sound_wave

Hello folks,

Ok so I'm bored in work so started reading about suspension setups and grip. Reading further has ended up with me getting somewhat confused.

Now, I've always thought that when you are on track, you want your dampers set to full hard, but when reading this, it seems that softer settings lead to more grip.

Having front dampers softer than rears gives more grip at the front, making a car understeer and vice versa, so I'd have thought that you want softer settings on track, to make the car grip better?

Also, how do different spring weights help? On here, most with coilovers seem to run 10/10kg. I'm running. 8/6kg - does that mean mine will grip better, as they are softer?

I've always had my dampers set harder at the front than at the rear, however, reading in to it, I should have themsey softer at the front, to promote more grip?! Does this mean the car will turn in better??

(Yeah, like I said, I'm bored in work)

loftust

It's all about keeping the tyre in contact with the road as much as possible.

A stiff setup is good on a very smooth track, but that doesn't mean full hard is the right setup for that circuit. Over bumps, even small ones, you need the suspension to compress a certain amount to keep the car flat, and rebound in such a way that the tyre maintains contact with the road. Too soft, and the car will be bouncing around too much, and won't settle down at all...it will never reach a steady state.

Think about it another way - imagine a gun on the front of a warship, and it is parked facing the bow (000). Imagine there is another ship on the Starboard beam (090) (on the right, at a right angle) and it is moving towards your ship fast...you need to move that gun to face the enemy and fire. You need it to move fast, but not so fast that it overshoots 090, and eventually stops at 115. The computer in the gun realises 'oh crap, I need to move back to 090 quickly'. My point is that like your suspension, it needs to move fast, but not so fast that it goes beyond where it is supposed to. Stiffness of the spring, and the amount of suspension damping can be thought of in the same sort of way.

Weight transfer, thanks to a softer setup can help too; on turn in for instance, as it places more weight over the front wheels, which do most of the braking. A stiffer setup would prevent too much forward surge...it's all a balancing act.

This is only a snippet of info, a comprehensive reply would take a looonnnggg time. Things like squatting under acceleration needs to be considered for serious applications, and is one reason why you wouldn't want to be too soft at the rear.

I'd recommend reading more to understand the difference between grip, handling, compression, rebound, damping etc...think about how a wheel/tyre must move, in harmony with the suspension, to maintain contact. Not one statement about a suspension setup is true unless all the variables have been considered. Everything is a compromise too. You won't get maximum grip and maximum handling all at once. An understanding of control theory will go a LONG way too, so long as you can translate the knowledge.

Sent from my GT-I9300 using Tapatalk

lovegroova

Here's my limited understanding/random ramblings on the subject:

The more rubber on the road, the more grip you have.

Settings are relative front to rear, not absolute – the tyres will only offer up so much grip, it’s not unlimited. I did some experiments with various rear settings on a track with my old Gaz Coilovers

Here's a brief summary (the coilovers have 40 clicks, andall numbers are clicks from full soft):

1) Coilovers set at 16R 20F (day to day settings) and tyrepressures at 32PSI cold. Pressures rose to 40PSI. Car drove pretty much as it normally does on the circuit, nice stable front end, a bit understeery at times.

2) Coilovers set to 24R 20F, pressures reduced to 31PSI,Tyre temp consistent across the width of the tyre, around 47C - Car drove like an S2000, grip, grip grip, then a quite sudden breakaway.

3) Coilovers set to 20R 20F, pressures reduced to 31PSI (had risen to 33 again), consistent tyre temp again - Rear end very communicative, a gentle squeal from the tyre and a nice slow slide - lots of fun but perhaps a tiny bit wallowy

4) Coilovers set to 22R 20F, pressures 31PSI, A nice middle ground, enough communication that sliding is about to happen, but easy to balance the car, and also to do a bit of messing about (as Ninebolts will testify), and easy to manage when I got it a bit wrong. Care needed for the first few corners until the tyres get warmer and the pressures rise to working temps.


