling characteristics. But there are times you will need to a) fix something drastically wrong before you can continue tuning (eg add rear downforce if the car is totally unstable at high speed) or b) go back and tweak a previous setting because you have changed something else which has a related effect (eg reduce front toe after stiffening the rear stabiliser). So feel free to jump around the steps, but I believe this order is a good starting point.


    -------------------------------
    STEP 1: NEUTRAL SETTINGS
    These settings are a good 'neutral' starting point to help you tune:
    brake balance: 3, 3
    spring rate, ride height: 1/2 way
    dampers: 4, 4, 4, 4
    toe: 0, 0
    camber: 0, 0
    stabilisers: 1, 1
    driving aids: 0, 0, 0
    LSD: minimum
    VCD: minimum
    downforce: 0, 0


    -------------------------------
    STEP 2: CAMBER
    Most tuning involves trading grip between front and rear tyres etc, however the camber angle is unique because it determines the maximum potential grip for the tyre. Setting the wrong camber angle is just throwing away speed! The camber angle is the first thing to be tuned, so that we're starting off with the maximum possible grip from the tyres.

    Tyres have an optimum camber angle to produce the most grip. In GT4, this angle is the same for all 3 types of grip (cornering, acceleration, braking), which makes tuning much easier. The optimum angle for the rear tyres is 0.5 deg less than the front tyres. Sport tyres have an optimum angle (for the front tyre) between 2-3 degrees, compared with 1.5-2 degrees for the front tyres.

    The simple method is just use 1.7 front and 1.2 rear for racing tyres; and 2.5 front and 2.0 rear for sport tyres. This will be somewhat near the optimum angle.

    For those who want the absolute best speed possible, time-consuming testing is needed within the above ranges. The best way is using braking distances (cornering takes too long and acceleration tests are too much affected by launch revs and shift points). On the twin ring circle track, measure the braking distance (using the data logger) as you brake from 200 to 100km/h. Actually, brake from 210km/h to 80km/h but only measure the 200-100 section; this will give more reliable results. Try to brake in roughly the same place on the track each time (on a flat section of the straight), but don't it's not critical. After each test, increase the camber by 0.2 and try again (I told you this was time-consuming!). Work your way through the rear camber angles first, then repeat for the front.


    -------------------------------
    STEP 3: GEARING
    This is hard to explain, so I'll just describe a method which works for most cars, instead of delving deep into theory. Decide what maximum speed you want (remembering that higher max speed = less acceleration). Move the top gear slider all the way to the right, then adjust the final drive until this speed is achieved at maximum revs in top gear. Set 1st and 2nd gears all the way left, then space out 3rd, 4th and 5th gears evenly in between.

    If a gear is causing wheelspin at low revs, then the ratio can be moved left without reducing acceleration, this will allow the other gears to be spaced closer together for better acceleration. For each track, the gears which are used most should be spaced as tightly as possible. For example if a track mostly uses 3rd and 4th gears: set 3rd as far left as possible and 4th as far to the right. Often 1st gear is only used for standing starts, because it just results in wheelspin for slow corners.


    -------------------------------
    STEP 4: BODY ROLL, DIVE UNDER BRAKES
    This is where the real handling tuning starts. Choose a track to be your testing venue- I like Apricot Hill for its mix of corners, but it is up to you. Now you will start pounding out laps, making small changes and testing the difference. First step is body roll...

    I believe that body roll does not affect grip in GT4, so spring settings are mainly used to suit how the driver likes the car to feel. Drive around your testing venue (yes, the grip of the untuned car may be doing strange things, but try to ignore them- we are not worried about understeer/oversteer/etc for the moment) and focus on these questions during turning and braking (how the car feels over bumps and kerbs will come later):
    “does the nose dive too much under brakes” > needs stiffer springs
    “does the car feel too sharp and twitchy” > softer springs
    “does the car feel too soft and floaty” > stiffer springs

    At this stage, use the same spring rates front and rear.

    Rant about ride height: Overall ride height is pretty useless in GT4. Lower heights do not result in more grip (despite what the scrolling text says) and body roll/dive under brakes is only affected by spring rates. Unless your car is bottoming out and producing sparks (I've only ever seen the Le Mans and F1 cars do this) then there is no reason to change the ride height. Personally, I set the ride height to be the opposite of spring rate (eg if springs are at 25% of max stiffness then the ride height is 75%) but this is out of superstition alone! The only real use for ride height is if a rear- or mid-engined car is too unstable, using lower front ride height than rear will push the weight forward and make the car more stable.

    -------------------------------
    STEP 4: DRIVING OVER BUMPS
    Now concentrate on how the car behaves over bumps and kerbs
    “does the car feel harsh and lose lots of grip over bumps” > decrease all 4 dampers equally
    “does the car feel too floaty over bumps” (very rare) > increase all 4 dampers equally
    To avoid extreme damper settings when tuning the dampers, the springs can also be adjusted in the same method.

    -------------------------------
    STEP 5: FRONT TOE
    The first time you will think about whether the car is under/oversteering. Like the scrolling text says, front toe is the trade off between initial turn-in and maintaining front grip later in the corner.
    “does the front end lose grip after the apex” > decrease front toe (to higher negative values)
    “is there not enough turn-in, but too much front grip exiting a corner” (very rare) > increase front toe
    The feeling for this is hard to explain: it's basically a lumpy feeling as the front end gains and loses grip through the corner: one moment you're following the desired line with plenty of front grip, then suddenly the car starts to understeer, then if the corner is really long the grip will come back again.


