[supercars]

How do you decide what is the correct setup for the vehicle ?

I have an adjustable shock absorber from Gabriel USA.

There are 3 possible settings on it. 70-30, 80-20 and 90-10.
Which should I choose ?

Please advise.

[SS-Traveller]

What vehicle? Which specific shock absorber? What kind of usage (load, load distribution, type of road, etc.)?

[Mpower]

Sounds like a drag racing shock?

The first number is the shock stiffness in bump (wheel traveling up) and the second number is the rebound (wheel coming off a bump). For street useage, I would pick 70/30

[Rehaan]

Originally Posted by Mpower

Sounds like a drag racing shock?

The first number is the shock stiffness in bump (wheel traveling up) and the second number is the rebound (wheel coming off a bump). For street useage, I would pick 70/30

What do these numbers represent? Some sort of resistive force? Are they measurements in a particular unit?

How come as the bump number goes up, the rebound number comes down? I would have guessed it would go up too?

cya
R

[Akshay1234]

Those seem like compression/damping/bump and rebound settings. I don't have technical knowledge on this, but from what it seems to me. The first setting is the stiffest and the third is the softest.

[Mpower]

Originally Posted by Rehaan

What do these numbers represent? Some sort of resistive force? Are they measurements in a particular unit?

How come as the bump number goes up, the rebound number comes down? I would have guessed it would go up too?

They are ratios (add up to 100) of the split between bump:rebound

This looks like drag racing lingo (I've never used it personally)...& the product is designed for a very specific purpose.

The shocks that are specced for road going cars typically have compression and rebound forces specified in Newton as a function of piston speed. Hi, mid and low
High speed is 'ride motion' and low speed is 'body motion'. For plush ride you want the shock to have low forces at high speeds and high forces at low speeds.

Secondly, the shocks are valved such that forces in rebound are typically 3 times higher than bump. (bump and compression are the same thing BTW)

Clear as mud lol?

[Mr.Boss]

those numbers must be the ratio of bump stroke against rebound stroke.
Just made a simple sketch to explain the same.

BTW, for which vehicle?

[Mpower]

Originally Posted by Mr.Boss

those numbers must be the ratio of bump stroke against rebound stroke.
Just made a simple sketch to explain the same.

So, you're saying one can change the ride height of the vehicle by adjusting the shock setting?

I dont think so!

[Mr.Boss]

Originally Posted by Mpower

So, you're saying one can change the ride height of the vehicle by adjusting the shock setting?

I dont think so!

Possible!
I couldn't explain now as i'm posting from mobile, soon i will explain more clearly

Using the same spring if you could adjust the position of lower spring seat, ride height can be adjusted

[Mr.Boss]

Originally Posted by Mr.Boss

I couldn't explain now as i'm posting from mobile, soon i will explain more clearly

Using the same spring if you could adjust the position of lower spring seat, ride height can be adjusted

Better Late then Never.



In the above snap Spring, damper outer tube and piston rod, spring seats remain same. The only change is Lower Spring seat position, by changing which one could adjust the ride height, compromising the Bound-Rebound stroke ratio. Which in turn will affect the ride & handling characteristics and relative parts life (Tire, steering & suspension ball joints, bushes, and the damper itself)

[Ashir]

Originally Posted by Mr.Boss

Better Late then Never.

Attachment 1335660

In the above snap Spring, damper outer tube and piston rod, spring seats remain same. The only change is Lower Spring seat position, by changing which one could adjust the ride height, compromising the Bound-Rebound stroke ratio. Which in turn will affect the ride & handling characteristics and relative parts life (Tire, steering & suspension ball joints, bushes, and the damper itself)

Actually the lower spring seat should also remain fixed if it also has "Damper". What changes ride height is the static compressed length. The length of spring is changed by inducing initial compression (perhaps called "clocking"). The stiffness of the spring remains unchanged, if it is not variable stiffness spring. Stiffness is a material property.

By changing the initial compression, total length of spring decreases, thus maximum bump and rebound possible is reduced (Spring Travel)

Please correct me if I am wrong.

Few pics to explain:
[Damper - Kaz Technologies; Software: Solid Works (lic. to Team Fateh)]







PS. Just saw your job Mr.Boss

[Mr.Boss]

Originally Posted by Ashir

Actually the lower spring seat should also remain fixed if it also has "Damper". What changes ride height is the static compressed length. The length of spring is changed by inducing initial compression (perhaps called "clocking"). The stiffness of the spring remains unchanged, if it is not variable stiffness spring. Stiffness is a material property

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

Originally Posted by Ashir

PS. Just saw your job Mr.Boss

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

[Ashir]

To Mod: Might consider shifting this thread to "Technical Stuff"

Originally Posted by Mr.Boss

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.

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.

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.

Originally Posted by Mr.Boss

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

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.

Originally Posted by Mr.Boss

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

I was referring to you occupation, Automotive RnD Professional. Edited a line to "correct me if I am wrong" when I found that

[Mr.Boss]

^^^
My bad. I had something in mind and posted something else. Thanks for correcting in pitch & no. of coils part. I stand corrected.

Your explanation on changing the initial compression stands good for project cars. But in case of after market stuffs available for road cars, spring (free) height remains same and the ride height is adjusted by lowering / raising the lower spring seat position. Regarding the stiffness part, though the coil spring may have a linear stiffness characteristics, at vehicle level the load-deflection curve will not be linear (due to additional parts stiffness contribution - like bumper bounds, suspension bushes, etc)