front spring effect discussion (with testing results)

[nomis3613]

Hi, I was curious about why stiff front springs are popular on FFs, so here's a couple of tests I did:

(testing conducted offline at London with sixaxis controller)

f spring | laptime | comment
Mk1 GTI- sports soft
10 . . . . . 61.9 . . . . . sloppy initialy steering reaction
15 . . . . . 61.0 . . . . . sharper turn-in, same mid-corner balance but less transient u/s

Mk1 GTI- racing soft
10 . . . . . 58.3 . . . . . same braking as sports soft, main difference is traction
15 . . . . . 57.9 . . . . . sharper turn-in, same mid-corner balance but less transient u/s

Nissan 370Z- sports medium @ front, sports soft @ rear
11 . . . . . 57.5
17 . . . . . 57.5 . . . . . slightly sharper turn-in, possibly a touch more low speed u/s

Nissan 370Z- racing soft, weight balance 50/50
11 . . . . . 54.6 . . . . . low steering, twitchy rear
17 . . . . . 54.4 . . . . . slightly sharper turn-in

Nissan 370Z- racing soft weight 55/45
11 . . . . . 54.3 . . . . . gently u/s, much easier to drive than 50/50
17 . . . . . 54.4 . . . . . no difference

(to explain the strange testing configuration for the 370Z: with sports softs, the car was far too loose for consistent testing. To avoid extreme suspension settings, I chose to put sports mediums on the front instead. Even so, the baseline setup was still more loose than I'd like when testing settings. After I finished the racing soft 50/50 testing, I noticed that the 370Z had a heap of rear ballast. D'oh! So I repeated the racing soft test, this time using a touch of front ballast to achieve 55/45, which turned out to be a much better baseline for testing)

My thoughts:
1) Definitely doesn't follow textbook theory (or in-game help text) of stiffer front = more understeer. The bumpy course muddied the waters a bit, but on smooth, sweeping corners, the stiff front springs had the same front grip as the soft springs.

2) For the Golf, the increased speed seemed to come from less "steering lag". I'd be interested to hear how this goes for drivers using a wheel (perhaps the smoother inputs used would reduce the difference?)

3) The 370Z felt better with stiff front springs, but it didn't translate into lap times. Why?? Possibly because the handling wasn't as nose-heavy as the Golf, so the laptimes are not purely down to front grip. Although the 55/45 weight dist result is puzzling, I'd expected the stiffer front to result in a big improvement given that the handling was now more similar to the Golf (eg nose-heavy weight balance and gentle understeer).


I'm keen to hear what other tunes out there think.

Simon

EDIT: more testing in post 7 below: https://www.gtplanet.net/forum/showthread.php?p=7970959#post7970959

 

[Broseph]

but on smooth, sweeping corners, the stiff front springs had the same front grip as the soft springs.

That's because once you are in the turn the wheel is loaded, spring rate makes no difference. It only makes a difference on the initial turn-in during weight transfer.

You did not get the results you were expecting with the nose-loaded Z car because unlike with the Golf, those front wheels are only being used for turning, not for propulsion.

 

[Motor City Hami]

That's because once you are in the turn the wheel is loaded, spring rate makes no difference. It only makes a difference on the initial turn-in during weight transfer.

I'm not sure about that statement? Once a spring is loaded, where does the energy go? It didn't disappear just because the car loaded. That energy is still pushing down on the tires and affecting grip, mid corner.

Nomis - nice test. I am experiencing the same on some cars, but others just don't respond to this same method. More confusing physics programming from PD. Even between different FFs. The Civic EK really liked heavy front springs, but the Civic Type R '08 didn't. I am admittedly a little lost on spring rates in GT5.

 

[Broseph]

I mean once the spring has been fully loaded, it's spring rate becomes irrelevant, until the time you start unloading the spring. Basically, the spring rate at any given corner of a car only comes in to play at the moments that the ride height is changing (during compression and during extension)... Once you have entered in to your turn and the spring and shock have fully compressed, the energy is stored in the spring and the spring rate has no effect on anything until you come out of the turn and the spring & shock go into extension, releasing the energy.

 

[nomis3613]

I am experiencing the same on some cars, but others just don't respond to this same method. More confusing physics programming from PD. Even between different FFs. The Civic EK really liked heavy front springs, but the Civic Type R '08 didn't. I am admittedly a little lost on spring rates in GT5.

