Quad shock mounting location

joekurt

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Oct 28, 2021
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I am building a kit car that uses a ‘90 Mustang rear. As you are aware, that car had a 4 link rear suspension and used horizontal Quad shocks to control wheel hop. I want to keep the Quad shocks but the kit chassis rails are 5” - 6” inboard of the original Fox body attachment points.
So here’s the question, can I move both mounting points for the Quad shock towards the center of the car and still have them work correctly? That would place the Quad shocks about 13” to either side of the car’s centerline and keep them horizontal to the ground. I plan to weld a new mounting point on each axle tube and a matching moun ting points on the undersides of the chassis rails towards the tail lights. Thanks for any help!
 

joekurt

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Oct 28, 2021
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Not using after market control arms. Anyway, it seems to be a controversial subject. Some say get rid of them; others say as soon as they did they had wheel hop again. We'll be putting about 400 HP to the rear wheels on a 2,400 lb car. Seems like the quad shocks are the right way to go.
 

WhiteCobra95

Mod Dude
May 2, 2006
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Quad shocks are a fix for wheel hop, essentially covering up for flexible factory stamped LCAs with soft rubber bushings (designed for noise and ride comfort rather than performance). If you are making that much power and can fit factory control arms, you would be much better off going with aftermarket LCAs from a good brand like Maximum Motorsports or Steeda. Most people ditch the quad shocks when using aftermarket LCAs because they're no longer necessary, quad shocks are extra weight, and they limit the whee/tire size that you fit. Search the internet for pictures - the quad shocks run parallel to the ground with one end attached to the axle housing and the other attached to a large stud on the unibody.
 
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joekurt

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Oct 28, 2021
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Thanks WhiteCobra95. We probably will go with aftermarket control arms. But I still would like an opinion on actually moving those quad shocks inboard with 2 new mounting points welded to the axle tube on each side. Don't know why Ford put the rear mounting point so close to the axle flange. If we cut them off and weld a new ones 8-10" closer to the pumpkin, it lines up perfectly with the kit chassis rails (where we will weld the other mounts) and keeps the quad shock perfectly level to the ground. But it makes me wonder if Ford put them so close the ends of the axle tubes for a reason?
 

90sickfox

Wasn't a pretty sight...and I've got big hands
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Leverage... thats why they put them out towards the flange. For every inch of extension theres X amount of additional force. Think long breaker bar instead of stubby ratchet. The dampening of the quad shock would have to increase to get the same result mounted further away. A half inch of movement at the quad shock will multiply to way more movement at the wheel. I'm sure there's a formula for it. If working properly they would help.
 
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joekurt

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Oct 28, 2021
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Kit is a Classic Roadsters Sebring MX. Company has been out of business for quite a while. Chassis is parallel rectangular steel rails 2"x3" cross section 27" wide inside to inside of rails. Drivetrain is Ford 302 (0.030" over), AFR 165 heads, cam aimed at max low end torque, Tremec 5 speed, 3.55 gears through an Eaton Detroit locker and 31 spline axles. The original kit was built in 1989-1991 (red car) and was in a barn fire. Plan was for me and my son to restore it but we found that there was just too much damage to the body from the fire. So, my son found the green kit in Connecticut. Looks like an old Austin Healey roadster. I'll try to attach some pics.
IMG_1966.JPG
IMG_0524.jpeg
 

joekurt

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Oct 28, 2021
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Leverage... thats why they put them out towards the flange. For every inch of extension theres X amount of additional force. Think long breaker bar instead of stubby ratchet. The dampening of the quad shock would have to increase to get the same result mounted further away. A half inch of movement at the quad shock will multiply to way more movement at the wheel. I'm sure there's a formula for it. If working properly they would help.
Thanks 90sickfox! Now we’re getting somewhere. My understanding is that under acceleration the pinion gear tries to “climb” the ring gear causing the rear end to rotate slightly due to the give in the various softer bushings. When it reaches the point where the bushings can’t flex any further the rear snaps back and that’s what causes wheel hop. Now, if one wheel moves more than the opposite wheel ( as in going over bumps in the road), I can understand your point about leverage, but if the whole rear moves in the same direction at the same time, doesn’t that eliminate the issue of leverage? Or in other words, if the whole rear moves slightly forward or backward (or rotates up or down) before it snaps back shouldn’t that motion be transferred equally to both shocks, regardless of where they’re positioned?

Maybe when the rear snaps back it doesn’t do it equally at each wheel?
 

90sickfox

Wasn't a pretty sight...and I've got big hands
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Hmmm....interesting.

The quad shocks do way more than help wheel hop. They are designed to dampen jolts. On a factory car hitting bumps on one side will cause a certain miniscule steering change. The quads help stop that. I've never seen a car wheel hop without loosing traction.

If the load is at the center of the carrier then seems like the quads would help even more towards the center. This may help the deflection dampening but it wouldn't help the movement at the flanges.

If you used aftermarket control arms it would allow you to dial in the pinion angle and help solve all these discussed issues.
 
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Mustang5L5

Put lubricant all over the balls
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FYI, I run max Motorsports control arms, new bilstien shocks and other suspension upgrades , checked my pinion angle and I still had wheel hop. I put the quads back on.
 
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joekurt

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Oct 28, 2021
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Thanks Mustang 5L5. I've seen enough posts from guys that say exactly what you're saying. I suspect it probably has a lot to do with how much power is being pushed through that rear. What HP are you making in your 5.0L?
 

7991LXnSHO

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I’ve seen a 79 4 cylinder Ghia, with a manual transmission and air shocks, wheel hop so bad that it should have broken something. (There were no quad shocks available on 79’s.) The farther jacked up it was, the easier it would wheel hop. The driver thought it was fun, but from the outside it was really violent.
Keeping the LCAs parallel to the ground and chassis seems to help avoid wheel hop.
 

joekurt

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Oct 28, 2021
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Thanks everyone for the help. I've decided to go with the quad shocks. Need one last bit of help. Since I'm putting them in a kit car that has no attachment points on the chassis for those quad shocks I have no idea how far the chassis point should be from the attachment point on the 8.8 rear. Does anyone know offhand how far apart those attachment points are on the Fox body Mustangs?