Rear shock mount locations: Center vs. stock position.

[Yota Up]

My buddy is telling me to weld on some new mounts for the rear shocks, but to put them in the middle, so each shock pushes "out".
I was going to just use the stock mounts and weld on new brackets onto the diff directly, or the plate of the U-bolt flip kit.

I'm concerned that having both go up to center may let it wobble side to side too much.  Since I don't know what I'm talking about, I'm asking ya'll.

Cheers!

[Birfailed]

You'll get the most dampening out of your shocks the closer you get em to your tires, and the more vertical you have them helps too.  If you mount em tipped in at an angle you can gain some more travel out of them, kinda...no matter how you mount a shock you never can gain travel from that shock, but depending on the way you mount em you can use the length of the axle tubes to kinda gain travel.  Ya dig?  I can't explain things very well.  Example: a 10 inch shock mounted vertical, and mounted at it's half travel point has 5 inches of droop and 5 of up travel.  Now mount the same shock at a 45 degree angle tipped in toward the center of your frame, now your axle could move 7.5 inches up and 7.5 inches down without bottoming out or topping out your shocks.  And your concern for side to side wobble?  I really hope your shocks don't have anything to the placement of your axle.  That's what your leaf springs do, hold the axle center, locate the axle.  Shocks only dampen, without them your springs would just bounce and bounce, the shocks just smooooth it all together.

[toynorcal]

Well, you wont notice nuch if any difference in the ride by mounting your shocks at an angle compared to stock location. But when you articulate and bottom out the shocks in the stock locations, you will. To keep the best ride, mount your shocks as far from the pumpkin and with as little angling as posible while still allowing full articulation.

[FIREBALL]

These guys are right on. For the best dampining and body roll control the shocks should be vertical. But, if you are trying to get a lot of articulation the a vertically mounted shock would have to be really long and would have to come up through the bed. So, to get as much articulation as possible without shocks poking through the bed you can run a shorter shock at an angle.
Also make sure that your shock mounts/bolts are facing front to back so that as the axle articulates the shock will pivot on the bolt. If your bolts are parallel with the axle like stock then all the twist during articulation will have to be taken up in the bushings which will limit travel and wear them out quicker.

[tufsurf]

from tallchevy350 in rig gallery


Built the rear shock mounts this weekend   I didn't want to relocate load valve or remove it. I welded 2" tube from the fuel tank x-member to the rear x-member, notched a plate & wedled that to the tube & made the mounts on the axle. It's hard to see but I recycled parts that I cut off to make the axle mounts. They are made from the rear spring front hanger. I just drilled the holes larger to fit the bolts & ground them to match.   

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rear shocks.jpg (30.36 KB, 640x480 - viewed 51 times.)

[Loki]

this works really well for stability and flex

[FIREBALL]

That looks good! But is there a body lift helpin out with the clearance there?

[BigMike]

You'll get the most dampening out of your shocks the closer you get em to your tires, and the more vertical you have them helps too.

Actually the more vertical they are mounted is how you maximize their dampening effect.

If the shock is mounted vertical, then the distance the shock piston moves is at its greatest, thus the shock is able to work against the oscillations for the longest possible amount of time.

The more you lay down the shock, the less the shock piston moves, and less work is done against the oscillations by the shock.

It is simple trigonometry. The sine of 90-degrees in the y-direction is 1, whereas the sine of say like 45-degrees in the y-direction (projected above the x-axis) is only 0.71.

So regardless of what the dampening force of the shock is, it is greatest when multiplied by "1" rather than by "0.71".


The reason you can get more articulation when the shocks are layed down is also simple trigonometry. If the shock is vertical, and the axle moves 5-inches of up-travel, then the shock will be compressed 5-inches times "1" = 5-inches.

But if the shock is mounted at 45-degrees above the x-axis, and the axle moves 5-inches of up-travel, then the shock will be compressed 5-inches times "0.71", which is only 3.55-inches.

In order to get the 5-inches of shock compression when mounted at 45-degrees above the x-axis, you'll need to compress the suspension by 7.04-inches of up-travel.

So in this example, if you mount your shocks at a 45-degree angle, then you will gain 2-inches of up-travel compared to if you had the shocks mounted vertical.


So it's a compromise: In one situation you have more dampening, and in the other, you have more available suspension up-travel.

BigMike

[FIREBALL]

Way to go there math boy....we already said the same thing without the trig. Now get up here and help me with my sand rail.

[Loki]

That looks good! But is there a body lift helpin out with the clearance there?

Lets just say that my buddy installed one on his truck with a 1" body lift and eurethane bushings...he has about 1" of clearance between the top of the hoop and the bottom of the bed.

Now this has to do with where you position and weld this hoop but not if you have 14" bilsteins and try to make this item fit, you'll have to run your shocks at more of a 50 degree angle which is a bit extreme and would require welding bolts to the new hoop. if you do this, i would suggest getting 12" long travel shocks and centering it over the axle and in the middle of your frame rails. 14" long travel shocks are too much, but the 12's are perfect.

and damn BM...thanks for the trig lesson

[Burl]

I have a similar setup but no body lift on my 85 4 runner.  Instead of round pipe I used square tube.  I had to notch the tube to fit in between the body and frame.

That looks good! But is there a body lift helpin out with the clearance there?

[FIREBALL]

Ya, I was runnin 9012's on my mini and 14" bils on my runner and I think I would have been better off with a little shorter shock on he runner. It was even a little steep on the mini, but it was also a lot lighter in the rear than the runner was and neither one had a body lift so it definetly reduced the available space.