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Old 12-27-2021, 05:05 AM
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Question Lifted rear control arms A-body ?

I just watched this video , https://www.youtube.com/watch?v=fv0y8SNcFc8 from Vanguard motor.

And @ 6:50 he points out the lifted rear control arms.
I've never seen this before , anybody know what that's for exactly ?

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Old 12-27-2021, 09:05 AM
66sprint6 66sprint6 is online now
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I believe to mitigate wheel hop.
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Old 12-27-2021, 11:21 AM
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Yep, "no-hop bars", at one time it was common to install that setup to try and get better traction. Now, selecting better springs and shocks seem to get better results.

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Old 12-27-2021, 12:35 PM
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My old Buick GS NMCA running buddy had them on his GS.

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Old 12-27-2021, 03:44 PM
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They change the instant center, and plant the tires harder.

H-O Racing made them for a long time, now I think QA1 is the go-to for them.

https://www.qa1.net/automotive/suspe.../anti-hop-bars

Dick Miller made them too, and wrote about them in his book:

https://www.amazon.com/How-Hook-Laun.../dp/B08FNX6MQB

(I do not support Dick Miller by the way)

There are drawbacks, there is a negative impact on handling when using them. I forget the specifics, but sure others can chime in. I think it makes a car get loose on corner exits, but would have to revisit it to be sure.

.

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Old 12-27-2021, 06:09 PM
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Quote:
Originally Posted by HWYSTR455 View Post
They change the instant center, and plant the tires harder.

H-O Racing made them for a long time, now I think QA1 is the go-to for them.

https://www.qa1.net/automotive/suspe.../anti-hop-bars

Dick Miller made them too, and wrote about them in his book:

https://www.amazon.com/How-Hook-Laun.../dp/B08FNX6MQB

(I do not support Dick Miller by the way)

There are drawbacks, there is a negative impact on handling when using them. I forget the specifics, but sure others can chime in. I think it makes a car get loose on corner exits, but would have to revisit it to be sure.

.
It changes the lever arm action on the upper control arms. The converging 4 link design inherently has bind in the system which is why you never use solid bushings in them.

By increasing the height of the attachment points, you increase the force exerted on the top of axle. The converging nature of the upper control arms push the axle into the ground. When that force is being applied equally, it really works in your favor to plant the tires and reduce axle wrap.

The problem becomes when the force is applied unequally, like when you are powering out of the apex of a corner. The application of force overwhelms one side of the axle and twists it into the opposing force of the opposite side of the suspension. When rubber bushings are used, this creates a cushion to absorb the movement in a linear and controllable way. But, once the bushing has no more tolerance to take up, the system will bind and unload the tires, resulting in an instant and near uncorrectable oversteer.

You don't hear about it as much with A bodies, because generally the types of tires being used and the kind of driving activity being done doesn't put the car near that limit. You hear about it a lot with Fox through SN95 chassis mustangs.

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Old 12-27-2021, 07:54 PM
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I fabbed a set out of aluminum for my 66 442. It stopped the burnout bouncing cold. Supposedly the 68-72's had better instant center geometry that this was not as much of an issue.

JLM: is that why Fox's have quad shocks?

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Old 12-27-2021, 08:18 PM
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Originally Posted by Scarebird View Post
I fabbed a set out of aluminum for my 66 442. It stopped the burnout bouncing cold. Supposedly the 68-72's had better instant center geometry that this was not as much of an issue.

JLM: is that why Fox's have quad shocks?
I am not well versed in the Fox chassis. It’s my understanding that the quad shock is there to dampen oscillation in the axle.

Rear suspension packaging in the Fox has to be pretty awkward considering the size and wheelbase of the car. If I had to make a guess the upper links likely converge at a pretty steep angle, necessitating overly soft bushings. Soft enough to allow some significant movement of the package.

All I know for sure is that people that remove them tend to complain about excessive wheel hop after removal.

