Rebound numbers

[doormeister]

I have been playing on the assumption that a lower rebound number means the rebound is providing less resistance, hence the spring will rebound quicker. But in GTVault tuning instructions, it clearly states that with rebound at 2, the shock "will not return as fast.", and with the rebound at 9, the shock " returns the shocks the opposite way fast."

This is not a small discrepancy from what I have read on this forum.

What gives?

 

[Duke]

My assumption aligns with the GTV one, though I didn't realize that they published it as well.

In my experience, you can think of the bound/rebound numbers as the tendency of the wheel to be at its static position. The lower the numbers, the easier it is to displace the wheel and the longer it takes to return. The higher the numbers, the harder it is to displace the wheel and the faster it returns to static position.

Others, such as sukerkin, who have done a large amount of tinkering and theorizing as well, agree with you, however. Lacking any direct input from PD, the question has not been settled for sure.

 

[doormeister]

As soon as I get the tv back, I'll do a brake test: I'll set the front bound at 10, and try the rear re-bound at 1 and 10. One of these should show more noticable pitch forward under heavy braking.

 

[rk]

In my experience, you can think of the bound/rebound numbers as the tendency of the wheel to be at its static position. The lower the numbers, the easier it is to displace the wheel and the longer it takes to return. The higher the numbers, the harder it is to displace the wheel and the faster it returns to static position.

So a setting of 8/1 (bound/rebound) would actually be the stiffest in terms of dampers, right? Fascinating supposition; I have been until this moment a confirmed sukerkinian on the matter but the theory somehow makes sense and might explain some discrepencies I encounter tuning for the big bump on Nürburgring. At 120mph it is difficult to tell if the car is experiencing too much bound, or infinite bound- from too little rebound, as it skews off the road; but I think I can isolate the condition and test it.

 

[doormeister]

I tried to see if I could tell a difference in the way the car body rocked as I accelerated and braked - on rear rebound @ 1 then 10 and back, etc. I really couldn't.

I realized that my acceleration time in the 400m should be better if I load up the rear tires quicker, i.e. faster rebound on the front will bring the hood up quicker and provide more traction as the weight shifts rearward. I consistently got about .02 sec faster on the 400m with the front rebound set at 1 vs. 10. I also went back and forth about 8 times to confirm this. Renault Clio was the test car.

Use it as you wish.

 

[sukerkin]

Thanks for the nods of kudos Duke and RK .

In GT4 there is an even greater cloud of obscurity over what the settings do and what the numbers mean than there was in GT3 !

All the real world tuning 'rules' that I've learned over the years still seem to apply ... most of the time .

Like RK I too have found occaisions on certain tracks with certain cars where I've had to break the rules to get the car to work and it is much harder to tell whether what you've done has actually helped or hindered the handling because, as in RL, any set-up is a compromise so you'll find some corners are better after a suspension change and some are worse : pulls-hair-out : .

A prime example is my notes on setting up a Cerbera for Seoul.

Here is the extract:

"Trying to set her up for Seoul is, er, soul destroying . Can't get her to behave properly; it's as if the streets were diesel slicked.

Messing with the Dampers makes me think that PD have got it slightly wrong. I find increasing the Front Rebound makes corner entry understeer reduce, increasing the Rear Rebound makes corner exit understeer increase and reducing the Rear Bound made exit understeer worse!

Decided that this was an artifact of springs that were too soft for this flat track. Returned to my old rule-of-thumb of the Bound & Rebound adding up to the Spring Rate and got much better, more sensible results from the Dampers."

From that point I went rambling on about how when I tried the same thing at New York it didn't work ...

The idea I'm trying to get across is that nothing is fixed in suspension tuning. Everything is a variable and that comes through in the game. I'm finding, as I twirl more spanners on GT4 cars, that I'm needing to take account of things I could largely ignore in GT3 e.g. drive-train type, the cars 'class' and large variations in tyre characteristics.

As ever, it comes down to the driver/mechanic and their individual style; plus, altho' much vaunted as a simulation, GT4 is still just a game and doesn't model suspension dynamics in real time.

So, if tuning it 'properly' and logically doesn't work, try weird and wonderful stuff and see what happens (including implementing the theory that rather than measuring resistance, as they do in RL, the Damper numbers indicate speed of elastic response).

 

[Duke]

So a setting of 8/1 (bound/rebound) would actually be the stiffest in terms of dampers, right? Fascinating supposition; I have been until this moment a confirmed sukerkinian on the matter but the theory somehow makes sense and might explain some discrepencies I encounter tuning for the big bump on Nürburgring.

That's the theory I developed for personal use while playing GT3. While I don't have the mileage or the tuning experience in GT4 yet, I've seen nothing to change my opinion on the subject yet.

 

[doormeister]

I just recently (hey, I'm new to the game anyway) started focusing more on spring rates to tune in the under/oversteer, and am trying to leave toes at 0 to save tire wear. It seems that spring rates effect under/oversteer more than bound/rebound rates or stabilizer settings. But I'm still learning. thx for your comments.

 

[rk]

I just recently (hey, I'm new to the game anyway) started focusing more on spring rates to tune in the under/oversteer, and am trying to leave toes at 0 to save tire wear. It seems that spring rates effect under/oversteer more than bound/rebound rates or stabilizer settings. But I'm still learning. thx for your comments.

I try to think of the dampers controlling the "transition" between driving straight and being within the realm of the steering bias, i.e.: if I've set my front spring softer to enhance turn in, but the rig wants rotate too far in the transition, I might raise front dampers to make it a little less willing to make the initial turn OR I might return the spring to it's original value and lower the front bound (if after reading from Duke I still know how to do that) to get some but less of an oversteer bias.
So far as toe (and non sliding camber values) go, I have tested extensively and see no evidence that the physics engine supports increased wear for higher numbers. This aligns with my discovery that straight line braking can sometimes be IMPROVED with higher camber (as if the car or set-up has an "ideal" camber).