    -------------------------------
    STEP 7: BRAKE BIAS
    The brake controller adjusts the “reserve” grip (left over for cornering) during braking
    “is the car too easy to spin while braking” > increase front brake and reduce rear brake
    “is the car too hard to turn while braking” > reduce front brake and increase rear brake

    Don't set any of the brakes above 12. If you need settings more extreme than this, there is probably something else wrong with the tuning anyway.

    -------------------------------
    STEP 8: BRAKING WEIGHT TRANSFER
    Concentrate on how the car feels as you first hit the brakes, especially if you are already turning at the time. As the weight moves forward under braking, this can be controlled by the front bound and rear rebound dampers.
    “is the car too unstable when you start to brake” > increase the front bound or rear rebound
    “does the car refuse to turn when you start to brake” > decrease the front bound or rear rebound

    This all sounds similar to the brake controller from the last step, so what's the difference, right?! Hard to say! The dampers are more about the initial weight transfer at the start of braking, while the brake balance has greater effect towards the end of the braking. In the end, the effect of brake bias and weight transfer are so similar that the best setup will be determined by making sure the tyre wear is the same for front and rear tyres. However, If the car is RR, the braking weight transfer is usually the cause of the problem so try this first.

    As for whether you should stiffen the front or rear, this is a change to use the side-effect to your advantage. If you have been thinking that the car is understeering (so needs a stiffer rear) then stiffen the rear bound or rebound instead of the front (vice versa for oversteering).


    -------------------------------
    STEP 9: ACCELERATION WEIGHT TRANSFER
    Think about what happens as you accelerate out of a corner.
    “does the car understeer when you start to accelerate” > increase front rebound or rear bound
    (note: the difference between this and front toe is that front toe deals with understeer that occurs even when not accelerating (ie mid corner). Acceleration weight transfer deals with how acceleration causes the front tyres to get “lighter” (and lose grip) as the weight moves rearwards)
    For FF only “does the car oversteer when you start to accelerate” (very rare) > decrease front rebound or rear bound
    For all other cars (than FF), it is likely that any exit oversteer is caused by the engine torque, not the lack of weight transfer; it is better to fix this using LSD settings than dampers.


    -------------------------------
    STEP 10: 4WD TORQUE SPLIT
    The VCD controls the amount of torque going to the front wheels. Changes to the LSD settings will mean you should look at the VCD again.
    “do you get wheelspin coming out of tight corners” > increase VCD
    (note: if the car is very overpowered and all 4 wheels are spinning, VCD cannot help)
    “does the car understeer when accelerating out of 3rd gear corners” > reduce VCD
    Tuning 4wd cars is another level of complexity and possibilities. I prefer to set the car up as mainly RWD (less turn-in but power oversteer on exit is possible), but it is also possible to set the car like a FWD (more turn-in, power understeer on exit) if you like that feeling. If you prefer the feeling of typical FWD then set the VCD to max before Step 3.


    -------------------------------
    STEP 11: OVERALL UNDERSTEER / OVERSTEER
    I know it's been hard to ignore the basic balance of the car through the previous steps, but finally you get to fix it! Actually, I find that most cars are well balanced once the above problems are removed so only minor tweaks are needed here.
    “does the car oversteer in general” > stiffen front stabiliser
    “does the car understeer in general” > stiffen the rear stabiliser or decrease the rear toe (higher negative numbers)
    note: stiffer stabilisers causes more grip loss when 1 wheel hits a bump, so use as little stabiliser as possible

    It is also possible to tune the overall balance with the spring and damper rates but I prefer to use just the stabilisers (so that springs can control bumps / initial weight transfer and the dampers look after the weight transfer). However any extreme settings can have strange side effects, so if a car needs max front stabiliser and min rear (or vice-versa) to be balanced, then I would change the spring rates so that less extreme stabiliser settings can be used. Spring rates are the wrong way around in GT4: stiffen the front or soften the rear to cure understeer (opposite for oversteer). This means that softening the rear could be a good way to cure understeer in a rwd car, because the softer rear will also reduce wheelspin when accelerating.

    What about using downforce to adjust the balance?? We'll get to that later...


    -------------------------------
    STEP 12: LSD
    Higher settings reduce wheelspin (as long as only the inside wheel is spinning, it can't help if engine power is enough to spin both wheels), but they also reduce the cars ability to pivot (ie turn). So you only use as much LSD as you need to control the wheelspin.

    ALL CARS
    “does the car feel unstable and spins easily, especially at the start of braking” > increase initial or decel
    “is the car hard to turn, despite good grip balance” > decrease initial or decel

    RWD CARS
    “does the car wheelspin of oversteer when accelerating” > increase initial or accel

    FF CARS
    “does the car wheelspin when accelerating” > increase accel
    (note: it is difficult to tell when you have too much LSD accel on FF cars, but it will cause increased understeer. So slowly increase the accel until you have enough)

    4WD CARS
    This is complex! (and I don't understand it properly...) If you are using a low VCD setting, only increase the accel or initial on the rear, or the front only if the VCD setting is high. You can (and will probably need to...) play with the LSD and VCD settings for hours until you find the perfect combination.

