Ride Height and Roll Center

[eg6_dude]

When playing GT4 yesterday, and tuning my car I noticed in the text( I normally don't pay any attention to most of the text! ) that when you lower the ride height the game suggests to change the spring rate to a higher rate. Does anybody know if GT4 takes into account suspension geometry, roll center, or instant center,etc.? Does the suspension travel stay the same or change when lowering? ( is the supension spring perch adjusting along with the ride height to keep the travel the same?) Does the racing suspension automatically change any of those adjustments or other unlisted settings?

If not then besides geometrical changes in the suspension components, why would the spring rate change from lowering the car?

( I know there are many different kinds of suspensions which react differently to suspension under compression and rebound Just looking for general answers.)

Also while I'm on the subject of changes during suspension strokes. Does GT4 take into account changes in camber, toe, or caster? Does it take caster into account at all?

sorry about the complexity and variety of questions asked. Just pondering Needing some help while pondering!👍

,thanks in advance for answers!

 

[Scaff]

When playing GT4 yesterday, and tuning my car I noticed in the text( I normally don't pay any attention to most of the text! ) that when you lower the ride height the game suggests to change the spring rate to a higher rate. Does anybody know if GT4 takes into account suspension geometry, roll center, or instant center,etc.? Does the suspension travel stay the same or change when lowering? ( is the supension spring perch adjusting along with the ride height to keep the travel the same?) Does the racing suspension automatically change any of those adjustments or other unlisted settings?

If not then besides geometrical changes in the suspension components, why would the spring rate change from lowering the car?

( I know there are many different kinds of suspensions which react differently to suspension under compression and rebound Just looking for general answers.)

Also while I'm on the subject of changes during suspension strokes. Does GT4 take into account changes in camber, toe, or caster? Does it take caster into account at all?

sorry about the complexity and variety of questions asked. Just pondering Needing some help while pondering!👍

,thanks in advance for answers!

From my own testing sessions that GT4 does to a degree take into account different suspension systems and the characteristics they should display. For example spring rate vs. wheel rate is almost certainly a factor and personally I do feel that changes in ride height have an effect on roll centre locations.

Its however very difficult to 'prove' that, as you get no 'hard' telemetry data from GT4 in these areas, so a lot of my observations are based on 'feel' and comparisons to real world applications and experience.

Its certainly easier to bottom out most cars if you lower the ride height too much without adjusting the spring rates, also spring rate as a factor against sprung weight is also a factor.

In regard to camber and caster, these do play a factor in suspension travel, but I have long suspected that this occurs in simply a 'pre-programmed' manner rather than actually using the arc of the suspension travel for each and every car (and every suspension upgrade). With caster, certainly in previous versions of the series is has been present as a 'hidden' value, its just a shame we can't adjust it, as that would certainly help the drifters here in regard to some of the issues they can have with self-centring.

The changes that occur when you move from one suspension upgrade to the next (aside from the obvious firming up of the default values) do appear to indicate a slight stiffening of natural system itself. This I have personally always taken to be an attempt to show a change from rubber to poly mounts and the use of rose-joints in the system, etc.

Overall I personally hope to see both a huge increase in the detail of suspension (and other tuning areas - active diff tuning would be nice as an option) set-up and upgrades; combined with a much more details set of telemetry tools.

Regards

Scaff

Edited to add - this thread may be of interest.

https://www.gtplanet.net/forum/showthread.php?t=81176

 

[eg6_dude]

You obviously know more about suspension then I do.

However my understanding of roll center was that the roll center could not change unless the inner or outer pivot points of the suspension were altered to change to the angle of the peice that makes up the points ( for example on a double wishbone suspension raising the upper arm's outer pivot point would change the roll center). When lowering the ride height the suspension pivot point's position stay statonary and the whole supension just compresses upwards, so therefore the roll center couldn't change under compression because the pivot point position have never been moved or altered, could it?

If so then lowering the ride height in GT4 would change the instant center and increase camber gain, wouldn't it?

(hope I used the right terms and you(scaff) understand what I mean.)

 

[Scaff]

You obviously know more about suspension then I do.

However my understanding of roll center was that the roll center could not change unless the inner or outer pivot points of the suspension were altered to change to the angle of the peice that makes up the points ( for example on a double wishbone suspension raising the upper arm's outer pivot point would change the roll center). When lowering the ride height the suspension pivot point's position stay statonary and the whole supension just compresses upwards, so therefore the roll center couldn't change under compression because the pivot point position have never been moved or altered, could it?

If so then lowering the ride height in GT4 would change the instant center and increase camber gain, wouldn't it?

(hope I used the right terms and you(scaff) understand what I mean.)

You don't have to physically move the inner or outer pivot points of the suspension to change the angle of the control arms (if we use double wishbone as an example), as while the outer mounting points (at the wheel) will not move, as the tyre can't start to levitate, the actual height of the inner mounting points may (depending on suspension type) change physical height when we increase or decrease the cars ride height, which will alter the control arms angle relative to its previous position.

Source - http://members.aol.com/sccacuda/cars/5SmthTa.html


If you take a look at the above diagram you will see that if we were to raise the cars height and the inner mounts also move upwards, then the control arm angle would change and the roll centre move upwards (and obviously the reverse would be true as well).

For a real world example the picture below (of a front monoshock unit on a Formula Renault) you can clearly see that if the cars ride height (via the pushrod length) was altered then the control arm angle would be altered as its length does not vary. Now the Formula Renault does not allow for a great deal of adjustment in ride height, so the changes would be minimal, but it does illustrate it quite well.



However what has to always be kept in mind with all of this is that if calculation of the static roll centre can be a pain (it can even be below ground level), keeping track of it dynamically is even more difficult to predict.

You are right that in GT4 changes in ride height would have an effect on the instant centre (and by that a change in the roll centre height) and camber gain, but as for how well and how accurately it may or may not be accounted for, well that's far more difficult to judge.

Regards

Scaff