Suspension Quad Shocks: Don't Be So Quick To Remove Them

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
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This is one of those Fox body traditions just like the TPS 0.99v myth that simply won't die:

Many claim that with aftermarket suspension components, quad shocks aren't necessary. The truth of the matter is that this is a blanket statement that won't apply in every situation. Therefore, if there is no reason to remove the quad shocks (larger tires for example), then why do it?

Lets discuss what the quad shocks do. Ford has to meet certain NVH requirements on their passenger vehicles. Nobody would buy a new Fox Mustang that rode like a dump truck when brand new, so there was a certain level of compliance in the suspension bushings that was necessary to make the ride bearable. As a result of this compliance in the bushings, the rear axle could move/rotate slightly under load. During hard acceleration, the axle would move forwards and backwards on each side, creating what is known as wheel hop. The quad shocks were Ford's way of slowing the movements down with a pair of horizontal dampeners.

So, install some control arms that limit horizontal/rotational movement and solve the problem right? Not exactly. Not all control arms are the same. Some offer spherical bushings that allow ZERO horizontal/rotational movement, but cause the vehicle to ride like a truck (because: race car). While other control arms do over more compliant bushings made of rubber or poly of varying durometer ratings to retain some level of ride comfort, which may allow for some axle movement.

Long story short, the ability to remove your quad shocks isn't going to solely depend on installing aftermarket control arms, but depends on the compliance of the control arms you install. Not all are created equally. My own combo of Max motorsports HD control arms, with steeda uppers did in fact product wheel hop, until I reinstalled my quad shocks. Someone building a street/strip car may install different arms with spherical bushings at all location and may not need quad shocks at all.

On a street car, it's best to just leave them alone. If you need clearance for tires, try flipping them around first. But at least put in the effort to retain them....and please don't be so quick to suggest that everyone can just ditch them with aftermarket arms

As for cost of new quads, they are pretty cheap. Gabriel 14309 quad shocks can be had for around $20 each. If you need new hardware, they are listed as below.

Quad shock axle housing mounting bolts(12mm x 1.75 x 70mm)

New Gabriel quads installed on my car with MM control arms
img_0158-jpg.575472.jpg


Edit: just to add, pinion angle has been checked and is within spec. While improper pinion angle is proven to cause wheel hop due to axle windup, this post assumes this has been checked and it is within spec. In my case, my pinion angle is good.
 
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For the record, wheel hop destroys the back end of the car.
I think there are more variables at play than just better lower control arms, there are the uppers, the springs shocks and certainly the tires. I've had wheel hop and I've not had wheel hop without them.

I think the rule should be, run them if they fit.

I personally don't see how people can't get them on.
I run a 275 35 18 that measures a real 10.5 inches at the tire.
Clearance at the wheel is at least 3/4's of an inch at the rim.
At the tire which is wider than the rim, clearance remains constant because at that point the quad is just a shaft, the shock body is inside the wheel.
With 17's I think clearance will be close to the same, at 16s it probably starts to tighten up.

The other thing is that the quads and tubs are almost in alignment, so if you hit the quad, you very well will hit the tub too, especially on turning load.

At $40 a set, I think it's a no brainer on a street car.

BTW, the Nut that goes on the stud in the back fits on the bolt listed above.
 
If the OP put a adjustable upper control arm on and set the pinion angle correctly then not only would quads not be needed, wheel hop would be gone.

While I don't doubt that methodology works,
MM suggests using the motorsport uppers on a street car (not a drag car) to prevent bind.
Good adjustable upper control arms with bushings are very expensive.
The ones with heim or spherical? I used a set of those years ago, they ride awful, not doing that again...

The reality is if the $40 quads fix the problem, it's a much easier cheaper solution for the average guy with a street car.
 
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If the OP put a adjustable upper control arm on and set the pinion angle correctly then not only would quads not be needed, wheel hop would be gone.

Pinion angle has been checked and it is correct.

The myth I am trying to dispel is the fact that many assume the moment any aftermarket LCA goes on the car, the quads can be immediately ditched without consequence, especially for those using a street style rear suspension that are not running adjustable upper arms with spherical bearings.

maximum motorsports own advice with their lowers is to install a stock (rubber) style upper that doesn’t offer any adjustability at all.

