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Discussion Starter #1 (Edited)
Removal of upper control arm for roadracing

I am hearing from a few people that removing one upper control arm in the rear ( when running a panhard) is the way to go for racing. Any views on this ? Also what about ditching the quads ?
 

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Discussion Starter #3
I am installing a Kenny Brown Trackit. I already have a new thicker panhard bar. (The one with the kit was really cheesy looking) And as far as ditching the quads, guys are telling me that they do more harm than good for the turny stuff because they bind up the rear suspension.
 

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Discussion Starter #5
I only paid $200 for it and it was never used. I did not have the chance to mock it up to the car yet. They say there is a newer designd one (from Kenny Brown) that does not have the same problem you have stated with the trunk ripping. I am not sure if this is the newer one or older one. But just in case I have big plates I am welding to the car at the weakest attachment points.

Thank you for your input.
 

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This is a well known setup, commonly called the “poor man’s 3 link.” My advice is not to run it.

If you’re on a tight budget, consider the upgrades that can make big improvements to the suspension within the constraints of the stock geometry. If you want to go all out, compare the competition setups, like the Steeda 5-Link or one of the Torque Arm kits. But skip the poor man’s three link.
 

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Discussion Starter #8
Thanks guys. I will put the gained info to good use.
 

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techguy said:
This is a well known setup, commonly called the “poor man’s 3 link.” My advice is not to run it.

If you’re on a tight budget, consider the upgrades that can make big improvements to the suspension within the constraints of the stock geometry. If you want to go all out, compare the competition setups, like the Steeda 5-Link or one of the Torque Arm kits. But skip the poor man’s three link.

Why not run the “poor man’s 3 link.”
Is it bad for the car?
Does it not work?
I would like to hear technical reasons why not to do it.
 

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The main problem is that the PM3 is not a properly designed three link, just a 4 link with one of the arms cut off. Now if the upper arm was straitened out and the geometry fixed, it could be a very good system. But as it is it is a mess.

A) The forces on the 1 remaining upper arm are increased to the extreme. The angle of the arm makes it very inefficient in resisting axle rotation. This results in three problems:
1) Reduction in rotational control of the axle, i.e. reduction of traction and pinion angle control.
2) Overstress of the control arm and bushings, primarily resulting in shortened bushing life, which aggravates problem number 1.
3) Overstress of the control arm attachment point on the chassis, resulting in broken spot welds and torn sheet metal if not properly reinforced.

B) The resultant force vector from having only 1 angled upper arm pushes and pulls the axle sideways in response to braking or acceleration. The movement will be limited by the panhard bar. But even so, it can produce unwanted and unpredictable motion of the axle, depending on the amount of compliance in the bushings and the height of the panhard bar.

C) The remaining upper control arm still exerts limited lateral control on the location of the axle, creating a conflict with the panhard bar. If this conflict is solved with soft bushings, pinion angle control suffers. If spherical bearings are used all around, the axle will twist (yaw) as it is pulled in different directions by the panhard bar and upper arm.

D) The parts of the suspension that control forward traction and braking have not been improved. They remain limited by the same factors that limit the factory suspension, but with the added handicap of poorer pinion angle control as outlined in (A).

The above was written off the top of my head in about 5 minutes. There is more to be discussed, both pro and con.

The short answer is that it is a solution to a problem that creates more new problems than it solves. I recommend that if you are going to run a panhard bar, go all the way and do it right with a completely designed suspension system. If you are not prepared to go all the way all at once, then leave off the panhard bar and make improvements to the existing configuration. It has its flaws, but there are still big improvements that can be made. I’ve seen plenty of well sorted out “factory” style suspensions run circles around cars with “trick” parts that weren’t sorted out.
 

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Thanks,
I guess every car is different. My MM PHB with MM LCA works grate.
I will save to get the MM TA and do it right. I thought about going with the PM3L till I saved up enough. Because of the reasons you listed I will keep what works for now.

Thanks again
 
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