Drop Spindles - PST vs. Magnum Force vs. Fatman vs. ?
Even the 1.03" bars allow for a decent drop. Obviously there are limits, if you drop the car more than you've reduced the necessary travel you'll bottom out. But think about the spring rate change- the stock bars have a wheel rate of ~100 lb/in. The 1.03" bars, although PST doesn't advertise the rate, should have a wheel rate that's close to 220 lb/in, give or take 5 lb/in or so. That means you've more than doubled the wheel rate. And you'll need less than half the travel the stock bars needed. There's only about 4" of travel in the original suspension. So, with a 200 lb force input with the original suspension, you're talking about 2" of travel. On the 1.03" bars, you're talking about less than 1". With a 300 lb input the stock bars are at 3" of travel (and have hit the bump stops because there isn't 3" in one direction), where the 1.03" bars are only at 1.4" of travel. It's a dramatic change.
But you ABSOLUTELY need a re-alignment if you lower the car. The suspension geometry changes as the car is lowered. Camber, caster, and toe all change as the car is lowered. If you really slam the car in the weeds, you may need offset UCA bushings to get the alignment specs back to where they need to be. But you probably don't want to lower that much with the 1.03" bars. My cars sit pretty low, but I also have 1.12" bars, so, over triple the rate of the original bars.
This isn't accurate. The lower ball joint mounts are in exactly the same place as stock. Exactly. The difference in the appearance of the mount is because the axle stub has been moved up 2" on the face of the spindle. Because of this, Magnumforce removed material between the ball joint mounting holes because it's not necessary for the strength of the face of the spindle anymore. So, it appears that the lower ball joint mount has moved.
But, the tie rod end doesn't move, the axle stub does. That still puts an additional 2" between the center of the wheel and the tie rod end, which changes the bump steer. If you lower the car a full 2", then the tie rod angle remains the same. But, if you don't lower the car the full 2", you increase the angle on the control arms and tie rods, which tends to add more bump steer as well.
It's not a horrific change in geometry, like I said earlier most drivers using their cars in normal street driving situations probably wouldn't notice it. But, that also doesn't mean it isn't there. The big difference isn't between a stock ride height car and one that's been lowered 2" with the drop spindles because the angle of the control arms and tie rods stays the same in that situation. So the roll center remains the same, and the car still benefits from a lower CG. The difference really takes shape though when you compare a car lowered 2" with drop spindles and one that's been lowered with the torsion bar adjusters. The car lowered 2" with drop spindles maintains the stock control arm and tie rod angles, where the car lowered with the adjusters now has control arms and tie rods that are basically parallel to the ground, improving the instant roll center, camber curve, and even improving the amount of bump steer vs stock.
This is a pretty simple diagram and not truly to scale, but it illustrates the angle changes I'm talking about
Even the 1.03" bars allow for a decent drop. Obviously there are limits, if you drop the car more than you've reduced the necessary travel you'll bottom out. But think about the spring rate change- the stock bars have a wheel rate of ~100 lb/in. The 1.03" bars, although PST doesn't advertise the rate, should have a wheel rate that's close to 220 lb/in, give or take 5 lb/in or so. That means you've more than doubled the wheel rate. And you'll need less than half the travel the stock bars needed. There's only about 4" of travel in the original suspension. So, with a 200 lb force input with the original suspension, you're talking about 2" of travel. On the 1.03" bars, you're talking about less than 1". With a 300 lb input the stock bars are at 3" of travel (and have hit the bump stops because there isn't 3" in one direction), where the 1.03" bars are only at 1.4" of travel. It's a dramatic change.
But you ABSOLUTELY need a re-alignment if you lower the car. The suspension geometry changes as the car is lowered. Camber, caster, and toe all change as the car is lowered. If you really slam the car in the weeds, you may need offset UCA bushings to get the alignment specs back to where they need to be. But you probably don't want to lower that much with the 1.03" bars. My cars sit pretty low, but I also have 1.12" bars, so, over triple the rate of the original bars.
This isn't accurate. The lower ball joint mounts are in exactly the same place as stock. Exactly. The difference in the appearance of the mount is because the axle stub has been moved up 2" on the face of the spindle. Because of this, Magnumforce removed material between the ball joint mounting holes because it's not necessary for the strength of the face of the spindle anymore. So, it appears that the lower ball joint mount has moved.
But, the tie rod end doesn't move, the axle stub does. That still puts an additional 2" between the center of the wheel and the tie rod end, which changes the bump steer. If you lower the car a full 2", then the tie rod angle remains the same. But, if you don't lower the car the full 2", you increase the angle on the control arms and tie rods, which tends to add more bump steer as well.
It's not a horrific change in geometry, like I said earlier most drivers using their cars in normal street driving situations probably wouldn't notice it. But, that also doesn't mean it isn't there. The big difference isn't between a stock ride height car and one that's been lowered 2" with the drop spindles because the angle of the control arms and tie rods stays the same in that situation. So the roll center remains the same, and the car still benefits from a lower CG. The difference really takes shape though when you compare a car lowered 2" with drop spindles and one that's been lowered with the torsion bar adjusters. The car lowered 2" with drop spindles maintains the stock control arm and tie rod angles, where the car lowered with the adjusters now has control arms and tie rods that are basically parallel to the ground, improving the instant roll center, camber curve, and even improving the amount of bump steer vs stock.
This is a pretty simple diagram and not truly to scale, but it illustrates the angle changes I'm talking about
