Weird GT 86 factory spring rates in GT5?

[fatoni]

Originally Posted by Dimman

6kg/mm is ~335 lbs/in and that doesn't sound like a huge number. 111 lbs/in on the rears sounds soft.

dont read too much into that. it has more to do with motion ratios than that. my ae86 had 6/4 kg// but it had a much rougher ride than my miata with 550/350 lbs/ft. 6kg/mm in what im assuming the front suspension is going to be like in the frs is going to be out of control

[old greg]

Originally Posted by Dimman

6kg/mm is ~335 lbs/in and that doesn't sound like a huge number. 111 lbs/in on the rears sounds soft.

Everything is relative. With a front motion ratio of ~1:1, 6 kg/mm is way too stiff for this car.

[fatoni]

Originally Posted by lfawishes

maybe this is why it drifts so much



What are the lbs for my RCE Blacks? I installed and x-brace and seem to be spining the rear tires on bumpy canyons during which there is no front end loss of grip just zips to redline with a tire spin real fast. Should I back down my ohlins?

thats the exact opposite of what you are thinking. and you arent getting the concept. we are talking about spring rate not inadequate damping

[Dimman]

Originally Posted by old greg

Everything is relative. With a front motion ratio of ~1:1, 6 kg/mm is way too stiff for this car.

Just a knee-jerk reaction to the numbers because of past Supra ownership. Supra being ~600lbs heavier plus having double-wishbone front suspension. Maddeningly, also different motion ratios on the front and rear so it also had a large front:rear coil rate difference.

[Racecomp Engineering]

Originally Posted by Homemade WRX

Glad to see that you and Myles are on board. I know of two local customers (old nasioc guys) who will be picking up cars, one an FRS and the other a BRZ. Both are going to have planned down time for some component development. Perhaps we can work on getting some components to you for measurement and then you'll have to chassis' for guinea pig testing too.

-Micah

P.S. the guys are in Falls Church and Hagerstown and the cars will be on the lift in Hag...

Awesome...pm me your email. And we should have met up at PRI!

- Drew

[Racecomp Engineering]

Originally Posted by lfawishes

I was asking RCE about the rates of the springs I have that they make because I forget what they are. Was asking about backing down the ohlins because I thought they might know, I seemed to be getting some tire hop and spinning the rear tires so it reved up real fast over bumps when driving fast on canyon roads. Just installed the rear x-brace and running 11 or 12 all around on for dampening


Anyways I get your point about the fr-s, i was being off topic

285 lbs/in front 265 rear for GD impreza. 15mm drop front and 10 rear. Yes, try slightly reducing the rear damping.

So in comparison, the much much lighter front end of the ft86 has a lot more spring from the factory than our performance springs for STi...sounds fishy to me. 6kg/mm (336 lbs/in) is pretty high.

We'll have to see.

- drew

[Ryephile]

For what it's worth, I think this is where the "simulation" aspect of GT5 really fails. If you go and adjust the spring rates [i.e. rear springs to 15kg/mm], the steady state handling balance doesn't shift grip from the rear end like it should; if anything it makes the car understeer even more, which means their physics are not built on reality but something abstract.

We'll have to see what the actual car spring rates and wheel frequencies are before we go making real-world tuning decisions.

[Spaceywilly]

from the MotoIQ suspension article

The strut is mounted pretty far inboard so the suspension motion ratio is going to be pretty high for a strut which means a relatively stiff spring will be needed. This part of the suspension geometry is pretty reminiscent of the Nissan S chassis which we consider to be a very good execution of a MacPherson strut.

http://www.motoiq.com/magazine_artic...cion-fr-s.aspx

[old greg]

Originally Posted by Spaceywilly

from the MotoIQ suspension article

From the MotoIQ suspension article thread.

Originally Posted by Ryephile

they're mistaken on the strut having a motion ratio other than 1:1 [disregarding inclination angle or virtually inapplicable absurd force vectors from asinine wheel offsets].