What you suggest is a bit more advanced that most Fox body owners do to their suspensions. Will it solve the issue? Yes, but most owners probably don't even know such a concept exists nor are they concerned with setting it correctly on their street driven suspension setup running resto-shop house brand control arms.
 
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Put the quad shocks back on if you took them off or don’t have them installed.

The quad shocks are a roll of the dice. No matter what the combination of tires, control arms and shocks, some cars will wheel hop without quad shocks and some won't. There are so many variables in 38-18 year old cars with wear, misalignment and combinations of suspension components and tires that one unchanging answer won't work for everyone.

I personally would install them, and make sure they are in good shape. I do know this, that Ford is cheap. If they could have made changes in some simple component like bushings or control arm construction and saved $10, they would have done it. Multiply $10 times all the Fox body Mustangs ever made and you would be almost as rich as Donald Trump. That's a lot of $$$, and good incentive to engineer something to do away with the quad shocks.
 
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I have a set of fully adjustable team z street beast control arms. Set pinion angle at (1.5*? Not sure pops and one of his friends helped me out here) and I experience slight wheel hop. I removed the quad shocks as they were completely worn out, I needed space for the nitto555 275 wide tires. I may try and reinstall the quad shocks after reading this. However the car does bite hard and traction is wonderful until the tires give.
 
Wheel hop is caused by differential housing rotation. Under acceleration, the pinion gear tries to climb the ring gear, because it can not, the forces rotate the front of the differential upward until the limit of the defection in the control arm bushing is reached, at that point the differential snaps back downward resulting in the dreaded wheel hop. Remove all rotation of the differential and you remove wheel hop. This assumes the upper and lower control arm torque boxes are in good shape.
The quad shocks were added as a band aid "fix" to dampen the control arm bushing defections and thus dampen the effects of wheel hop. As pointed out previously, NVH concerns dictated the use of the type of bushings in the control arms that contributed to the wheel hop.
Tire shake is a completely different phenomenon and is addressed much differently.
 
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Wheel hop is caused by differential housing rotation. Under acceleration, the pinion gear tries to climb the ring gear, because it can not, the forces rotate the front of the differential upward until the limit of the defection in the control arm bushing is reached, at that point the differential snaps back downward resulting in the dreaded wheel hop. Remove all rotation of the differential and you remove wheel hop. This assumes the upper and lower control arm torque boxes are in good shape.
The quad shocks were added as a band aid "fix" to dampen the control arm bushing defections and thus dampen the effects of wheel hop. As pointed out previously, NVH concerns dictated the use of the type of bushings in the control arms that contributed to the wheel hop.
Tire shake is a completely different phenomenon and is addressed much differently.

That still further provides evidence that the nature of wheel hop cannot simply be addressed by just putting on any control arms, as is commonly stated. I think that was the main point trying to be addressed and brought up for discussion and education here in this thread.

In my particular case, I installed new Ford OEM rubber bushings in the axle, and my upper arms are the Steeda versions of the boxed Ford HD arms. All new, but I selected my arms with ride comfort in mind, hence the HD bushings in the MM control arms. So yes, even with new control arms and bushings, my axle still has the ability to rotate because of my choice of arms giving some compliance in order to preserve ride quality. My method of solving it is $40 in quad shocks, which do the job rather well on a car I really only drive to grab a coffee with these days.
 
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If one were to go to solid bushings, IE, spherical rod ends, then pinion angle can be set to 0* as the differential housing is not rotating. Because the differential housing rotates, this necessitates the use 1.5-2* of pinion down angle to prevent driveshaft u-joint bind under hard acceleration. With a solid bushing or rod end installed the obvious trade off is more noise transmitted into the chassis and the cost of replacement as the rod ends would have a much higher rate of wear.
 
Dusting off this old but good collection of quotes:


I was a victim of the no quad shock/ aftermarket control arm wheel hop fiasco... I wouldnt reccomend removing them.

I already have Megabite UCA and LCA. Don't know why I still have wheel hop, trying to figure it out...

