multiple upper shock mount positions

[andy16]

how much would moving the shock 10 degrees from one upper postion to another change that "spring" keeping the ride height the same. going from more st8 up to more angle. i know itb be softer but is there a formula thanks

[twisterf5]

25lbs most of the time

[talclipse]

I think what you are talking about is the angle correction formula (ACF).

The formula is: ACF = cosine * angle of the shock

You then multiple this times your spring rate and that will tell you what spring rate the car "sees".

You can also use pro's calculator: http://www.proshocks.com/calcs/anglefirst.htm

[Matt49]

I think what you are talking about is the angle correction formula (ACF).

The formula is: ACF = cosine * angle of the shock

You then multiple this times your spring rate and that will tell you what spring rate the car "sees".

You can also use pro's calculator: http://www.proshocks.com/calcs/anglefirst.htm

That gives you the effective spring rate at the point where the spring contacts the lower control arm. To get the true effective spring rate (what the wheel sees) you must multiply that by the square of the motion ratio.
The motion ratio is the distance from the shock mount to where the control arm mounts to the chassis divided by the distance from the ball joint to where the control arm mounts to the chassis.
So if you have 400 pound spring leaning in at 10 degrees, an 18 inch control arm, and the distance from the shock mount to where the control arm mounts on the chassis is 15 inches, the formula looks like this:
Effective Spring rate = (spring rate)*((MR)^2)*(ACF)
Effective spring rate = (400)*((15/18)^2)*(.985)
Effective spring rate = (400)*(.694)*(.985)
Effective spring rate = 273.4

[Matt49]

I also would like to make note that the ProShocks calculator is wrong.
All that the tool does is take your desired spring rate and divide by the "number" that they provide in the chart to tell you the spring that you need. That would work okay if the numbers were right but they are not. Those numbers should be the cosine of the angle...clearly they are not.

[talclipse]

I also would like to make note that the ProShocks calculator is wrong.
All that the tool does is take your desired spring rate and divide by the "number" that they provide in the chart to tell you the spring that you need. That would work okay if the numbers were right but they are not. Those numbers should be the cosine of the angle...clearly they are not.

I should have proof read the pro site a little better. Thanks for catching that!

[andy16]

its like algebra 3 all over again lol, im glad u guys on top of that thanks for the help, i have multiple shock mounts on front and rear and im assuming i can move the shock angle instead of changing springs was that the idea behind this?

[7uptruckracer]

The fronts could be if its a wide RF option car...so when you put the longer lower on you can keep your shock angle the same.