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Old 12-28-2021, 08:31 AM
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Quote:
Originally Posted by JLMounce View Post
It changes the lever arm action on the upper control arms. The converging 4 link design inherently has bind in the system which is why you never use solid bushings in them.

By increasing the height of the attachment points, you increase the force exerted on the top of axle. The converging nature of the upper control arms push the axle into the ground. When that force is being applied equally, it really works in your favor to plant the tires and reduce axle wrap.

The problem becomes when the force is applied unequally, like when you are powering out of the apex of a corner. The application of force overwhelms one side of the axle and twists it into the opposing force of the opposite side of the suspension. When rubber bushings are used, this creates a cushion to absorb the movement in a linear and controllable way. But, once the bushing has no more tolerance to take up, the system will bind and unload the tires, resulting in an instant and near uncorrectable oversteer.

You don't hear about it as much with A bodies, because generally the types of tires being used and the kind of driving activity being done doesn't put the car near that limit. You hear about it a lot with Fox through SN95 chassis mustangs.

The bind issue has been resolved with several different types of joints offered by a couple aftermarket vendors, so you can, and should, run this type of solid bushings system in the rear.

Part 1: https://www.youtube.com/watch?v=hPO-G5wLD54

Psrt 2: https://www.youtube.com/watch?v=aDR5y4hsdik

Part 3: https://www.youtube.com/watch?v=u0IvDkMV_q8

Mark at SC&C also has a solution. His book is a great reference regarding GM 4-link suspensions.

https://www.amazon.com/How-Make-Your.../dp/B08FNKF94Q

.

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Last edited by HWYSTR455; 12-28-2021 at 08:39 AM.
  #10  
Old 12-28-2021, 11:39 AM
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Yeah Heim's, rotos and johnny joints work great in those. I'd run the roto joints in a street car for NVH concerns.

I should have been specific that you don't run traditional solid bushings in a converging 4 link setup. the arms have to be able to articulate.

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  #11  
Old 12-28-2021, 12:44 PM
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Used these forever, 67 GTO, four speed, Ram Air4 engine! Air bags, 12 psi right side, 4 psi left side and no hop bars! Removed the bars when changed over to TH400 as they weren't needed anymore. The bars plant the tires with a 4 speed car and it stays straight banging gears.
The no hop bars are a keeper!!

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Old 12-30-2021, 06:13 AM
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Quote:
Originally Posted by JLMounce View Post
You don't hear about it as much with A bodies, because generally the types of tires being used and the kind of driving activity being done doesn't put the car near that limit.
What does that mean exactly ? . . . that A-body's are driven mostly by elderly people ?

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Old 12-30-2021, 03:09 PM
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Quote:
Originally Posted by Bob Timmermans View Post
What does that mean exactly ? . . . that A-body's are driven mostly by elderly people ?
Lol, no. More that they are typically driven in a straight line.

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Old 01-01-2022, 02:43 PM
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I've run them on my Chevelle for more than 20 years, and dad has had them on his GTO even longer.

As said, they change the bar angle for an instant center closer to the rear of the car, which in turn plants the tires. More instant center hits the tires harder, which is what you want with a drag radial, not so much with a slick.

We use them in conjunction with adjustable upper control arms to dial in the pinion angle, and a couple air bags to set some preload, and adjustable shocks.

With this simple setup dad's went a 1.46-1.48 60 foot times with a soft leave on a 275 drag radial with more left. My Chevelle goes in the upper 1.50's consistently.

These are just street cars we play with at the track. Street driving is what these cars see 95% of the time and I can't even tell they are back there. The cars don't exhibit any funny business even on the mountain roads we drive. However we aren't going for lap times so......

On my sons fox we've left the quad shocks in place. Many fox owners remove them but I found axle hop really becomes an issue so they stay on the car. They make all the same no hop bars, lower relocation brackets, adjustable arms etc....that are made for the older A-bodies. In fact the aftermarket support for the fox platform is flooded with excellent suspension pieces. They are probably one of the best platforms for drag racing and have always been popular for decades. They are basically the same 4 link coil spring style suspension as an A-body.

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