Is Suspension Tuning Backwards? - A Test with RX-8

[nos2]

Well, it's bee a few months since my last post, but I've come to the conclusion that for most cars, the reverse spring rate tuning method works. I tune most of my cars with higher front spring rates and it does induce oversteer at medium to high speed, but it seems like at low speed I do get more understeer. So like sukerin said, there maybe somethings that needs to be calculated in real time that was replaced by a fixed aproximated value.

 

[Scaff]

Well, it's bee a few months since my last post, but I've come to the conclusion that for most cars, the reverse spring rate tuning method works. I tune most of my cars with higher front spring rates and it does induce oversteer at medium to high speed, but it seems like at low speed I do get more understeer. So like sukerin said, there maybe somethings that needs to be calculated in real time that was replaced by a fixed aproximated value.

Can I just ask, do any of these cars have a wing fitted?

I only ask because that has a major effect on balance at mdeium to high speed, to such a degree that suspension balance becomes irrelivent and aero balance becomes dominant.

I would personally disagree in regard to 'reversed' tuning for anything les that extreme settings.

Softening an end (relative to its current setting or the opposite end) increases grip to a degree, after which extreme settings cause havoc with the grip. This actually has many real world parallels, as it throws cars onto the bump stops (or worse fully compreses springs) and creates a highly mobile roll centre.

Spring rates alone are also very missleading, as the damper rates (particularly bound and rebound on FC suspension) can have a huge impact on how quickly a corner or end loads up or releases load. All of which can again have a massive effect on balance.

In my opinion (and it is just my opinion) the entire 'reversed spring rates tuning' principal is an over simplistic theory applied to a very complex subject.

I know full well that some may take offense at that, but to be honest I would stand by it. Incremental tuning of suspension balance has always reacted in accordance to the 'basic' rules of real world suspension tuning, including the negative/unexpected effects of extreme settings.

Previous GT games have let us get away with some very dodgy set-ups, particularly in regard to the relationship between the front and rear roll centres, load transfer and the use of extreme settings.

Regards

Scaff

 

[nos2]

Some of my cars have wings and some don't. Most of my drift cars do have wings tho. But I usually leave the downforce at 0 and I only use downforce after I can't get the feel I want (mostly for drift cars) from suspension alone. I would agree that the tuning is not completely reversed. But from my own experience, in most cars and in most circumstances, increasing the front spring rate and damper rate will increase the front grip and induce more oversteer.

 

[Scaff]

Some of my cars have wings and some don't. Most of my drift cars do have wings tho. But I usually leave the downforce at 0 and I only use downforce after I can't get the feel I want (mostly for drift cars) from suspension alone. I would agree that the tuning is not completely reversed. But from my own experience, in most cars and in most circumstances, increasing the front spring rate and damper rate will increase the front grip and induce more oversteer.

Ok so the wing issue aside, you say when you increase the front spring and dampers, which then raises a number of other questions, such as:

• by how much?
• did the rear change at all?
• what about the differences between bound and rebound?
• did you leave the anti-roll bars unchanged?
• toe & camber?
• ride height, is it level or not?
• as you are drifting what about LSD set-up?

We also get into issues then about exactly when this is occuring, at what point in the corner - turn-in? entry? mid? constant radius/throttle? exit?

All of these factor have a huge roll to play in the overall balance of a car, as they are linked in a manner that simply can't be avoided.

What I am basically saying is that I do not believe that GT4 spring rates are reversed for tuning, more that it is very easy to forget about the other factors working on the car.

Regards

Scaff

 

[nos2]

by how much?
usually 30-50% higher than stock

did the rear change at all?
usually 10-20% lower than stock

what about the differences between bound and rebound?
usually I keep the bound a rebound the same. (ie if I increase the front bound to 9 I'll also increase the rebound to 9)\

did you leave the anti-roll bars unchanged?
usually I increase the rear anti-roll bar to 6-7

toe & camber?
front toe 2.5-3.5, rear toe stock

ride height, is it level or not?
slammed for drift cars, 90-100mm for race cars

as you are drifting what about LSD set-up?
I don't know how to adjust LSD. so I usually leave it stock (full customized, stock settings)

I know all these factors will affect the car, but you can't say that if I increase the camber or two and now suddenly lower spring rate in front will create more oversteer. Lower spring rate in front will still create more understeer, just maybe to a lesser degree with more camber or toe. I know there's two sides to this agrument, but I just find that the OP's finding is consistent with my own experience. I guess you just have to test it out and see what to believe.

 

[Scaff]

by how much?
usually 30-50% higher than stock

did the rear change at all?
usually 10-20% lower than stock

what about the differences between bound and rebound?
usually I keep the bound a rebound the same. (ie if I increase the front bound to 9 I'll also increase the rebound to 9)\

did you leave the anti-roll bars unchanged?
usually I increase the rear anti-roll bar to 6-7

toe & camber?
front toe 2.5-3.5, rear toe stock

ride height, is it level or not?
slammed for drift cars, 90-100mm for race cars

as you are drifting what about LSD set-up?
I don't know how to adjust LSD. so I usually leave it stock (full customized, stock settings)

I know all these factors will affect the car, but you can't say that if I increase the camber or two and now suddenly lower spring rate in front will create more oversteer. Lower spring rate in front will still create more understeer, just maybe to a lesser degree with more camber or toe. I know there's two sides to this agrument, but I just find that the OP's finding is consistent with my own experience. I guess you just have to test it out and see what to believe.

