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CrazyAl -> LCA angle & LCA relocation brackets & you (2/15/2007 10:13:45 PM)
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There's been a lot of questions lately about LCA relocation brackets, so instead of answering the same question ten times I thought I'd explain everything carefully and then leave it here for all to read, and so I can link back to it when it comes up in the future. So here goes:
LCA Angle. There has been a lot of discussion about how adjustable LCAs let you change your pinion angle. But what about LCA relocation brackets? What do they do? LCA brackets attach to your rear axle, at the rearmost end of the LCA. They have multiple different bolt holes that you can choose between, allowing you to choose what the angle of your LCAs is.
The LCA angle is important becasue of what the LCAs do. The main job of the LCA is to transfer the force from your rear axle to the body of the car. They are literally what pushes your car forward when you accelerate. (The UCA contributes too, but to a lesser extent). The LCAs have a pivot at each end. This means that they cannot apply a torque or "twisting" force. They can only apply force in a straight line, along their length. You could not, for example, use an LCA as a wrench. But you could push against something with it.
When an 05+ Mustang rolls out the door at Ford's plant, the car is configured so the LCAs are basically paralell with the ground. They are horizontal. Thus, when the axle starts to push forward, the LCAs push along their length--horizontal--and they push the car straight forward. Makes sense, right?
So what happens if you change this angle? The most common case of this is if the car is lowered. When you lower the car you lower the car's body. But, the rear axle stays put. This has the effect of lowering the front of the LCA. Instead of being horizontal, the LCAs are now lower in the front and higher in the rear. When you accelerate, the LCAs push in a straight line, just as they aways do. But now the straight line is angled downwards at the body connection of the LCA. This means that MOST of the force from the wheels is still pointing forward, but a portion of it is actively pushing the body of the car down towards the ground. Newton taught us that every action has an equal an opposite reaction. And it's this reaction that's bad. The reaction to the body being pressed down, is that the rear axle is being pressed UP. This force actively lifts the tires off the pavement....as if you had a big helium balloon tied to your axle. The harder you accelerate, the more your axle gets lifted up...and that costs you traction. A car that is lowered without LCA relocation brackets has LESS traction under acceleration than a stock-height car becasue of this! The angled LCA also causes a rougher ride.
How can we fix that? LCA relocation brackets let you change the position of the rearmost end of the LCA. By switching them to a lower mounting postion, we can restore the OEM horizontal configuration on a lowered car. That means you can have your car lowered, but without suffering the ill effects I just described.
But we can also change things to our advantage. If we lower the rear end of the LCA even more, so now it's lower in the rear than at the front, we get a similar situaton to what I described above...but backwards. Now, the force from the rear axle is pushing up on the body. The reaction force pushes DOWN on the axle, planting it to the pavement. In this case the harder you accelerate, the more the tires are pressed onto the road...providing more traction. This is excellent for drag racing, and this kind of adjustment is key on all successful drag race vehicles. This is why all serious drag race cars run a multi-link rear suspension or ladder bars (if the rules allow it), becasue it enables better traction at launch.
Thus, using LCA relocation brackets lets you correct your LCA angle if you lower the car. They also give you the option of running an even more agressive setting (lowered or not) which will enhance your traction at launch.
Note that running the LCA at an angle (any angle, good or bad) will result in slightly ride harshness on rough roads.
[image]local://upfiles/32957/5B289EA99F124F12824DCA41EA02DF69.jpg[/image]
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