How to tune up your suspension

[NoTurbo]

As some of you will already know, I am a bit obsessive about suspension. Having tested 4 different setups on my car before finding what I liked I found this article and it all made sense.

In short stiff shocks, matched with softer springs and bushes.

"If there’s any message I’d like to get out there, it’s that the best suspension is not the one with the most spring rate, but the one with the best shock damping that’s designed to work with the chassis and has as little spring rate as you can put in that gives you the best handling,”a he says. ”aThat’s the optimum setup for any race car, even an F1 car.”a -T.C. Klien

Full write up here: http://www.bimmer-mag.com/issues/101/ar ... 2nZ-XNwbqA

[Demlotcrew]

A lot of generalisation in that advitorial. I would like to see some data to back up their statements before making any sort of conclusion.

I actually think a stiff shock causes all sorts of handling issues, not a formula I would have expected to work........

[harry_p]

You usually have to use the softest spring you can get away with for body control and resist roll, and then tune the dampers to match, and finally add arbs to fine tune the balance.

Not so easy on a road car where you need bump compliance and some sort of ride quality, so you end up using softer springs and thicker arbs to effectively increase cornering spring rate without having much effect on ride quality.

Softest spring you can get away with does NOT mean soft springs! I don't know what sort of spring rates dtm e30s ran, but I would imagine them being several times higher than you'd ever dream of using on a road or occasional trackday e30.

In my experience it's easier to spoil a cars handling by over damping it, which leads to an uncomfortable and wooden feeling car. A lot of manufacturers tend to over damp cars for a 'sporty' feel, and even though it sounds the wrong way round, you can often improve both comfort and handling by fitting stiffer springs which are a better match to the dampers.

[capnmchl]

It depends what you want from a car. Conventional suspension CANNOT provide both comfort and a sport ride, a compromise has to be made somewhere. It goes far beyond spring rates and damper settings as well.

[Demlotcrew]

It depends what you want from a car. Conventional suspension CANNOT provide both comfort and a sport ride, a compromise has to be made somewhere. It goes far beyond spring rates and damper settings as well.

Modern electronic dampers and progressive springs can go a long way to add comfort and at a flick of a switch 'sport' handling.

Also depends on the suspension, MacPherson, double wishbone etc.

[capnmchl]

It depends what you want from a car. Conventional suspension CANNOT provide both comfort and a sport ride, a compromise has to be made somewhere. It goes far beyond spring rates and damper settings as well.

Modern electronic dampers and progressive springs can go a long way to add comfort and at a flick of a switch 'sport' handling.

Also depends on the suspension, MacPherson, double wishbone etc.

Hence the word conventional. They are still compromises though. Technically all those switches do is change the damping rates. The most famous is the Delphi MagneRide but there are others. With progressive springs, the change in suspension angle/geometry through the loading up of the soft spring rate still effects the handling. You may be able to negate it in some double wishbone setups though.

The only true way to have both is a fully active suspension system but very few companies have mastered the concept, let alone installed it succesfully. The only three companies that come to mind are Toyota and Nissan in the early nineties and Bose, who are still playing around with that Lexus Ls400 on electromagnetic suspension. I'm not well versed enough with Citroen Hydractive 3 to comment on that though. I'm pretty sure it's the same as Hydractive 2, with a bit more computing power.

Other things such as ARB's, unsprung masses, weight distribution, suspension design, spring design (torsion bar, coil spring) go a long way to determine how the vehicle handles.

[Demlotcrew]

What about the McLaren 12C with its linked damper system and Z control bars? I think they have pretty much mastered it........

[capnmchl]

All of these catchphrases banded around by marketing people are not as technologically impressive as you think, and non of it's particularly new. The whole system does let them use softer springs, which is a bonus in terms of passenger comfort, road handling and comfort. It's not quite a full active suspension system because it still has springs.

The linked anti roll bars are nothing more really than a rework of the 50 year old BL Hydrolastic system. Rather than make them run longitudinally though, McLaren have made them run transversely, linking the rebound from one shock absorber to the compression on the other. There is an element of electronic control, and that's where the vehicle loses all it's roll from. It's essentially an infinately adjustible ARB that's controlled by an ECU rather than the driver. So it is a smart solution, but it still uses traditional coil springs and shock absorbers.

The Z link is simply a solution to stop the rear of the car compressing under high aerodynamic loads, rather than having to use rediculously high spring rates, which would ruin the car.

Don't get me wrong, I'm sure a McLaren 12c is a beautiful car to drive, and my minimal talent at driving would make the most of it, and the same goes for many cars, but it is still a compromise.

[Demlotcrew]

Its far more impressive than any other manufacture has installed on their cars FACT, its certainly an example that escaped your list and one that doesn't need to compromise despite what you might think after researching the net.

[NoTurbo]

I like the Spyker layout http://bit.ly/Qem3Sw

What is this set up called?

[Demlotcrew]

Thats pushrod.

