Loose Control Arm Play = Caster Adjustment

[Some Random Guy]

Control arms are not the same length, so their arcs are already different. This means at some point in their travel they will already bind once the bolt can’t compress the bushing any more. You’re starting out compressed, so at best your up-arc will bind early. More likely, both directions will bind early.
Maybe your shocks will limit travel first, but you’re still going to wear out your bushings faster with un-necessary stress, and potentially lose ride performance in the pursuit of a caster number. It’s just a number, not a magic boost in handling.

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[Kevin32199]

Control arms are not the same length, so their arcs are already different. This means at some point in their travel they will already bind once the bolt can’t compress the bushing any more. You’re starting out compressed, so at best your up-arc will bind early. More likely, both directions will bind early.
Maybe your shocks will limit travel first, but you’re still going to wear out your bushings faster with un-necessary stress, and potentially lose ride performance in the pursuit of a caster number. It’s just a number, not a magic boost in handling.
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Not that I agree with any of that, but regarding your claim of control arm bushing "compression"--I dont see slight compression being what wears out bushings. I'll get to why I dont agree in a moment. First, about the uneven control arm lengths--that does not cause binding--they are designed to rotate the axle to change suspension geometry with movement. What you call binding is actually just pressure the bushings are made to endure--they are holding the axle in place after all, arent' they?. Wear or damage is caused by forces that tear the center out, like extreme articulation. Tightening the bushings when the control arm is in a position it wont be in most of the time will cause constant torsional tension, the bushing will never "relax" and this can cause wear and possibly tear over a much longer time. We dont see people going off road with their control arm bolts loose to save their bushings, so apparently that's not a huge concern. The bushings are also made to be compressed and stretched in torsion with suspension movement. The same goes with slight constant compression. The only way to keep your bushings perfect is to take them all out and store them on a workbench in a climate controlled environment and spray them with rubber conditioner every weekend--which is why I do not agree with your statement regarding compression. Picture the difference in bushing compression between: 1) A control arm bolt on one side of a bolt hole 2) A control arm bolt on the other side of a bolt hole 3) An adjustable control arm set at a longer length. In all three of the above cases, at rest the front axle weight and spring are putting pressure on the bushings. Even if you leave all the bolts loose, there will still be pressure on the bushings. The only difference between all 3 is the relative position of the control arms and axle (in caster, degrees rotation of the axle). The bushings can never have zero compression on them, as they are holding the axle in place, even at rest. If you dont believe me, take your lower control arms out completely and watch your axle rotate--it will definitely find another "relaxed" position. But then what about the upper control arms/bushings? You'll have to take them out too. Then there will be pressure on the driveshaft until you disconnect it. Then the brake lines will strain. Only when the axle is totally disconnected from the vehicle, will there be no more "strain" or "compression" except the pressure on your garage floor where it's laying.

 

[Kevin32199]

Not that I agree with any of that, but regarding your claim of control arm bushing "compression"--I dont see slight compression being what wears out bushings. I'll get to why I dont agree in a moment. First, about the uneven control arm lengths--that does not cause binding--they are designed to rotate the axle to change suspension geometry with movement. What you call binding is actually just pressure the bushings are made to endure--they are holding the axle in place after all, arent' they?. Wear or damage is caused by forces that tear the center out, like extreme articulation. Tightening the bushings when the control arm is in a position it wont be in most of the time will cause constant torsional tension, the bushing will never "relax" and this can cause wear and possibly tear over a much longer time. We dont see people going off road with their control arm bolts loose to save their bushings, so apparently that's not a huge concern. The bushings are also made to be compressed and stretched in torsion with suspension movement. The same goes with slight constant compression. The only way to keep your bushings perfect is to take them all out and store them on a workbench in a climate controlled environment and spray them with rubber conditioner every weekend--which is why I do not agree with your statement regarding compression. Picture the difference in bushing compression between: 1) A control arm bolt on one side of a bolt hole 2) A control arm bolt on the other side of a bolt hole 3) An adjustable control arm set at a longer length. In all three of the above cases, at rest the front axle weight and spring are putting pressure on the bushings. Even if you leave all the bolts loose, there will still be pressure on the bushings. The only difference between all 3 is the relative position of the control arms and axle (in caster, degrees rotation of the axle). The bushings can never have zero compression on them, as they are holding the axle in place, even at rest. If you dont believe me, take your lower control arms out completely and watch your axle rotate--it will definitely find another "relaxed" position. But then what about the upper control arms/bushings? You'll have to take them out too. Then there will be pressure on the driveshaft until you disconnect it. Then the brake lines will strain. Only when the axle is totally disconnected from the vehicle, will there be no more "strain" or "compression" except the pressure on your garage floor where it's laying.

 

[Some Random Guy]

You kind of made my point towards the end. If it was just control arms, you’re right the axle is free to rotate. However, the springs, driveshaft, shocks, etc all play a part in stopping the axle from rotating. Thus, we want to maximize travel with that fixed axle moving along 2 arcs. My bushings limited my travel during instal of my lift with my sway bar and shocks disconnected trying to jam my springs in.
Here is a visual of what I’m trying to say with the bushings:

The arc is exaggerated to demonstrate the point. A fairly neutral bushing would look like something on the left. As the axle moves, if not free to rotate, it will travel until the bolt can’t compress the bushing anymore (bind). If you pre-load with the bushing already forced to one side to adjust your caster, you look more like the right side. The bolt has much less distance before it binds due to compression.
Now, if you have aftermarket bushings this may not be your limit during flex. At that point, I don’t think you have any maintenance concerns. It will wear faster, but you use your vehicle so it is inevitable, which is me rewording part of your statement as I understood it.

 

[Glamisfan]

You’re not preloading or binding anything with this method. You’re simply using the slop in the bolt holes inside the metal sleeve of the bushing and the frame mount to ever so slightly adjust the final resting place that it will be torqued down. I used this method recently to get 1/8” additional wheel well clearance, as well as change my thrust angle to change it from a slight right hand pull to a slight left hand pull. I even took pictures. All right rear links loosened, used a 2” ratchet strap to pull it forward just to see how much it moved, then pulled it backwards, tightened everything, released the strap, and gained 1/8” wheel base on the passenger side. Winning!

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