Suspension Pro- A little help please

[Clois Harlan]

I may need to relocate my rear shock top connecting points. I understand that if I move my locating points inboard by 5 degrees I will change the length of my shock but also the load on my springs by a certain fractional amount (I don't have the table with me). Other than the length and weight considerations are there any significant disadvantages/advantages to increasing the angle of your shocks inboard by 10 degrees or so?

Are there any handling issues that result from such change?


Thanks


Clois

[Morris]

Clois

When you change the angle of that shock and it's a coil over......

You have changed the wheel rate ...as in the calculation..... you use the Cosine of the angle of the shock to calculate wheel rate.....

And wheel rate is more important then springs.....

Morris

[G.R.]

Originally Posted by Morris

Clois

When you change the angle of that shock and it's a coil over......

You have changed the wheel rate ...as in the calculation..... you use the Cosine of the angle of the shock to calculate wheel rate.....

And wheel rate is more important then springs.....

Morris

And in "English" for those of us that are not engineers or versed in the technology...Please Morris explain what you mean...I'm confused

[Morris]

G.R.

The formula for wheel rate is

= (Motion Ratio) Squared X Spring Rate X (Shock Angle Cosine) Squared

The reason is because the spring is not right on top of the tire.....

So you have to know the Wheel rate numbers instead of the spring rate number.....

All suspensions are different and have different mechanical leverages on the spring.....

So knowing the wheel rate is more important then knowing the spring in your car.....

On a CSX or Kirkham....if you look at the lower control arms(front and rear)....you'll see that the coil over mounts in different locations on the control arm.....

And when you calculate the wheel rate out with 600# springs on the front it calculates out to around a 210# wheel rate......

And the Rear with a 500# spring calculates out to around a 335# wheel rate.... which is why you have to have a larger front Anti-Roll bar on the front....so when your chassis moves the rate goes up because you add the wheel rate and the roll bar rate together to get the actual wheel rate.....

The actual force on the tire/wheel from the chassis....

That's why it doesn't matter when someone asks about what springs are you running...... the mechanical leverage is different and will give a different wheel rate.

Hope this helps out....

Morris

[RedBarchetta]

I have a similar question/concern, but I was a B student in high school physics so all this talk is still too much for me to process.

Morris (or someone else with this knowledge), can you please explain to me the effect on handling (lateral) and traction (straight line) I would experience if I relocated the upper rear shock mounts INWARD slightly? There are three mounting points in/out on a Superformance and my car presently utilizes the center hole. The inward hole is roughly 1/2-3/4" away.

I'm getting ready to install fatter rubber, and although my preliminary calculations do not indicate any interference between tire sidewall and coil-over, IF I have to make an adjustment I would at least like to understand what effect this will have on lateral grip vs. straight line acceleration. My intuition tells me that the flatter the shocks are set, the better the lateral grip will be but at the cost of straight line traction (i.e. less downforce/stability to handle the shock load of hard acceleration).

Am I on the right track?

Thanks,

-Dean

[Tommy]

Dean -
Here is my very amatuer answer to your question. If relocating your coil-over shock results in it moving farther for each inch the wheel moves up and down, you have effectively increased both the spring rate and shock absorber rate. If would be like putting in stiffer springs and shocks. If the relocation results in the shock moving less with each inch the wheel moves, the result will be the opposite. Whether the result is good or bad depends on whether the spring and shock rate was where you wanted it in the first place. Again, I am just a fellow amatuer, so get another opinion please.