Thread: Shock Geometry

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Originally Posted by Bob Parmenter

Had a little more time this morning to do some searching. I couldn't find the original chart I recalled, but found this that is similar in it's discussion; http://www.4x4review.com/feature/shock-genius.asp
About a quarter of the way down the page is the discussion on geometry.

For the sake of discussion, That article is good, but seems to be aimed at 4wd vehicles... Would you want the shock on the front of the straight axle to behave in the same manner as the shock on a 4wd axle??? Geometry is geometry, but wouldn't you be looking for the shock to do different things on the two vehicles? The part of the article that I consider important for any vehicle is to have the shock as far outboard as possible....I would imagine something to do with getting the energy created by tire when it encounters irregularities in the road surface(or track) transferred into the shock and dampened before it travels any great length through the suspension components? Seems I recall the old gassers having the shocks on the rear of the axle and angled back to the top mount?????

According to what I read, would the correct placement of the shocks being on the shackle side (forward in this case) of the axle????

In the matter of a "solid" axle I'd say yes they are very similar in that the entire axle will move to some degree with deflection at one end, as opposed to say IRS where the side deflected will move independently from the other. Though I used that article mainly for the geometry discussion, not matters specific to 4x4's, since it was a quick find just to put a known number to loss of effectiveness. And yes, I would agree that the shock should be mounted to the front of the axle here since the axle will move slightly forward because the shackles are at that end (as opposed to the other end being fixed mounted I presume). Which would in turn argue for the top mount of the shock to be somewhat forward of the lower shock mount, though there's probably enough movement in the shock bushings to deal with the slight movement of the axle (unless those springs are really soft).

And just to continue for the sake of discussion, the needs of a drag car will differ from a street machine in that the front axle, once the entire suspension is dialed in for traction purposes, pretty much only goes up and down in unison (left to right, unless there's a lot of chassis flex), so accounting for the arc of either end as opposed to it's opposite should be a non-factor (well, except when turning onto the return road or unintentionally going off road ) All that being said, 10 degrees of inclination only costs 2% efficiency.

Thanks for the informative discussion guys. With only a slight loss of efficiency, and the added benefit of greater stability, I have decided to go with the angled mount. And I hope nobody else has good reasons against it, because, I already took it into the welder. My Lincoln does not have enough juice for for that heavy Iron bar!