    (all cars) As for whether you should change the initial or the accel/decel, consider whether you would like the car to be more stable (increase initial) or easier to turn (decrease initial) in general, as well as the effect you are looking for. If so, change the initial, but if you are happy with the stability / ease-of-turning and just want to fix your secific problem, then just change the accel / decel. Keep in mind that using accel / decel will cause the car to change behaviour as you brake / accelerate, so it is better to use higher initial settings and less accel and decel. That way, the car is more consistent in all phases of cornering.


    -------------------------------
    STEP 13: DOWNFORCE
    Now that the handling is balanced, the downforce is the last thing to tune (to avoid “2 wrongs make a right” tuning).
    Set the front downforce to maximum. The car will be very easy to spin, especially at high speed. Increase the rear downforce until the handling feels balanced again.

    If the downforce has reduced the top speed too much, reduce the front downforce and repeat the tuning of the rear downforce.
     
    Last edited: Oct 8, 2010
  2. DK

    DK Premium

    Messages:
    13,430
    Location:
    Ireland
    nomis3613, you've yet again proven that not all New Members spew out incomprehensible rubbish. :tup:
     
  3. Parnelli Bone

    Parnelli Bone Premium

    Messages:
    10,448
    Location:
    United States
    Yea, no kidding. Where have you been hiding the entire past year or so? +Rep.

    It'll take awhile to read all this and digest it, as usual. :lol:
     
  4. RacecarBMW

    RacecarBMW

    Messages:
    725
    Location:
    Canada
    Thank you im going to try this it helps a lot
     
  5. BlacqueJacques

    BlacqueJacques

    Messages:
    3,509
    Location:
    Canada
    Thanks.
    Also greatful for the specifc tunes that are shared out there :tup::bowdown::bowdown::bowdown:
     
  6. nomis3613

    nomis3613 Premium

    Messages:
    831
    haha, thanks for the support guys!

    Yeah, I got impatient waiting for GT5, so I went back to GT3 and now GT4. Hope you find the guide helpful, I'm keen to hear your thoughts.

    Had a scary moment last night, just after posting my guide I was reading the thread discussing whether toe settings were backwards in GT4 (ie toe out is positive). So I did a quick test and found -4 rear toe = oversteer (but not much). So I don't have to rewrite the guide after all, phew!

    Also I was reading Scaff's thoughts on brake balance, where he talks about optimum brake balance to minimise stopping distance. However my philosophy remains that brake balance is a good way to fix entry understeer. I think car balance is more important than straight line stopping distance on a race track, I would happily give away 0.5 metres in stopping distance to have a car nicely set up as I turn in to the corner. </rant>

    I promise it won't be another year before I make another post! :)
     
  7. -MOPAR-

    -MOPAR-

    Messages:
    38
    I just tuned a 240sx using this method and it runs the nurburgring almost 20 seconds faster now.
     
  8. metalslugger5

    metalslugger5

    Messages:
    12
    Ok now that's what I'am talking about!!
    Congratulations for posting this info.
    Trying it right now!!!
     
  9. oldmodelt

    oldmodelt

    Messages:
    1,273
    Location:
    United States
    As a noob to tuning, I found your guide to be short and sweet. Helps me to start to understand this complex (but enjoyable) subject.
     
  10. Parnelli Bone

    Parnelli Bone Premium

    Messages:
    10,448
    Location:
    United States
    You're a noob to tuning? Seems like you been around here for ages. :confused:
     
  11. nomis3613

    nomis3613 Premium

    Messages:
    831
    Thanks heaps for all the positive comments!

    If you disagrees with something in it, I'm very keen to hear- I won't take it personally!!

    Simon
     
    Last edited: Apr 30, 2010
  12. nomis3613

    nomis3613 Premium

    Messages:
    831
    Guide updated!

    Basically I've said that ride height is useless and made a wishlist of stuff I'd like to understand better.
     
  13. sukerkin

    sukerkin

    Messages:
    2,063
    It is ever good to see that even these many years on people are coming into the orbit of GT and using their brains to try and figure out how best to tune cars in a way that does not include fitting Stage 4 Turbos and R5 Tyres :D.

    Much has been written on the subject across many sites (some of it by myself) but it is always interesting to see someone elses thoughts.

    One point to make is that Ride Height is not a useless variable. Whilst we can only guesstimate the influence it has, there are some circumstances in which it has a major effect for it works to position the Roll Centres in relation to the track surface.

    It seems to be of more particular effect on unstable MR vehicles I confess but in my work on the Lancia Stratos, for example, I only started to make real progress once I sorted out the Ride Height.

    https://www.gtplanet.net/forum/showpost.php?p=3375095&postcount=404
     
  14. Leonidae@MFT

    Leonidae@MFT Premium

    Messages:
    5,302
    Location:
    Finland
    Ride height adjustment is far from useless. I admit that the effect is pretty small, but it is there.
     
  15. Greycap

    Greycap Premium

    Messages:
    5,589
    Location:
    Finland
    The "optimal" camber angle doesn't exist. Straight line needs as little camber as possible, higher values increase grip in fast corners and decrease it in slow ones. The "half a degree" rule simply doesn't work as even changing the stabilizers can throw the camber adjustments completely out of whack when the body roll changes and so does the tyre contact patch under cornering.