Yeah, it's very confusing, especially when cars which should be very similar react very differently.

I mean once the spring has been fully loaded, it's spring rate becomes irrelevant, until the time you start unloading the spring.

Thanks for the explanation.

But the textbook theories say that spring rates affect balance, even mid-corner. For example if the front is stiffer, the front will have more weight transfer (ie the outside tyre will carry a lot more weight than the inside), which reduces front grip. But not in GT5 apparently...

Cheers,
Simon

 

[Johnnypenso]

That's because once you are in the turn the wheel is loaded, spring rate makes no difference. It only makes a difference on the initial turn-in during weight transfer.

You did not get the results you were expecting with the nose-loaded Z car because unlike with the Golf, those front wheels are only being used for turning, not for propulsion.

Unfortunately there are no real springs in GT5, only bits and bytes and calculations to mimic PD's idea of what a spring might do. If things worked in GT5 the way they did in real life, tuning would be much simpler

 

[nomis3613]

Thanks to Motor City Hami for loan of the Civics, I now have more results to add to the pile. Both Type R's are 60/40 weight balance and running sports soft tyres. Camber for the EK was 2.8/0, for the '08 was 2.7/0.5.

f spring | laptime | comment
EK Civic
6 . . . . . 60.7 . . . . . moderate understeer in general, poor turn-in
12. . . . .60.0 . . . . . sharper turn-in, perhaps slightly less understeer

'08 Civic Type R
7 . . . . . 59.8 . . . . . well balanced
14. . . . .59.7 . . . . . slightly sharper turn-in, slightly more unsettled on bumps

Again, we're definitely not seeing any "stiffer front = more understeer". The main difference I think is that the stiffer springs improve the initial steering response. As for why the EK liked the stiff front springs but the '08 didn't, my theory is
- the EK needs every scrap of front grip it can get, therefore the extra grip at turn-in improved the laptime
- the '08 is already well balanced, so there is less advantage in a bit more front grip. Therefore the loss of grip over bumps (surprisingly, the '08 Civic is the first car in this testing that has handled bumps/kerbs worse with stiffer front springs) cancelled out any improvement due to turn-in.
Well, that's just my attempt to make some sense out of all of this!

 

[CyKosis1973]

Unfortunately there are no real springs in GT5, only bits and bytes and calculations to mimic PD's idea of what a spring might do. If things worked in GT5 the way they did in real life, tuning would be much simpler

Word...

As for why the EK liked the stiff front springs but the '08 didn't, my theory is
- the EK needs every scrap of front grip it can get, therefore the extra grip at turn-in improved the laptime
- the '08 is already well balanced, so there is less advantage in a bit more front grip. Therefore the loss of grip over bumps (surprisingly, the '08 Civic is the first car in this testing that has handled bumps/kerbs worse with stiffer front springs) cancelled out any improvement due to turn-in.
Well, that's just my attempt to make some sense out of all of this!

Wheelbase may be a factor in the differences between these two cars. Try finding cars that are closer in length. It maybe that the longer wheelbase of the '08 helps to moderate weight shifting by making the period longer and slower than a shorter vehicle ... maybe ...

{Cy}

 

[Motor City Hami]

Weight could have something to do with it too?

Type R (EK) '97 at 1050kg
Type R '08 at 1270kg

 

[CSLACR]

As long as you use different cars, the results will be slightly, well, different.

If anyone's been looking at my tunes lately, they'd see that since 2.09 I've stopped using ride height/springs for rotation, because it doesn't seem to work anymore, and I now use them solely for other reasons.

Cars that turn in too much, end up like this

Suspension:
10/-10
12.0/15.5
6/4
5/7
3/3

Camber/Toe:
2.0/2.0
+0.05/+0.10

BB: 5/2
ABS: 1

Bold affects turn-in. Long story short I agree.
FTW this car turned in way too much, anything bolded was used to stop it from rotating so damn much entering corners.


I haven't tuned a FWD since 2.09, but given the general tendency to understeer on entry in GT5, most will likely be more like this:

Suspension:
-10/10
15.5/12.0
4/6
7/5
3/3

Camber/Toe:
2.0/1.0
-0.15/-0.10

BB: 5/2
ABS: 1

Obviously rear toe would be dropped for overall rotation on any FWD I've driven, probably negative.