Tuning Damper Bound/Rebound

Discussion in 'GT3 Tuning' started by Stoffy69, May 15, 2003.

  1. Stoffy69


    The problem I had with understanding damper behaviour was to confuse the stiffness of the suspension (controlled by the springs) with the effect of the dampers which control the rate at which the springs compress/decompress. When tuning dampers you should always be thinking in terms of weight transfer.

    Dampers control the rate of weight transfer in an accelerating/deccelerating car. For example, a braking car wants to pitch its weight forwards, onto the front springs. The rate at which it is allowed to do this is controlled by the front damper bound (FB) and rear damper rebound (RR). If a fast FB setting is used the car will be allowed to pitch it's weight forwards more rapidly under breaking ie. there is more weight on the front springs than the rear. If all springs are equally stiff this will mean that the front tyres have more grip than the rear tyres, causing the back end of the car to swing out (oversteer/unstable/drift). A fast RR setting must also be used to allow the car to rapidly take it's weight off of the rear springs and transfer it to the front. On the other hand, if you use slow dampers the weight will not transfer to the front as quickly under breaking and the weight will be more evenly distributed between front & rear springs/tyres, stabilising the car (understeer/stable/racing).

    Looking at the opposite behaviour, an accelerating car tries to pitch its weight rearwards, onto the rear springs. The rate at which it is allowed to do this is controlled by the rear damper bound (RB) and front damper rebound (FR). In this case using fast settings the weight is transfered quickly to the rear springs/tyres and the rear has more grip than the front, giving stable turning (understeer). Fast settings mean more grip at the front than the rear (oversteer).

    I believe that a high numerical setting in GT3 will produce rapid damper behaviour in the bound stroke, but slow movement in the rebound stroke. I will do some testing and post again to confirm - there seems to be considerable confusion on this point, especially since the in-game advice is misleading/incorrect. I assume that the physics engine of the game is sound and that it is therefore possible to extract fast rebound from the dampers in some way (which may or may not mean higher numerical settings).

    I anyone else wants to try this out i suggest testing a car with very soft springs, a high ride height and a lot of power. Use rapid braking and accelerating and watch the movement of the car body during replays (forwards/rearwards pitch).
  2. Duke

    Duke Staff Emeritus

    United States
    Well, hello there, stranger! Welcome to GTPlanet. Nice to see a new face posting something besides "yo need settings for gtone road car" or "how do i set my Trueno up to drift like Initial D". Please join in the discussions and share your knowlege.

    I have to disagree with you on the point you make above, however. I've found that higher numbers relate to stiffness, or resistance of the wheel to being displaced. In other words, high numbers make a given wheel slow to compress away from its original position, and fast to rebound back to its original position. Others may disagree with me, but that's my take on it after doing some of my own research a few months ago.

    Again, welcome aboard, and lets hear some of your racing stories on the Writeups board!
  3. Stoffy69


    Yeah, to be honest i need to do some testing myself to figure the numbers out for sure.

    Do you agree with my explanation of the oversteering/understeering?
  4. Duke

    Duke Staff Emeritus

    United States
    Yes, basically I do agree, within the confines of what I wrote above. I will say that adjusting Bound seems to have slightly more effect than Rebound, but the two do need to work in concert.
  5. mattmac83


    Great topic of discussion! I wish I could contribute to your findings, but I don't have the time at the moment. I'm *just* starting to really get into fine-tuning and learning as much as I can. I'd love to hear about what you find with bounds and rebounds. Good luck, and keep us informed!
  6. Stoffy69


    Okay well i've done a little testing and came up with the following:

    To induce oversteer into corners (deccelerating):

    FB Level 10
    RR Level 1

    To induce understeer into corners (deccelerating):

    FB Level 1
    RR Level 10

    To induce understeer out of corners (accelerating):

    RB Level 1
    FR Level 10

    To induce oversteer out of corners (accelerating):

    RB Level 10
    FR Level 1

    This is always true, as far as I can gather from the behvaiour of my car (RUF CTR2). This does however seem to contradict my weight transfer ideas. Look at deccelerating oversteer. By using high front bound settings you are making the suspension stiffer at the front and decreasing the speed of weight transfer onto the forward springs. Hence you are spreading the load more evenly between the two sets of tyres. I would have said that this would give you a stable, understeering car but the opposite is true!!