    Body roll most definitely does affect cornering, as does ride height. As small changes as 5mm of ride height can make a second of difference on one lap because the body roll begins to overwhelm the tyres' threshold. Alternatively a car set too low won't roll enough, the weight transfer to the outside tyres is inadequate and the car understeers into the kitty litter as the outside tyres won't get the bite they need to turn the car.

    The brake balance controller isn't that simple either. Your tips on it would work in real life but this is GT4 which leads to weird things at times. I've seen cars, quite a few of them, that have shorter braking distances using lower values and get better turn in with high front, low rear values. Don't ask why, there's no logical explanation, but it happens.

    LSD settings are a tougher nut that you think. As a very basic principle, yes, lower values mean more manoeuvrability but that's not where it ends. Some cars need more Accel to clear corners by power oversteer, some need more Decel to keep the tail following the front under trail braking instead of being "dead weight" cutting inside the arc drawn by the nose and causing understeer. And using high Initial, less Accel and Decel to maintain the same attitude throughout the corner... no. Just no. It won't work unless you make it fully locked of fully open. You do realize that you're implementing the same setting under extremely differing forces being applied to the LSD? It's fully customizable for the very reason that you can adjust it for the desired behaviour without the need for a "jack of all trades, master of none" setting.
     
  16. Parnelli Bone

    Parnelli Bone Premium

    Messages:
    10,448
    Location:
    United States
    Bottom line (as I think I said in some other thread), nothing is ever set in stone. If lots of camber adjustment or changes in ride height (or whatever) works with one car, it's not guaranteed to work with another, even if both of them have the same drivetrain, same approximate weight, same body style/class etc etc etc...
     
  17. nomis3613

    nomis3613 Premium

    Messages:
    831
    Thanks for the comments!
    Actually I said overall ride height. Yes, changing the ratio of front to rear ride height can be used to tweak the handling. I often do this for unruly MR/RR cars.

    Are you sure this applies to GT4, not just real life? I'm not saying I disagree with you, but if you had any testing to support this, I'd be keen to see it.

    As for real life dynamics, (all other things being equal) a lower car will handle better because there is less weight transfer to the outside tyre.

    I have found that listening to the tyres in straight line stops helps heaps. From comparing the sounds to measured stopping distances I reckon there are 3 situations possible during braking
    1 no wheel slip (no screeching)- increasing the strength will reduce stopping distance
    2 some wheel slip (smooth screeching)- it is in this region of brake strength that shortest stopping distance occurs
    3 too much wheel slip ("jagged" screeching)- the ABS is kicking in to avoid lock-up so stopping distances are longer and you need to reduce the strength

    But a lower accel will cause more power oversteer (for rwd). It is easier to spin up the inside wheel (lower accel) than both wheels (higher accel).

    As for the initial setting, I understand the real life physics, but this is GT4. In my experience using high accel or decel values unsettles the car as you change between accelerating, coasting and braking. I don't have any numbers to back this up, but I tune 1 setting at a time to isolate the effect of that setting.
    PS thanks again for your comments, it is great to get another perspective!

    Amen, also each driver prefers a different feel, which is probably the biggest variable!
     
  18. nomis3613

    nomis3613 Premium

    Messages:
    831
    Hi folks,
    Thanks to help from many people on this site, my understanding of tuning has improved (well, I hope it has!) since my original post. Many thanks to the GTPlanet folks who have helped by sharing their knowledge, you know who you are but if you would like a specific mention, just let me know! Also, I now believe that the method of tuning is highly dependent on the car's layout. So, allow me to present the updated
    FF Tuning Guide

    Edit Oct 2013: Revised text in blue
    --------------------------
    STEP 0: RAMBLE
    This method aims to find the best handling setup for a car, not only in front to rear balance, but also in maximising grip for all situations by trying to avoid “2 wrongs make a right”.

    Tuning is an iterative process, so there is no correct order. Try to focus on the questions in each section, and ignore the rest of the handling characteristics. But there are times you will need to a) fix something drastically wrong before you can continue tuning (eg add rear downforce if the car is totally unstable at high speed) or b) go back and tweak a previous setting because you have changed something else which has a related effect (eg reduce front toe after stiffening the rear stabiliser). So feel free to jump around the steps, but I hopefully this order is a good starting point.

    The defining characteristic of FF tuning is front grip on corner exit. Those poor front tyres are being asked to accelerate and steer at the same time, so getting this balance right is crucial.

    -------------------------------
    STEP 1: INITIAL SETTINGS
    Let's start with these settings. They could well make the car handle worse than the default settings, but they are a good starting point to help identify tuning effects as your setup takes shape.
    brake balance: 3, 3
    spring rate, ride height: 1/2 way
    dampers: 3, 3, 3, 3
    toe: 0, 0
    camber: 1.0, 0.7 (sports tyres) or 2.0, 1.5 (racing tyres)
    stabilisers: 1, 1
    driving aids: 0, 0, 0
    LSD initial: 0, LSD accel: 10, LSD decel 0
    downforce: 10, 0


    -------------------------------
    STEP 2: GEARING, REAR BRAKE & FRONT TOE
    2a GEARING
    Gearing is hard to explain, so I'll just describe a method which works for most cars, instead of delving deep into theory. Decide what maximum speed you want (remembering that higher max speed = less acceleration). Move the top gear slider all the way to the right, then adjust the final drive until this speed is achieved at maximum revs in top gear. Set 1st and 2nd gears all the way left, then space out 3rd, 4th and 5th gears evenly in between.

