Rear Coil Over Shocks location

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Brad4406

Brad4406

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I've seen a few cars lately with the rear shocks mounted in front of the rear axle, as opposed to what I had always seen before with them mounted behind the rear axle. What advantages would there be for mounting them in front of the rear axle instead of behind?
 
Depending on your set-up, one benefit for mounting the shocks behind the axle is that during extreme acceleration (drag launch) the axle tends to want to rotate top forward. If you are using the stock leaf spring set-up mounting the shocks behind the axle will help dampen the torsional effects by acting in compression.

If you have a 3 or 4-link set-up the upper bars restrict the rotation, your shocks are really only dampening the effects of bump oscillation. Remember the springs do all the work, the shocks dampen the rate of how fast a spring compresses or extends to control wheel hop, squat or dive.
 
Hyper-Performance said:
Depending on your set-up, one benefit for mounting the shocks behind the axle is that during extreme acceleration (drag launch) the axle tends to want to rotate top forward. If you are using the stock leaf spring set-up mounting the shocks behind the axle will help dampen the torsional effects by acting in compression.

If you have a 3 or 4-link set-up the upper bars restrict the rotation, your shocks are really only dampening the effects of bump oscillation. Remember the springs do all the work, the shocks dampen the rate of how fast a spring compresses or extends to control wheel hop, squat or dive.
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I'll be running a 3 link set-up. I plan to mount mine behind. I really don't see any benefit to mounting them in front of the axle as I have seen recently. According to the information you provided, it doesn't appear that there is any benefit for my application.

Thanks.
 
It is done to limit axle wrap as the axle wants to rotate in the opposite direction of tire travel. The way Chrysler assembled leaf springs (assymetrical with extra beef in the shorter front segment) acted as a sort-of traction bar. Using the shock to slow axle wrap is why they would be mounted forward of the axle. On some performance Fords you will see one shock forward and one behind. That is to aid traction and control axle wrap.
 
The coil overs on the 4 link I have are forward of the axle. The top of the axle wants to rotate backward on acceleration and having the coil overs in front help resist that rotation.
 
here I thought it was because with a stock gas tank, there isn't enough room. The spring on the coil-over makes the package a lot larger in diameter than a std shock.
 
Hyper-Performance said:
You are correct Sir! I miss-typed....the rear end reacts in the rotational direction towards the shock to put them in compression during hard launch with the shocks rearward of the axle.
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Don't you mean forward of the axle? Rearward would put the shocks in less compression on launch than if installed in front.
 
HemiDenny said:
here I thought it was because with a stock gas tank, there isn't enough room. The spring on the coil-over makes the package a lot larger in diameter than a std shock.
Click to expand...

Actually I believe that is a legitimate reason. I was told they won't fit with a stock tank.
 
clinteg said:
Actually I believe that is a legitimate reason. I was told they won't fit with a stock tank.
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my coil-overs just barely fit....and that is AFTER stretching the wheel openings 3" to the front and moving the 8.75 housing about 1.5" forward.
 
HemiDenny said:
here I thought it was because with a stock gas tank, there isn't enough room. The spring on the coil-over makes the package a lot larger in diameter than a std shock.
Click to expand...

That may be part of it, but how many people going that far are running a stock tank? I've used the cheap coil-over kits when I didn't have time to fix sagging leaf springs. They fit with the stock tank, but they aren't as large (I believe) as the aftermarket shock/spring parts.
 
I have coil overs on my Dart Sport, 8 3/4 and they clear the tank, but hit the back brace slightly.
 
Bad Sport said:
I have coil overs on my Dart Sport, 8 3/4 and they clear the tank, but hit the back brace slightly.
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that is good to know.


I would prefer a rear mounted coil-over shock for a 4-bar package I have on the drawing board. Perhaps with no panard bar as I have it is workable.
 
With a ladder bar set up, no leaf springs, and a diagonal link, what would be the benefit of mounting them in the front of the rear axle? Shouldn't the ladder bars prevent axle wrap? I would think it would be the same for a 4-link set-up and wouldn't matter whether they were placed in front or behind.
 
Brad, you are correct. Leaf springs are an inexpensive method of mounting and controlling the rear end, but as found in many cars (symmetrical - same length front/rear of the axle) they are prone to allow axle wrap and wheel hop. That's why Chrysler leaf springs work better. Trailing arms (which ladder bars and other setups are) work better as far as axle wrap (and are more tuneable), but need more pieces to keep the axle located side-side properly.
 
Brad4406 said:
I'll be running a 3 link set-up. I plan to mount mine behind. I really don't see any benefit to mounting them in front of the axle as I have seen recently. According to the information you provided, it doesn't appear that there is any benefit for my application.

Thanks.
Click to expand...

If you are going to run something similar to this maybe they are moved in front to clear the panhard bar.
 

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you are on the money..

mine is a 4-bar, equal length bars and can run parallel for street and as either a 32". 36" pr 40" bar with an appox 8" instant center ....but not triangulated, so I run a panard bar behind the coil-overs. It is tight even with the 1.5" forward mod. When I built it I wanted to leave plenty of room for tailpipes.. I understand tailpipes are usable on some of the triangulated set-ups out there....but I didn't want to complicate it more than it already was.

of course, the advantage of a triangulated set-up......is NO centering device needed (panard bar, lateral link, etc,)
 
Bad Sport said:
If you are going to run something similar to this maybe they are moved in front to clear the panhard bar.
Click to expand...

Wow, I hadn't even considered that. I'll have to look through those photos I had previously seen.

Since I don't have to worry about a panhard bar or stock gas tank, I guess I'll stick with behind the rear axle.

Thanks.
 
Well, I just discovered another reason to mount them in front, at least in my case. I moved the rear axle back so that it's centered in the wheel opening; it doesn't leave room to mount them behind the axle now as it interferes with the floor.
 
And now you have stumbled on one of the biggest reasons things were done at the factory, because the designers did their job first and the engineers had to make sure the stuff fit...
 
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