How does suspension stiffness translates into high speed stability?

How does suspension stiffness translates into high speed stability?

Harder suspension allows for quicker weight transfer movement in a car, wether or not that also means more weight transfer is debatable, however for a track car its always better to have a stiffer suspension until you start to lose grip.

But how does this works on a high speed straight line car?

What suspension would offer the least floatiness and the most grip regardless of tire/wheelbase/aero downforce for, say, a wangan moster?

Depends on the quality of the road surface desu

Either you are telling me "suspension stiffness doesn't matter" or you haven't read what i typed.

What I'm saying is if you're going in a straight line on a shitty road surface with super hard suspension you're crashing.

On the other hand if the road surface is smooth you want stiff, low suspension and perhaps a little toe in on the front.

>however for a track car its always better to have a stiffer suspension until you start to lose grip.

Not true, you want as soft as you can get while maintaining ride height.

Take these extremes:

extreme bumpy road
soft = your car eats bumps easy, and will go smooth
stiff = your car will try to remain stiff and bounce

extreme flat road
soft = your car balance will shift to front/back/left/right in corners and up- downhills
stiff = your car will remain in balance at all times because of hardness

soft front, stiff back = reduce understeer
stiff front, soft back = reduce oversteer

Former professional setup guy here. (Worked at a full-service shop that built, tuned, and serviced road race and time trial cars.)

It's not quite as simple as this, and stiffness can be a real balancing act.

For example, if you go too soft with a bumpy road, you make the car susceptible to oscillations - in other words, one corner hitting a bump will compress the other corner, resulting in the whole car rocking back and forth, which makes the car much less stable than if it were on stiff suspension. You also need a reasonably stiff setup to control squat and dive.

Another complicated situation is the usual front/rear stiffness situation. The common logic is as you stated, but you need to be careful, for example a soft rear and stiff front can actually result in snap oversteer because "amplifies" rear weight transfer, causing a sort of pendulum effect. The reverse can apply and cause understeer, too.

The whole thing is kind of a mindfuck, to be honest, and the more time you spend around it the more you realize that 90+% of the people out there are actually making their cars worse by halfassing or cheaping out on their setups. Corner balancing and proper alignment are absolutely critical, adjustable suspensions without independent compression and rebound can often do more harm than good (which is why Konis+springs > cheap coilovers), and setup for any given car requires a lot of experience and quite a bit of trial and error.

Oh, also, my personal preference is to make any car just stiff enough that it maintains proper tire contact at all times, and then fine-tune the handling using alignment, tire pressures, and sway bars. It's arguably ever so slightly slower than an ultra-stiff setup, but it makes up for it by not beating the shit out of the driver, which lets them drive better and more than make up the difference.

No? a suspension way too soft increases the body roll which reduces the speed you can obtain while turning.

This is what i had already thought about suspension. You confirmed it, thanks.

I am talking on a flat surface. That's why i used a wangan monster as an example.

You have an ultra straight and flat highway, but the car wont fully be straight, you might need to make small correction, small degree corners, change lines, all the while doing 180mph+, and you want the least amount of floatiness and most amount of grip possible just changing the suspension stiffness (NOT counting the ride height since obviously lower is better)


Which one would be better in that case? a full stiff or a softer one?

Basically, Toe-In.

Don't want nervous steering at 180+ MPH.

Right. mild rear toe in and light front toe in. Forgot about that, however the stiffness of the damps and the shocks are still a doubt i wanna clear in my mind.

Why don't you stop being a sperg and go out there and try different set ups

>Inb4 its a tune for nfs

It shouldn't differ all that much from a road course setup. If the road is ultra-smooth, I'd go a bit stiffer than normal because you're carrying more momentum than usual into the turns.

Also, I noticed this bit in the OP:

>regardless of tire/wheelbase/aero downforce

But that's impossible. Tires and aero are huge factors in suspension setup, in fact the whole setup is basically tuned around them. A production-based car with a good splitter/wing/diffuser will run noticeably stiffer springs than the same car without aero and damping to match. The same goes for tires, especially when you start getting into the realm of R-comps and slicks.

Also, remember that springs are your primary setup tool. Shock adjustments are for fine-tuning.