[capnmchl]

Its far more impressive than any other manufacture has installed on their cars FACT, its certainly an example that escaped your list and one that doesn't need to compromise despite what you might think after researching the net.

It's really not. Boiled down, it's still a reactive suspension system, with set spring rates and damper rates that has an element of electronic control to stop the car rolling. It will be compromised at some point. Granted that point may be rare but it is not as advanced as a fully active system.

Mercedes active body control is probably the most advanced system avaliable at the moment, and that's just a relabelling of Citroens Hydropneumatic and Hydractive systems.

[Demlotcrew]

The Mercedes active body control system is far less sophisticated than whats on the 12c, its very hard to compare the two. I also feel I must point out the dampers on the 12c are not set, they are fully electronically adjustable on compression and rebound.

For others reading this, the 12c does not have any anti roll bars, its all hydraulic with a cross over valved design.

[capnmchl]

The Mercedes active body control system is far less sophisticated than whats on the 12c, its very hard to compare the two. I also feel I must point out the dampers on the 12c are not set, they are fully electronically adjustable on compression and rebound.

For others reading this, the 12c does not have any anti roll bars, its all hydraulic with a cross over valved design.

Fair enough. I would personally say that it's more of an acheivement making a big comfy saloon go around corners like a sports car than making a sports car comfortable for everyday use. I do sort of agree with it not being that sophisticated - as I said, it's basically a rehash of Citroens Hydropneumatic and Hydractive systems, neither of which are truely fully independantly active and are still fundamentally based on a 70 year old design. Neither is the 12c though - the method of linking the dampers together is much like Hydrolastic, albeit far more sophisticated in every way. But it does mean that whatever one does, the other has to react to it. The level of electronic control is what makes it good at what it does.

Vis-a-vis, my point about set dampers does not come across great. I appreacte the electronic control can adjust them, as can the flow of fluid between the dampers, but a damper is still a set object - it's valving has limitations and the construction also lends itself to limitations, be they negligible or not.

I will concede that the 12c probably is an amazing car to drive, regardless of where it's driven, and as I said, my personal driving skill (which is minimal in the grand scheme of things) will be far outmatchded by its electronics. However, I don't belive it's the best suspension ever implemented into a road car. In reference to my list, the Toyota was a Lexus Soarer of the early 90's, which, AFAIK is and was the only production car to come with a fully independent active suspension system.

PS - I don't normally like arguing about stuff on the internet, but suspension is more fun than writing my dissertation on the effects of cold starting engines

[pony]

New Genuine BMW M Technic springs
New Bilstein B6 Sport shock absorbers are what I have

Also
Rear
Rear beam bushes; Rear trailing arm bushes, Rear anti-roll bar bush, Rear diff bushes New Powerflex (for drifting)
Front bushes E30 M3 eccentric front wishbone bushes

[Demlotcrew]

The Mercedes active body control system is far less sophisticated than whats on the 12c, its very hard to compare the two. I also feel I must point out the dampers on the 12c are not set, they are fully electronically adjustable on compression and rebound.

For others reading this, the 12c does not have any anti roll bars, its all hydraulic with a cross over valved design.

Fair enough. I would personally say that it's more of an acheivement making a big comfy saloon go around corners like a sports car than making a sports car comfortable for everyday use. I do sort of agree with it not being that sophisticated - as I said, it's basically a rehash of Citroens Hydropneumatic and Hydractive systems, neither of which are truely fully independantly active and are still fundamentally based on a 70 year old design. Neither is the 12c though - the method of linking the dampers together is much like Hydrolastic, albeit far more sophisticated in every way. But it does mean that whatever one does, the other has to react to it. The level of electronic control is what makes it good at what it does.

Vis-a-vis, my point about set dampers does not come across great. I appreacte the electronic control can adjust them, as can the flow of fluid between the dampers, but a damper is still a set object - it's valving has limitations and the construction also lends itself to limitations, be they negligible or not.

I will concede that the 12c probably is an amazing car to drive, regardless of where it's driven, and as I said, my personal driving skill (which is minimal in the grand scheme of things) will be far outmatchded by its electronics. However, I don't belive it's the best suspension ever implemented into a road car. In reference to my list, the Toyota was a Lexus Soarer of the early 90's, which, AFAIK is and was the only production car to come with a fully independent active suspension system.

PS - I don't normally like arguing about stuff on the internet, but suspension is more fun than writing my dissertation on the effects of cold starting engines

No arguments here, just facts

I dont think the Mercedes can quite corner like a sports car, but I get the metaphor.

[NoTurbo]

Do you guys think that we will ever get an adaptive suspension system that does not need it's own ecu?

It would be interesting to see. One possible way it could be done would be through clever valving and hydraulic compensation. I quite like the idea of reducing roll and bounce progressively using hydraulics

Anyway the point of the article was that stiffer springs are not always the best way to tune up your handling. No one really mentions the pull effect on shock absorbers. It is always a conversation about stiffness and bounce reduction. not in corner control due to reduction in roll(from shocks and springs not arb), torsen of the chassis and bushes matching springs etc.