    If a gear is causing wheelspin at low revs, then the ratio can be moved left without reducing acceleration, this will allow the other gears to be spaced closer together for better acceleration. For each track, the gears which are used most should be spaced as tightly as possible. For example if a track mostly uses 3rd and 4th gears: set 3rd as far left as possible and 4th as far to the right. Often 1st gear is only used for standing starts, because it just results in wheelspin for slow corners.

    There is a method called the "tranny trick" which uses the auto setting to produce better gear ratios than is normally possible. It takes a while to explain and there are differing opinions on what it actually is, so if you are interested in this trick, search for other threads about it.

    2b REAR BRAKES
    At the same time as you're refining gear ratios, the rear brake strength can be tuned. Increase the rear brake strength until you can hear quick repeated chirping noises as you brake hard (instead of a constant screech). Then reduce the strength slightly so the screeching is constant.

    Often, such a high brake strength makes the brakes too "grabby" (especially using a hand controller eg Dual Shock 2), so you will want to reduce the strength anyway. But it is still useful to know what strength is the maximum before the ABS kicks in, because it is useful to know how close you are to this maximum strength and also what the front/rear brake balance is. We'll come back to brakes later...


    -------------------------------
    STEP 3: LSD ACCEL
    Increase the LSD accel until wheelspin only occurs when both wheels are spinning (headphones make it easier to hear whether one or both wheels are spinning).

    Even once you have enough LSD accel by this test, try increasing it more, because sometimes higher LSD accel has positive "side-effects" on handling.


    -------------------------------
    STEP 4: GENERAL UNDERSTEER/OVERSTEER BALANCE
    - If the car understeers, use -ve rear toe
    - If the car oversteers, use +ve rear toe
    This is just a rough method to get the balance in the ballpark so that tuning can progress, we'll fine tune it later.



    -------------------------------
    STEP 5: FRONT CAMBER & FRONT BRAKE
    STEP 5a: FRONT CAMBER
    Find the camber angle which gives the best acceleration using 0-400m testing. Just for this test, use TCS of at least 3 (increase it if the car hits the rev limiter)and AT. Hold full throttle from the start of the timer, then you will get exactly the same time between runs. Increase the front camber angle until you find the angle which gives the lowest 400m time (note: in some setups 0.0 will give the best time).

    The gains to be found using camber are minimal. Increase a degree or two if banked corners are important, otherwise the values above will be fine. See https://www.gtplanet.net/forum/showthread.php?p=8811231#post8811231

    STEP 5b: FRONT BRAKE
    Repeat step 6b for the front brakes.


    -------------------------------
    STEP 6: REAR CAMBER
    The best rear camber angle can be found by testing braking distances. On the twin ring circle track, measure the braking distance (using the data logger) as you brake from 200 to 100km/h. Actually, brake from 210km/h to 80km/h but only measure the 200-100 section; this will give more reliable results. Try to brake in roughly the same place on the track each time (on a flat section of the straight), but don't it's not critical. After each test, increase the camber by 0.2 and try again (unfortunately this is very time-consuming!).
    The gains to be found using camber are minimal. Increase a degree or two if banked corners are important, otherwise the values above will be fine. See https://www.gtplanet.net/forum/showthread.php?p=8811231#post8811231


    -------------------------------
    STEP 7: FRONT TOE
    In an FF car, +ve front toe often gives better acceleration (straight line) traction and -ve front toe often gives better exit grip (this is a simplification, and not always true). So, if the car has wheelspin out of slow corners, try using +ve front camber. Otherwise, try some negative front camber (the effect of this varies though).


    -------------------------------
    STEP 8: SPRINGS AND RIDE HEIGHT
    *disclaimer: it is also possible to tune front/rear balance using the springs and ride height, but my personal preference is to use other settings for this*

    Adjust the front and rear spring rates together (ie keeping the f/r ratio the same), to find a balance between
    a) less grip lost over bumps and better feel for the weight transfer (by feeling the car rotating) > softer springs
    b) minimising body movement when brakes/accelerator/throttle is applied > harder springs
    Note that it is ok to have the car "too stiff", if it doesn't affect your cornering speeds. So don't worry about crashing through bumps if they aren't in an important place on the track. On the other hand, stiffer springs can increase wheelspin and late-corner understeer


    Once the spring rates are set, lower the ride height (front and rear heights should be the same) until "strange" handling effects are noticed. If you are seeing sparks from the back of your car (use the overhead camera) then the car is definitely too low, but also be aware that the car can be too low even if it isn't sparking.


    -------------------------------
    STEP 9: STABILISERS & LSD DECEL
    STEP 9a: STABILISERS
    If the car still has body roll but you don't want to stiffen the springs any more, increase the stabilisers instead. However, stiff stabilisers may increase grip loss over bumps (theoretically moreso than stiffer springs), increased wheelspin and increased exit understeer.

    STEP 9b: LSD DECEL
    Like the scrolling text says, increasing will make the car more stable (also less agile) under braking. Increase this value and see how you like it, personally I find LSD Decel is usually best left at minimum for FF cars.