[Spaceywilly]

yep you're right, looking at the photo it looks like the strut is directly attached to the knuckle (guess it couldn't really be any other way in a macpherson setup) so it has to be 1:1 or very close to it.

[fatoni]

Originally Posted by Ryephile

For what it's worth, I think this is where the "simulation" aspect of GT5 really fails. If you go and adjust the spring rates [i.e. rear springs to 15kg/mm], the steady state handling balance doesn't shift grip from the rear end like it should; if anything it makes the car understeer even more, which means their physics are not built on reality but something abstract.

We'll have to see what the actual car spring rates and wheel frequencies are before we go making real-world tuning decisions.

well in moderation i have noticed that it does. maybe the extremes of the model dont work but its good enough for the intents. of course its not perfect but its a 60 dollar game. kinda like how newtonian physics isnt correct by any stretch but it was close enough to get us to the moon in one piece.

[Kostamojen]

Drove it in GT5 last night...

If it drives ANYTHING like it does in the game, its gonna be epic.

Although it didn't sound anything like it does in the videos we've seen

[Dimman]

A quick cut & paste from something I was working on last night:


I’m going to have to question some of what’s been suggested here. Maybe double check some math or something. I’ve been going over more of my books and came up with this:

Using the following:
2680 lbs
170 lbs driver
53/47 split
75 lbs/side front un-sprung (150lbs total)
70 lbs/side rear un-sprung (140lbs total)
14” lower arm for the front suspension (not really important since a MacStrut is 1:1)
14” lower arm for the rear suspension with coil-over mounted 8” from chassis-side pivot
330 lbs front springs, 290 lbs fitted
110 lbs rear springs, 100 lbs fitted

Results for frequencies were 86.7 cycles/min front (1.44 Hz) and 94.9 cycles/min rear (1.58 Hz).

These results

A) put the front frequency at ~91% of the rear, this fits with the road car trend to reduce pitch oscillation.

And

B) put both the frequencies right in the middle of the range that is considered to be slightly firm/sporty.

Now I’ve made some significant assumptions on stuff like un-sprung weight, spring mounting angle (rears being more vertical), arm lengths and where the shock mounts to the rear arm (but based on the current Impreza’s looking to be somewhat close to the middle of the arm and it‘s just for a ratio so…).

But as it stands from my guesstimations, using the formulas from one of my suspension books, the 6kg/mm front and 2kg/mm rear spring rates look legit. Also it’s probably not an accident on GT5’s side either as the FT86C has the same rates, and the ‘tuned’ G Sports concept has 9/5 (which with my numbers would work out to ~1.8Hz front and ~2.5Hz rear, not perfect but… more dorifuto friendly??? Compensating for the giant tuner wing’s downforce at speed???)

Also I have not been able to find any confirmation of motion ratios needing to be accounted for in a situation where the damper and spring are mounted in-line (coil-over).

So, thoughts? If you guys think I’m way off, let me know. Maybe I’m the one with the bad math, and it’s coincidence that the results look like they work…

Final thought is, without knowing the exact leverage of the rear it’s going to be very hard to guess close because of the nature of squaring that number for frequency calculations, which turns little mistakes into big ones…


Also, Ryephile I disagree with how you say that jacking the rear spring rates in GT5 cause understeer, but that's for the Forza vs GT thread (thread? knife-fight? heh...)

[Ryephile]

Originally Posted by Dimman

Also, Ryephile I disagree with how you say that jacking the rear spring rates in GT5 cause understeer, but that's for the Forza vs GT thread (thread? knife-fight? heh...)

I'll admit I was being dramatic, however for making the spring rate 3X, it makes a marginal change in steady state cornering balance. That right there tells me GT5's physics engine is flawed. Then again, I've struggled to make logical [reality/experience-based] correlations in suspension setup [with other cars I'm very familiar with] in GT5 since its release. GT5 is still not quite a simulator.