[later]...Well, I put the factory original quads back on and fixed the problem. Haven't been to the track but no wheel hop yet.

Thanks for the input everyone.

I have Mega Bite Jr. Lowers and without the quad shocks have alot of wheel hop. Put the shocks back on and no wheel hop at all.

unless there is an elimination of the factory uppers due to the addition of a torque arm or panhard bar the quads should stay. i was one of the victims of the internet myth that when aftermarket control arms are added the quads should go.

I was one of these people that bought into the internet hype of not needing quads once I got control arms.

On my 87GT, I installed Megabite Jr's lowers with FMS uppers and I got wheel hop after I removed the quads. Sometime later I picked up some BBK uppers and lowers and also got wheel hop without the quads. BAD wheel hop at that. I installed the quads and it improved.

I've got Steeda uppers & lowers. But I still get some fishtailing when I drive irresponsibly--HA, so I just bought a set of Gabriel quads to replace my well-worn (108K miles) stockers---they DO make a difference.

My 88 GT had Steeda Aluminum LCA's, stock uppers and wheelhopped bad enough to break one of the parking lights without quads, with quads it was smooth.

I had baad wheelhop with FRPP HD uppers/no quads. Put in quads, and the wheel hop was gone.

I had really bad wheelhop just in street driving. I replaced control arms and the wheel hop stayed the same. I replaced my quads with Koni ones that I found on E-bay cheap and the wheel hop went away. Traction got much better too. New Quads were a great improvement on my car.

I have always heard toss them when you get "real" control arms. I spent close to $100 to go to a track rental this spring, and I almost took the quads with me just in case...The track was good, but my car was wheel hopping bad in 1st and 2nd. So be careful with that conventional "wisdom" that they aren't needed once you change out your stock control arms... My car wheel hops like a bitch without them.

OK a buddy was driving my car the other day and he started doing a burnout and the car was wheel hopping a little bit.
I have UPR Double Adj. uppers, Jegs Lift Bars, 03 GT rear springs and 50/50 Lakewoods...Also long gone are the quads....Why am I having wheelhop?

Glad I'm not the only one [who got wheelhop without the quads]. I have Granatelli/JD's performance arms and I had terrible wheel hop last time at the strip. 60' was 1.81 when I had the quad shocks, dropped to 2.05+ with them off.

I removed my quads when I replaced 6 of the 8 bushings in the rear with poly bushings and had to reinstall them because of the wheelhop. :(

I noticed that when i installed a set of steeda upper and lowers I experiened alot of wheel hop after removing my quads.

I just installed some lower control arms, and they didnt help at all! I still have wheel hop....

...its a 88 LX i put on JD's performance control arms. I have always heard that you leave the quad shocks off when putting on lower control arms...

[later]...put the quad shocks back on and tightened up all of the bolts, my wheel hop is almost gone...It's interesting how after putting on the quads with the new Control arms, my tires actualy squeal instead of just jump.
Pretty exciting :)

[later still] Lemme just say thanks again to MFE, and all of the other guys who gave me advice to stop the wheel hop. Its totally gone now. All it took was 5 minutes bolting my quads back on and the wheel hop started fading fast. I think as the parts are wearing in its getting even better. At first I had a little bit of hop, but I took it out today and I couldnt get it to hop at all. Thanks again guys.

just an update...

I replaced the quad shocks with the Gabriel #14039's that MFE recommended and the wheel hop has been eliminated! The old quads were in terrible shape, and I'm glad I've replaced them. I'm accelerating much smoother now with no hiccups whatsoever.
 
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Add me to the list - I put quad shocks back on my car last year after 15 years. It seems to have improved both forward traction and handling. I put them on after dealing with some wheel hop issues last summer.

Another thing to check if you have wheel hop problems is your upper shock bushings. If they are soft or damaged, that can add to the wheel hop issue. Poly replacements are dirt cheap too.
 
There is truth to both sides of the argument. I ditched the quads with my old suspension set up, then added fresh ones back to help the wheel hop.

However, after going to my new suspension setup, with better parts and actually setup correctly, I no longer need them. But my newest setup is Definetly one track minded as it does not provide a smooth ride.

Joe