    -------------------------------
    STEP 10: LSD INITIAL
    As well as changing the car's direction of momentum during cornering, the car must also rotate (eg you were looking eastwards before the corner, now you are looking southwards). If the car does not rotate enough, it will understeer. If the car rotates too much, the tyres have "bitten off more than they can chew" (ie the yaw angle is higher than the grip of the tyres can maintain), so the car will keep varying between gripping and sliding throughout the corner.

    Adjust the LSD initial until you are happy with the balance between rotation and steering response. Note that LSD initial also adds to the effect of LSD accel and decel, so you might like to go back and reduce these settings afterwards.


    -------------------------------
    STEP 11: BRAKES (YES, AGAIN!)
    If the brakes feel too "grabby", reduce the brake strength (often, the balance of the car coming into a corner is more important than the actual stopping power). For a car that has entry understeer, try reducing the front brake strength. Reduce the rear brake for a car that has entry oversteer.


    -------------------------------
    STEP 12: DAMPERS
    Experiment with increasing/decreasing all the dampers by the same amount to work out your overall damping strength. Then tweak the handling as follows (note: sometimes settings will not have the desired effects because dampers are complex, so you'll need to experiment)
    - curing entry understeer: soften front bound and/or stiffen rear rebound
    - curing entry oversteer: stiffen front bound and/or soften rear rebound
    - curing exit understeer: soften front rebound and/or stiffen rear bound
    - curing exit oversteer: stiffen front rebound and/or soften rear bound

    On bumpy tracks:
    - softer bound means the suspension will compress to absorb the bump (which is good)
    - stiffer bound means the suspension doesn't compress, instead the whole car raises with the bump (which is bad)
    - softer rebound means that after the crest of the bump, the suspension will extend so that the tyre stays on the road (which is good)
    - stiffer rebound means that the wheel will hang in the air after the bump (which is bad)


    -------------------------------
    STEP 13: REAR TOE
    Fine-tune the overall balance of the car by re-adjusting the rear toe. Use more negative to cure understeer, or more positive to cure oversteer. If this is not enough to cure the oversteer, try reducing rear ride height and/or adding ballast to the front of the car. If the problem is understeer, try increasing rear ride height and/or adding ballast to the rear of the car.


    -------------------------------
    STEP 14: DOWNFORCE
    Now that the handling is balanced, the downforce is the last thing to tune (to avoid “2 wrongs make a right” tuning between suspension and downforce).
    Set the front downforce to maximum and the rear to halfway. If the car understeers (especially at higher speeds), reduce the rear downforce. If the car oversteers (especially at higher speeds), increase the rear downforce.

    If the downforce has reduced the top speed too much, reduce the front downforce and repeat the tuning of the rear downforce.

    Hope this helps! Feel free to comment/criticise/question.
     
    Last edited: Oct 27, 2013
  19. Temetias.

    Temetias.

    Messages:
    366
    Location:
    Finland
    The FF guide works. It just works. Accomplished great results with it (thanks to nomis, KMW will soon have it's first FF tune) ;)

    Great work! :tup:
     
  20. nomis3613

    nomis3613 Premium

    Messages:
    831
    Many thanks to the GTPlanet folks who have helped by sharing their knowledge, you know who you are but if you would like a specific mention, just let me know! Anyway, onto my new

    FR Tuning Guide

    Edit Oct 2013: Revised text in blue
    --------------------------
    STEP 0: RAMBLE
    This method aims to find the best handling setup for a car, not only in front to rear balance, but also in maximising grip for all situations by trying to avoid "2 wrongs make a right".

    Tuning is an iterative process, so there is no correct order. Try to focus on the questions in each section, and ignore the rest of the handling characteristics. But there are times you will need to a) fix something drastically wrong before you can continue tuning (eg add rear downforce if the car is totally unstable at high speed) or b) go back and tweak a previous setting because you have changed something else which has a related effect (eg reduce front toe after stiffening the rear stabiliser). So feel free to jump around the steps, hopefully the order below is a good starting point.

    Settings that are together in one step can be tuned simultaneously to save time.

    IMHO a well-tuned FR car should be stable (unlike MR and RR which can have lift-off oversteer, etc), yet use the engine to generate power oversteer so that cornering can be adjusted with the throttle.


    -------------------------------
    STEP 1: INITIAL SETTINGS
    Let's start with these settings. They could well make the car handle worse than the default settings, but they are a good starting point to help identify tuning effects as your setup takes shape.
    brake balance: 3, 3
    spring rate, ride height: 1/2 way
    dampers: 3, 3, 3, 3
    toe: 0, 0
    camber: 1.5, 1.0 (sports tyres) or 2.5, 2.0 (racing tyres)
    stabilisers: 1, 1
    driving aids: 0, 0, 0
    LSD initial: 5, LSD accel: 5, LSD decel 5
    downforce: 0, 0


    -------------------------------
    STEP 2: GEARING & REAR BRAKE
    2a GEARING
    Gearing is hard to explain, so I'll just describe a method which works for most cars, instead of delving deep into theory. Decide what maximum speed you want (remembering that higher max speed = less acceleration). Move the top gear slider all the way to the right, then adjust the final drive until this speed is achieved at maximum revs in top gear. Set 1st and 2nd gears all the way left, then space out 3rd, 4th and 5th gears evenly in between.

