Calgary Jeep Association
4x4 Related Groups => Tech Talk => Topic started by: Fredduck on March 24, 2008, 07:53:54 PM
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I've mounted my shock tabs and front towers. The measurements are 22 inches front and 2o inches in the rear from mount point to mount point, now these measurements are with out drive train and body.
The engine and drive traindrop the frame about 2 inches.
What lenght of shock should I order? Also I plan on installing boomerang shackles on the rear.
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COMPRESSED DIMENSION
To figure the compressed dimension, take an eye-to-eye (stud-to-stud) measurement with the truck at rest. From this dimension, subtract the distance between the bump stops. This is your nominal compressed dimension. It is also a good idea to go at least 1/2" shorter to allow for bump stop compression.
This assumes the shocks are mounted vertically and the axle also moves vertically. In cases other than this, the shock movement will generally be less.
If possible, shock measurements should also be taken with the axle at full compression to ensure dimensions are correct. This can be done by twisting up the suspension on a ramp or obstacle, or articulating the suspension by some other means.
Extended Dimension
Next, jack up the vehicle, or somehow twist it up, to see how much droop you get (with the original shock disconnected). It may also be helpful to disconnect your sway bar as well.
On leaf spring suspensions, you may see the maximum droop as the point where you run out of spring/shackle length and the axle cannot drop any further. Or.... you may have other limiting factors such as tire interference, spring bind, etc.
Get an approximate length from this and then start checking for shocks of the appropriate length in a shock vendor catalog. You may find a shock that matches your range well or you may have to go through a few iterations of comparing available lengths and your travel movement, and possibly consider modifying your existing shock mounts to maximize your shock travel.
Extended Dimension
A FEW OTHER NOTES........
If you are cutting the dimension close on either compression or extension, note also the effects on movement of the shocks leaning forward or backward, as their travel distances will be different.
For instance, for a given amount of rear axle droop on a vehicle with leaf springs (rear mounted shackle), the shock leaning backwards away from the axle will travel more during droop than will the shock leaning forward
i have:
2 new shocks that are 16" eye to eye compressed and 26" extended
2 new shocks that are 16.5" eye to stud compressed and 27.5" extended
let me know if your interested!! good luck :)
Dave
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Thanks Dave,
I'll get the forklift tomorrow, I dont think I can compress the front anywhere near what the numbers your talking.
Thanks again for the tech
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There are a few of the shock websites that have their extended and compressed lengths listed. I know Rubicon Express and Rancho do. I think that I dig up the OME lengths both regular and long travels. I would just have a look through these and see what shock length would work best.