The Stovebolt Site Forums The Shop Area Driveline Rear shock angle 1950 chev truck with 56 differential

I am wondering what appropriate angle should my rear shocks be at. I am using the rear axle conversion kit to install 1956 different on my 1950 truck . I am putting the leafs below the axle to keep stock height, I have not secured top shock mount yet but looks like if I put close to stock it would be 62 degrees. I read on previous forums 45 would be probably the best?

Rick, do a search for shock mount angle. I asked the a similar question early last year and it led to several responses. The stock mounting angle should work well, shocks are only there to dampen the spring rebound.

Yes it was a hot debate. Feathers were ruffled. I think the final statement was:

The shock at 45 degrees, the travel is less and the dampening is less.
The shock at 90 degrees, the travel is more and the dampening is more.

As long as the shock doesn't bottom-out or extend past it's maximum limit.

Well then maybe 67.5 is the way to go

Some people don't understand geometry. Somewhere between 45 and 60 degrees gives the longest shock travel, which equates to more dampening, not less. Be aware that the angle is constantly changing as the rear end moves through its range of motion.
Jerry

After owning/driving AD trucks for 50+ years I'll add the rear axle when coupled with the stock leaf spring scheme (what it appears you have) in normal driving does not move up/down nearly as much or as freely as you might think. Very stiff, actually.

Now a 1965 pickup I owned for a summer was a completely different thing. In ways it rode more like a car. The rear moved up/down much more easily within the first 2 inches of spring travel. Driving through curves, you could actually feel and see it wallow in the rear. If two guys stood in the back and jumped up and down, the rear would bounce easily. When you hit the brakes, the front would stay pretty well level, but the back would elevate on you, giving an odd feeling of loss of control at any speed over 50. But if you loaded the bed (say with firewood), once it compressed past about 2 inches, you got into the "meat" of those rear coils and then it actually rode like a truck.

Buoymaker, you were right the first time, the farther away from 90*, the less effective the the shock is. This is a chart more then one of the aftermarket suspension companies use.

That figure isn't correct. For the same amount of suspension travel (vertically), a vertically mounted shock travels exactly the same amount. If that same shock is mounted at 45 degrees, the shock compresses ~1.4 times farther than the vertically mounted one. And 1.4 times faster. Since shocks work on a compression velocity principle the shock mounted at 45 degrees will have more resistance.
45 degrees is the sweet spot, and the compression distance decreases if mounted closer to horizontal. In the extreme, if a shock is mounted horizontally, it will have zero compression as the suspension compresses.

I think the key is the word efficiency in the graph - and I'd posit another alternate, effectiveness. A shock cannot be designed and engineered at an angle other than vertical (it could but, since all shock mounting situations are different what angle would they pick) Most OEMs and shock manufacturers thus assuming the shock was designed to be most effective at vertical and so everyone works around those assumptions. However this rational only exists in my mind to justify the above graph and understanding - shocks are best installed as close to vertical as possible.

Plus there are other factors to the shocks performance besides it cycling velocity. As it moves farther from vertical it takes less force to compress it.

The angle, velocity, travel amount, force and spring rate are all variables a particular shock has to contend with in addition to similar size shocks (length and diameter) with different valving characteristics. You could mount a shock at 45 degrees and have it perform acceptably as long as it is sized and valved accordingly.

Note the suspension travel vs. shock travel in the chart. If the suspension compresses x amount but the shock only compress a portion of that, then only a portion of the potential amount of fluid is flowing through the valving to dampen the motion (regardless of the velocity with which it does it).

In this specific instance, the amount of travel is already determined by the springs and bump stops. You would want to mount the shock at a "reasonable" angle so that the shock is essentially nearly fully extended when at full droop and nearly completely compressed when on the bump stops. I would recommend somewhere close to factory, unless you want to do a bunch of trial and error with different mounting angles, shock sizes and valve characteristics.

Use the KISS principle. When I bought my Camaro rear axle, I grabbed the shock mounts along with other parts. The shock mounts have the angle set. I just followed that angle when I set up the shocks. IOW, the angle is the same as the factory Camaro. You have to trust the GM engineers. This does mean that I have 1 shock leaning forward and 1 shock leaning backward.

I like this 2009 response from enginejo (jalopyjournal.com):

Shocks are most effective when mounted the same as the direction of deflection. So in theory, you would mount them vertical. But if you do, they do not resist axle windup forces created by acceleration and braking, or side to side forces from body roll. Angling them forward helps resist axle tramp caused by acceleration, but not braking. Staggered shocks, one forward, and one back, resist both braking forces, and acceleration forces, as well as controlling bounce in the springs. And angling them in too, helps resist body roll, although the current thinking is to control body roll with a sway bar.

Another reason for angling the shock, you can mount a longer shock in the same vertical space, so for every inch the axle moves, the shock may only move 7/8". This does make the shock less effective, but you can use a stiffer shock to compensate. On a light car, where most shocks are too stiff to begin with, this can work in your favor. This allows using a longer shock on a lowered car without limiting axle travel like a short shock would.

The closer a shock is to the wheel it is controlling, the more effective it is, because the leverage of the wheel is less against the shock. When a wheel bounces, the fulcrum of the lever is actually the opposite wheel.

The more a shock is angled to the direction of the force acting on it, the less effective it is. Vertical to the force, it is 100 percent effective, 45 degrees to the force 50 percent effective, 90 degrees to the force, 0 percent effective. Most shocks are calibrated to be run at 15 to 20 degrees from vertical.

My input:

In a nutshell, one has to choose. I would think an AD farm truck would be designed for hauling and not jack rabbit acceleration and expressway stopping.
I did read it is best not to tilt the shock in two directions. Example forward and inward.