    If a gear is causing wheelspin at low revs, then the ratio can be moved left without reducing acceleration, this will allow the other gears to be spaced closer together for better acceleration. For each track, the gears which are used most should be spaced as tightly as possible. For example if a track mostly uses 3rd and 4th gears: set 3rd as far left as possible and 4th as far to the right. Often 1st gear is only used for standing starts, because it just results in wheelspin for slow corners.

    There is a method called the "tranny trick" which uses the auto setting to produce better gear ratios than is normally possible. It takes a while to explain and there are differing opinions on what it actually is, so if you are interested in this trick, search for other threads about it.

    STEP 2b REAR BRAKES
    At the same time as you're refining gear ratios, the rear brake strength can be tuned. Increase the rear brake strength until you can hear quick repeated chirping noises as you brake hard (instead of a constant screech). Then reduce the strength slightly so the screeching is constant.

    Often, such a high brake strength makes the brakes too "grabby" (especially using a hand controller eg Dual Shock 2), so you will want to reduce the strength anyway. But it is still useful to know what strength is the maximum before the ABS kicks in, because it is useful to know how close you are to this maximum strength and also what the front/rear brake balance is. We'll come back to brakes later...


    -------------------------------
    STEP 3: LSD ACCEL
    Increase the LSD accel until you are no longer getting wheelspin on just one wheel when exiting tight corners (headphones make it easier to hear whether one or both wheels are spinning).

    Even once you have enough LSD accel by this test, try increasing it more, because sometimes higher LSD accel can improve the handling.


    -------------------------------
    STEP 4: REAR CAMBER AND TOE
    STEP 4a: REAR CAMBER
    Find the camber angle which gives the best acceleration using 0-400m testing. Just for this test, use TCS of at least 3 (increase it if the car hits the rev limiter)and AT. Hold full throttle from the start of the timer, then you will get exactly the same time between runs. Increase the front camber angle until you find the angle which gives the lowest 400m time (note: in some setups 0.0 will give the best time).

    The gains to be found using camber are minimal. Increase a degree or two if banked corners are important, otherwise the values above will be fine. See https://www.gtplanet.net/forum/showthread.php?p=8811231#post8811231

    STEP 4b: REAR TOE
    - If wheelspin is a problem, try using positive rear toe.
    - Otherwise, use rear toe to adjust the overall balance. Use positive toe if the car oversteers, use negative toe if the car understeers.



    -------------------------------
    STEP 5: FRONT CAMBER & FRONT BRAKE
    STEP 5a: FRONT CAMBER
    The best front camber angle can be found by testing braking distances. On the twin ring circle track, measure the braking distance (using the data logger) as you brake from 200 to 100km/h. Actually, brake from 210km/h to 80km/h but only measure the 200-100 section; this will give more reliable results. Try to brake in roughly the same place on the track each time (on a flat section of the straight), but don't it's not critical. After each test, increase the camber by 0.2 and try again (unfortunately this is very time-consuming!).

    The gains to be found using camber are minimal. Increase a degree or two if banked corners are important, otherwise the values above will be fine. See https://www.gtplanet.net/forum/showthread.php?p=8811231#post8811231

    STEP 5b: FRONT BRAKE
    Repeat step 2b for the front brake.


    -------------------------------
    STEP 6: DAMPERS
    If the rear toe is set to avoid wheelspin, I try to use dampers as the main method to tune out understeer/oversteer. Experiment with increasing/decreasing all the dampers by the same amount to work out your overall damping strength. Then tweak the handling as follows (note: sometimes settings will not have the desired effects because dampers are complex, so you'll need to experiment)
    - curing entry understeer: soften front bound and/or stiffen rear rebound
    - curing entry oversteer: stiffen front bound and/or soften rear rebound
    - curing exit understeer: soften front rebound and/or stiffen rear bound
    - curing exit oversteer: stiffen front rebound and/or soften rear bound

    On bumpy tracks:
    - softer bound means the suspension will compress to absorb the bump (which is good)
    - stiffer bound means the suspension doesn't compress, instead the whole car raises with the bump (which is bad)
    - softer rebound means that after the crest of the bump, the suspension will extend so that the tyre stays on the road (which is good)
    - stiffer rebound means that the wheel will hang in the air after the bump (which is bad)
    If you still have an oversteer problem, try reducing rear ride height and/or adding ballast to the front of the car. If the problem is understeer, try increasing rear ride height and/or adding ballast to the rear of the car.


    -------------------------------
    STEP 7: SPRINGS AND RIDE HEIGHT
    *disclaimer: it is also possible to tune front/rear balance using the springs and ride height, but my personal preference is to use other settings for this*

    Adjust the front and rear spring rates together (ie keeping the f/r ratio the same), to find a balance between
    a) less grip lost over bumps and better feel for the weight transfer (by feeling the car rotating) > softer springs
    b) minimising body movement when brakes/accelerator/throttle is applied > harder springs
    Note that it is ok to have the car "too stiff", if it doesn't affect your cornering speeds. So don't worry about crashing through bumps if they aren't in an important place on the track. On the other hand, stiffer springs can increase wheelspin and late-corner understeer


    Once the spring rates are set, lower the ride height (front and rear heights should be the same) until "strange" handling effects are noticed. If you are seeing sparks from the back of your car (use the overhead camera) then the car is definitely too low, but also be aware that the car can be too low even if it isn't sparking.