    I have read some other posts which suggest that by increasing the load on a tyre you decrease it's efficiency could this explain the behaviour? To be honest i think there's a balance somewhere between loading a tyre usefully to provide grip and overloading it in a horizontal direction which reduces grip but it's all a bit complex and I'd appreciate someone who knows what they are talking about to explain it all to me.
  7. Nightmage82


    what does the first setting do (the suspesion stiffness is it? the kg/m one) i thought setting THAT lower makes it stiffer and higher makes it softer, i rarely do much about the bound and rebound because i dont know what they do, but thanks for that stoffy, will try it out, and welcome to gtplanet :p
  8. sukerkin


    Hi Stoffy69

    From my experiences in the game, you're on the right track with treating the dampers as opposed pairs e.g. Front Bound works in conjunction with Rear Rebound.

    However, in one of those wonderful contradictions that a game like GT3 can throw up, your conclusions on how to attain a given cornering effect with the dampers are exactly the reverse of mine :D!

    As we've both hinted at, generally speaking, it is easiest to think of the Bound and Rebound as cross-matched pairs, one pair of which affects corner entry and the other pair corner exit.

    I don't know if I'm telling you stuff you're already aware of, so forgive me if I am, but the four major cornering conditions and their Damper related solutions are as follows:

    To correct Corner Entry Oversteer: Soften Rear Rebound and/or Stiffen Front Bound

    To correct Corner Entry Understeer: Stiffen Rear Rebound and/or Soften Front Bound

    To correct Corner Exit Oversteer: Soften Front Rebound and/or Stiffen Rear Bound

    To correct Corner Exit Understeer: Stiffen Front Rebound and/or Soften Rear Bound

    These modifications are in relation to either the starting default settings or a default damper array you decide on for yourself (for example, I generally put Bound to 5/5 or 6/6 and Rebound to 8/8 or 9/9 straight away and then modify to suit from there).

    The effects of too much Rebound aren't really noticeable as long as both ends of the car are balanced but too much Bound will markedly reduce grip and cause tyre scrub; conversely, too little Bound will make the car unresponsive so it usually requires a bit of experimentation to find out what range of values a car is happiest with.

    It might simply be that differences in driving style mean that individual drivers will come to widely varying solutions regarding how to get the effect they want in the cars handling. It'll be interesting to see how your research progresses.
  9. graveltrap


    United Kingdom
    Wow my first post :D

    A easy way to bench mark your damper settings. Set rebound to lowest level (1) Set bound to lowest level (1) go do some laps. Increase bound 1 adj at a time until the car becomes overly harsh or starts skating. Bound bench mark found!

    Then increse rebound until the "soft feel" of the suspension is removed.

    You've now bwnch marked your dampers :D

    Small adjustments can then be carried out to tweak the handling.

    Remember the dampers account for the last 20-30% of performance so you need to get spring rates etc set up first!

    Info came from a race drive and full details are somewhere on the web sorry can't remember where.

    When tried this technique shaved around a second off of a lap round deep forest (AE 86 SS edition on sim tyres, 220bhp lightweight stage 3, close ratio box).

    Hope this is of some use!!
  10. Stoffy69


    I think you are over-simplifying here mate, when you say that increasing bound reduces grip. Oversteer is caused by too much grip on the front tyres and too little at the rear, so that the rear swings out when turning. Understeer is caused when you have more grip at the rear than the front, since the car wants to go in a straight line under these conditions.

    I find that very understeering settings cause a lot of scrub under acceleration on the front tyres, but the rears are okay. Oversteering settings tend to even out the tyre wear between front and rear.