I will have to give these a try, setting one at a time and looking at each result.

However the info you have given above does raise some interesting observations. I'm only going to cover the points you have given enough info on.

Spring Rates - The percentage you lower the rear springs by is quite extreme for some default values, You could raise both the default spring rates by as much as 30% in a lot of cars just to get a good starting point. So softening the rear default to such an extent could certainly qualify as an extreme setting, take the Viper SRT-10, the default rear spring is around 5.5. lower that anymore and the rear roll ends up quite severe under track loads. The result is not an increase in cornering grip, but a reduction due to the level of roll and contact patch issues. I know GT4 does not model these exactly, but from the very extensive tests I've done it certainly does simulate the effect.

Camber (I asume as you use the right values as toe can only be increased by whole numbers), you increase this at the front but not the rear, which will give more cornering grip to the front end, reducing understeer.

Stabilisers/Anti-roll bars - You increase this at the rear but not the front, this can have a major effect on the grip at the rear. They are a very powerful tool in this regard and depending on the car the effect can be strong.

Dampers - Without knowing if you differ them front and rear its hard to say what the exact effect would be, but high values (you mention 9) have a very restricive effect on soft springs (less on hard springs) by reducing the springs ability to act, effectively increasing the spring rate.

GT4 itself - One of the issues I have with GT4 is that the range on the spring rates is too low, generally the lower values are lower than you would want to go on the track, but the higher values stop far short of the values used in most motorsport. GT4 never really allows us to play with seriously firm spring rates in GT4. Hard springs in GT4 and hard racing springs in the real world are very different indeed.

Regards

Scaff

 

[KSaiyu]

But from my own experience, in most cars and in most circumstances, increasing the front spring rate and damper rate will increase the front grip and induce more oversteer.

Remember that this is not a simple sliding scale - most cars in GT4 are front engined resulting in a large mass above the front axle. Stiffening the front a little may actually increase oversteer as it is keeping this mass in the front in "check", sharpening response. Yes, the stiffer end generally loses grip compared to the softer side, but there are variables which can lead to unexpected results.

 

[Scaff]

Remember that this is not a simple sliding scale - most cars in GT4 are front engined resulting in a large mass above the front axle. Stiffening the front a little may actually increase oversteer as it is keeping this mass in the front in "check", sharpening response. Yes, the stiffer end generally loses grip compared to the softer side, but there are variables which can lead to unexpected results.

Which is exactly why I set my spring rate and dampers for the car and track first, adjusting the front and rear values equally first. That give the 'standard' that I use to move from (only one value at a time, by small amounts and only one end at a time), adjusting now to balance the car.

My view is that you can't balance the car until its at least able to handle the loads that it will encounter around the track.

Regards

Scaff

 

[nos2]

I will have to give these a try, setting one at a time and looking at each result.

However the info you have given above does raise some interesting observations. I'm only going to cover the points you have given enough info on.

Spring Rates - The percentage you lower the rear springs by is quite extreme for some default values, You could raise both the default spring rates by as much as 30% in a lot of cars just to get a good starting point. So softening the rear default to such an extent could certainly qualify as an extreme setting, take the Viper SRT-10, the default rear spring is around 5.5. lower that anymore and the rear roll ends up quite severe under track loads. The result is not an increase in cornering grip, but a reduction due to the level of roll and contact patch issues. I know GT4 does not model these exactly, but from the very extensive tests I've done it certainly does simulate the effect.

Camber (I asume as you use the right values as toe can only be increased by whole numbers), you increase this at the front but not the rear, which will give more cornering grip to the front end, reducing understeer.

Stabilisers/Anti-roll bars - You increase this at the rear but not the front, this can have a major effect on the grip at the rear. They are a very powerful tool in this regard and depending on the car the effect can be strong.

Dampers - Without knowing if you differ them front and rear its hard to say what the exact effect would be, but high values (you mention 9) have a very restricive effect on soft springs (less on hard springs) by reducing the springs ability to act, effectively increasing the spring rate.

GT4 itself - One of the issues I have with GT4 is that the range on the spring rates is too low, generally the lower values are lower than you would want to go on the track, but the higher values stop far short of the values used in most motorsport. GT4 never really allows us to play with seriously firm spring rates in GT4. Hard springs in GT4 and hard racing springs in the real world are very different indeed.

Regards

Scaff

Yes, I meant camber 2.5-3.5 in my previous post, sorry about that. And I usually have +1 toe in the rear if it's necessary. As for the dampers I usually run the same bound and rebound value but different front to rear. (for example 8 bound and rebound for front, and 6 bound and rebound for rear).