    -------------------------------
    STEP 8: STABILISERS & LCD DECEL
    STEP 8a: STABILISERS
    If the car still has body roll but you don't want to stiffen the springs any more, increase the stabilisers instead. However, stiff stabilisers may increase grip loss over bumps (theoretically moreso than stiffer springs), increased wheelspin and increased exit understeer.

    STEP 8b: LSD DECEL
    Like the scrolling text says, increasing this will make the car more stable under braking. Increase this value and see how you like it (the effect varies from car to car). Sometimes LSD decel has similar effect to front toe (see Step 10), so keep this in mind.


    -------------------------------
    STEP 9: LSD INITIAL
    The basic theory of LSD initial is that higher values make the car harder to turn, but the benefit is that more LSD effect can be used to prevent wheelspin. However there are often other effects in GT4 and it varies car-by-car, so experiment with half and maximum values.

    I find that sometimes LSD initial improves turn-in while you are accelerating, so to take advantage of this you'd need to brake early, then accelerate before the apex


    -------------------------------
    STEP 10: FRONT TOE
    In an FR car, front toe is often the balance between turn-in and exit understeer. Negative front toe increases front grip during corner exit (eg less understeer) but also reduces turn-in. Positive front toe does the opposite. Concentrate on whether the car has too much turn-in or exit understeer to tune front toe.

    Note that front toe and LSD decel can sometimes have a similar effect, so it is worth revisiting Step 8b to find the optimum balance between these front toe and LSD decel.


    -------------------------------
    STEP 11: BRAKES (YES, AGAIN!)
    If the brakes feel too "grabby", reduce the brake strength (often, the balance of the car coming into a corner is more important than the actual stopping power). For a car that has entry understeer, try reducing the front brake strength. Reduce the rear brake for a car that has entry oversteer.


    -------------------------------
    STEP 12: DOWNFORCE
    Now that the handling is balanced, the downforce is the last thing to tune (to avoid "2 wrongs make a right" tuning between suspension and downforce).
    Set the front downforce to maximum and the rear to halfway. If the car understeers (especially at higher speeds), reduce the rear downforce. If the car oversteers (especially at higher speeds), increase the rear downforce.

    If the downforce has reduced the top speed too much, reduce the front downforce and repeat the tuning of the rear downforce.


    All comments and suggestions for improvements are welcomed!
     
    Last edited: Oct 27, 2013
  21. Temetias.

    Temetias.

    Messages:
    366
    Location:
    Finland
    I've been waiting to see this for a while! :) Looks good and I'm most certainly going to try this guide. :tup:
     
  22. Rotary Junkie

    Rotary Junkie Premium

    Messages:
    9,809
    Location:
    United States
    The ideas you've thrown into my head here are resulting in tons of abuse to my poor Mazda6 hatch. Drag tuning showed 0.0 front camber to be the best for straight line traction, however, skidpad and track testing showed that said camber angle harms cornering capability, so I'm starting to think again that there's no "magic" number for grip to be found with camber tuning.

    Currently my skidpad abuse has resulted in a ~4km/h gain from mild tweaks (60-64km/h start to finish) in the last 45 minutes or so. Hoping to hit my arbitrary goal of 70km/h but I doubt it's possible.
     
  23. nomis3613

    nomis3613 Premium

    Messages:
    831
    Cool! I'm looking forward to hearing your thoughts.

    Glad to hear it's helping! Don't show that Mazda any mercy!!

    Skidpad? Skidpad???? Is there really a skidpad in GT4?
    This is something I've been longing for, a skidpad opens up a whole new world of testing options :drool:. Where is it?

    Yeah, my approach to camber could well have some major changes soon, it will probably end up being very similar to what you are saying.
     
  24. Rotary Junkie

    Rotary Junkie Premium

    Messages:
    9,809
    Location:
    United States
    Gymkhana. It's under Driving Park. No timing and no replay but you've got a lot of flat ground and a lot of cones to bash.
     
  25. nomis3613

    nomis3613 Premium

    Messages:
    831
    That's fantastic, thanks heaps!!!

    Just wondering, what method do you use to record your speed? Are there any tricks to hold a constant radius circle so that you can compare between settings?
     
  26. Rotary Junkie

    Rotary Junkie Premium

    Messages:
    9,809
    Location:
    United States
    Off to the left of the starting point there's two circles marked out by cones. Push the car as hard as you can without hitting any of the outside cones, stabilize speed, there you go.
     
  27. GTP_roadrunner

    GTP_roadrunner

    Messages:
    640
    Thanks nomis for you well written guides. Now I surely will get a more understandeable entry into the tuning secrets.

    Much appreciated,
    Seb.
     
  28. nomis3613

    nomis3613 Premium

    Messages:
    831
    You're most welcome, Roadrunner, glad to hear it helps.

    Just curious, are you using it for GT4 or GT5?
     
  29. GTP_roadrunner

    GTP_roadrunner

    Messages:
    640
    I´m intended to use it for gt5, since regarding from what I have read about it, I´d say basics should be the same. It just reads nicely for me and shows how tuning components affect each other. I´ll let you know about the results :)
     
  30. nomis3613

    nomis3613 Premium

    Messages:
    831
    Following some testing, I've updated the FF guide and FR guide. If anyone is still reading this, I'd be keen to hear your thoughts!