Tracks are smooth, so the suspension doesn't have to workhard to keep the tyres in contact with the road surface as it might do on a bumpy road, so you can get away with stiffer settings to reduce body roll(which will make you slower in corners) and dive under braking/squat under acceleration

The relationship between springs and dampers is very important, it's not just about spring settings, which many people seem to get fixated upon - the dampers have a far larger effect. I know MB has gone with softer springs for this season's racing. Perhaps a softer spring and stiffer damping.

You also have to take into account both the compression and rebound elements of your dampers - this is a black art!

Dembo

10/10 for using the right word ;-).

You're grossly over simplifying all of this by referring to grip. What does grip mean? And more importantly, when? If it was as simple as "X gives you more grip" then F1 teams wouldn't need to spend all day setting their cars up.

Remember that less roll at one end (i.e. stiffer) means less grip - i.e. stiffer front ARB = understeer, but that's mid corner where the dampers aren't doing anything. The dampers affect the transition. So when you're turning into the corner if your front dampers are stiffer the front will take longer to roll than the rear which will mean you tend to understeer on the way in. On the way out of the corner, the opposite is happening, as the car returns to level, so the front takes longer to react and you now get oversteer.

I'd find mine was better with the front set one click (out of 9) softer than the (full hard) rear. That would mean entry oversteer (i.e. better turn in), but exit understeer - which might sound bad but in RWD that means more traction. If you set the front stiffer, as above, then you're going to get the worst of both worlds.

So that's part of it. Of course what happens with bumps is an entirely different subject, plus there's dive and squat, and suspension geometry changes to consider.

I make no claims of understanding it all.

chrispayze

VERY simply, with all else being equal, and within reasonable bounds, softer suspension yields more grip due to the grater weight transfer (ie lots of weight on the outside tyres pushing the tyre into the ground). However, the speed of response is very poor because the mass of the car body has to move so far from one side to the other between corners (assuming the same contribution to roll stiffness from the ARBs in each case). This roll also changes the angle of the tyres on the track, so greater (static) camber is required to make the tyre sit flat when under load. This means there is less tyre in contact in a straight line, requiring a slower transition to allow the contact patch to gradually increase (along with the grip). Quickly loading the tyre in this situation will overload the available grip before the weight transfer and suspension movement has occurred.

All this shows the need for a stiffer setup, to improve the response of the car, enabling the grip to build more quickly (due to less suspension movement, quicker weight transfer).

BUT, this comes at a cost of outright grip. Hence the need to balance grip with response, plus add in the pitching (front to back weight transfer and movement) and the bumpiness of the track and it all gets a bit more complicated! Plus the damping, affecting the speed of the suspension movement in various situations (high speed bumps versus slow weight transfer) and it gets even more complicated!

That's my understanding. Happy to be told I'm wrong!

noodels

Maybe tomorrow have a look at linky if still bored

http://www.blackartdynamics.com/

chrispayze

Cheers for that link, looks interesting.

BuggyofMildDiscomfort

You get more grip the softer the suspension is, because it reduces peak loads on the tyre carcasses.
However, it also allows more body roll, which means the suspension geometery may not control the tyre footprint well enough (i.e, not keeping the tyre square to the road), which then compromises grip.
It also means it takes longer for the car to respond and settle down, which often means a driver can't get the most out of a car set soft enough for optimum grip, because there's little leeway for hustling the car where you want it, and you need a lot of anticipation and a smooth driving style to extract the performance. 99% of the time you have to go stiffer to give the driver the confidence and leeway to move the car around a little to make up for mistakes, etc, unless they sign their name with Hamilton or Alonso at the end.

Damping needs to be matched to chassis stiffness, weights, and spring rates, just winding the dampers up to full hard for circuits hurts both outright grip and ride, and handling too if you go too far, because you'll overload the carcasses with every steering/control input, and make the car fight you all the way around the track.

chrispayze

Ah, I wasn't too far off then!

sound_wave

It really is a dark art, this suspension setup lark isn't it?
So if you set the rear dampers slightly harder than the front, how does having different weight springs affect this?
Would the effect of damping stiffness of 50%Fr -60%Rr be cancelled out by having softer springs in the rear?