>Inb4 its a tune for nfs

Oh yeah, if this is a video game tune, then just go fuck with shit. I've never encountered a video game that models suspension tuning properly, and shit sometimes even works backwards or whatever. I once built an exact replica of my shop's car (Stroked E92 M3 with full suspension including MCS 2-ways, aero, and almost 600lb lighter than stock WITH cage installed) in Forza and copied all of the settings, and it was an uncontrollable nightmare in game, I couldn't even get within 5 sec of real world lap times in it.

every simulator i try this for i cannot notice any actual difference, but i am sure that there HAS to be some.

>I've never encountered a video game that models suspension tuning properly
Not even rFactor 2 or BeamNG?

I know that many games would rather have cars made like hotwheel race cars and not emulate suspension properly, but there are a handful that actually do simulate suspension as something that keeps the car afloat the wheels.

Not sure about BeamNG but even rFactor doesn't get everything right.

I don't think it's currently possible to do a totally accurate simulation of suspension, for what it's worth. Even F1 teams have to do on-track testing to dial setups in, and there are also real-world factors that no game/sim accounts for, like how G-forces and feedback affect the feel of a car and the way it's set up. (For example a car might be fine IRL where you have constant feedback and can subconsciously adjust for it and drive the car in its "groove", but in the vacuum of a game it becomes a twitchy mess.)

I guess that's something that we can only wait for it to improve.

So to answer the main question: There is no correlation between high speed stability and stiffness. The grip at high speed depends of the same setting as the low speed , and the only way to improve grip on a high speed monster is through wheelbase, aero, or tires.

Is Gran Turismo as much of a meme as Forza?

Forza has a WAY better Tire model. (this could change in GT Sport, dunno)

As for Suspension modeling both are decent.

>this could change in GT Sport
>implying GTS will change anything

GT has been stuck ever since GT5. Fanboys just look at GTSports beta gameplay and get their panties wet while i look at it and notice no actual difference compared to the other games.

I want to see this fail to make polyphony realize that what they do with gran turismo its shit and that they need to change to keep up with the competition

Pls do not bully satania

no, turning speed is determined mainly by CG height to track width ratio, if you do not count effects from downforce, camber angle of the wheel to the road and tire size/compound.

It's physically impossible for the CG to be level with the road. To get the CG height as low as possible, the suspension would have no upwards travel at all (like a go cart with steel wheels). However, in a surface that's not perfectly smooth (i.e, all of them) that cause the wheel to jump away from the road, losing grip.

By allowing suspension travel (even if it's just the tire), you can allow the wheel to go down and follow the surface, not losing as much grip, so the turning speed can be higher.

So track engineers adjust a car by stiffening the suspension until it starts losing traction (or softening it until it stops gaining grip), and then lowering or raising it until it hits the bump stops in one or two places around the track. They will even compare different sections of the track to get a setup that works well say on 75% on the track and is slightly too soft or too stiff on the rest of it, simply because the time overall will be lower.

The answer to OP is both yes and no. You see whenever a car deviates from it's trajectory (a gust of wind, road inclination, a bump, etc.) the car itself will try to correct it because it's set to be naturally stable (understeer). However because the suspension can move, there is a lag between the disturbance and the correction. And at high speeds, a small disturbance will make the car go off the road if it's not corrected quickly. So a softer car will tend to wander at high speeds and feels less stable.

HOWEVER, suspension stiffness itself has actually very little to do with this effect (and none at all if you use very stiff anti-roll bars). The biggest part of it is actually due to tire, which is why low profile tires are thing; they have much higher lateral stiffness. Adding some toe in also adds stability.

another note: The lower the cg, the more bodyroll you can allow. Suppose you have two 2 meter wide cars, one with a CG height of 0,5 meters (sports car) and one with a CG height of 1 meter (suv). Assuming all tires are in the same condition in both cars, you can let the sports car roll a full 90 degrees keeping the same CG height and get better or equal lateral grip as the SUV even if it didn't roll at all. Which is why SUV's tend to have even stiffer suspensions than regular cars.

Of course, you could give the cornering grip of an sportscar to an SUV by making it lean inwards by force, like a motorcycle, but that requires a lot of power and wheel travel so it's impractical.