Adjustable Suspension: How to determine the right setting?

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Re: Adjustable Suspension: How to determine the right setting?

Quote:

Mr.Boss

Originally Posted by

Spring stiffness is not only material dependent. Few other parameters like coil dia, wire dia, pitch, etc affects the stiffness. Specific to this case, when the initial compression of spring is changed (pitch gets affected) it will alter the stiffness characteristics.

What is ride height?
Not in technical sense, but in layman's language, the ground clearance when car is in static position. At the springs side, there is some compression (static compression) due to the weight of the car.

dL = F / K

So, basically, this compression decides what the ride height could be, provided other lengths remain constant. What I am doing is changing this static compressed length by actually reducing free length, without changing number of coils in the spring. i.e reducing pitch.

But how max spring compression is reduced?
So now pitch is reduced. That means the coils are closer to each other (by dX, combined). Earlier the coils could be compressed by X distance after which the coils are hugging each other. But now, since the distance between coils is reduced by dX, the net compression is reduced to X-dX.

I hope I am able to replicate the picture I have in my mind.

Quote:

Mr.Boss

Originally Posted by

I couldn't imagine how to control / alter the spring initial compression at strut assembly level.

In our dampers, we can increase/decrease the fluid pressure in pistons to compress/expand spring.

Okay, now I see some relation to your figures. By shifting the spring seat we are able to change the ride height without changing the spring travel, and damping characteristics.

In our Formula Student car we can't think of changing the spring seat, for that we would have to change damper mounts (long process). What we do is vary our "Pushrod length" and pre load to achieve required performance.

We use Double Wishbone Independent suspension, unlike normal passenger cars which use McPhearson Strut.

Quote:

Mr.Boss

Originally Posted by

If you are looking for more details, kindly visit how do adjustable dampers work.

Sorry buddy, I couldn't understand which job are you referring to.

To Mod: Might consider shifting this thread to "Technical Stuff"Spring Rate depends on Coil Dia, Wire Dia and "No. of Coils" and not on pitch, all of which remains constant in this case. We are reducing the maximum spring travel to get increased ride height.Not in technical sense, but in layman's language, the ground clearance when car is in static position. At the springs side, there is some compression (static compression) due to the weight of the car.So, basically, this compression decides what the ride height could be, provided other lengths remain constant. What I am doing is changing this static compressed length by actually reducing free length, without changing number of coils in the spring. i.e reducing pitch.So now pitch is reduced. That means the coils are closer to each other (by dX, combined). Earlier the coils could be compressed by X distance after which the coils are hugging each other. But now, since the distance between coils is reduced by dX, the net compression is reduced to X-dX.I hope I am able to replicate the picture I have in my mind.Well, I am not able to imagine at the strut level assembly.In our dampers, we can increase/decrease the fluid pressure in pistons to compress/expand spring.Okay, now I see some relation to your figures. By shifting the spring seat we are able to change the ride height without changing the spring travel, and damping characteristics.In our Formula Student car we can't think of changing the spring seat, for that we would have to change damper mounts (long process). What we do is vary our "Pushrod length" and pre load to achieve required performance.We use Double Wishbone Independent suspension, unlike normal passenger cars which use McPhearson Strut.I was referring to you occupation, Automotive RnD Professional. Edited a line to "correct me if I am wrong" when I found that

The car in question is a Miata Club RF with Ohlins coilovers, but the question could apply more generally to any car with adjustable shocks.  My suspension is the street/track setup with 7k/4k springs, and the adjustment knob on the shock has about 30 clicks that affect both compression and rebound damping. 

Something I've noticed on forums is that people get these adjustable shock setups and use them as a way to change the car's behavior on the street vs. on the track.  The manufacturers are in on the game too, making different recommendations for street or track use.  For example, on my suspension Ohlins recommends 3-7 clicks from full hard for track use, 7-12 clicks from full hard for canyon carving, and 10-20 clicks for regular street driving.

But this goes against everything I know about how suspensions work.  The general approach I've always understood is as follows:

- choose the tires you want to use

- choose your spring rates to be as compliant as possible for the grip the tires provide while staying off the bump stops

- choose the sway bars to complement the springs and avoid funky stuff that happens with too much body roll (camber curves etc)

- choose the shock damping to match the springs and sways, balancing fast weight transfer vs. oscillation

 

So here are my questions:

- Isn't there really one ideal critically damped setting for the shocks given the tires, springs and sway bars you're using?

- Wouldn't that ideal damping setting be the same no matter how you're driving the car?

 

I can see tweaking the damping a little bit to make up for driver preferences.  I can also see it being the 2nd easiest thing to adjust to account for the million little things that aren't linear or perfect on a track car suspension (first easiest being tire pressure).  But cranking up the damping in the shocks for the track just seems like it would make the weight transfer more slowly than necessary on corner entry, and ultimately make the car harder to settle and more unpredictable in transitions.  Am I missing something important here, or is this mostly done by people want their car to feel more "race car" without understanding how suspensions work?

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