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Old 11-27-2012, 10:54 PM   #31
mulletman
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Quote:
Originally Posted by MattAvino View Post
With 4 degrees of camber correction, I'm concerned I might end up with positive camber when running with H&R races. It will probably end up being the perfect combo but I might as well inquire anyways.
I'm still somewhat skeptical of the 4 degree figure... as according to the chart above, that would require the angle of the trailing arms to be changed by 15 degrees or so, or maybe I don't know enough about it... I plan on running the H&R as well, and I would be very happy with about 2 degrees of correction or so.

Again, not shitting on the product, I just would be interested to see figures from multiple installers. I still plan on buying the product, and hopefully I can get some numbers eventually!

Last edited by mulletman; 11-27-2012 at 11:13 PM.
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Old 11-28-2012, 06:50 AM   #32
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Originally Posted by ForcedFirebird View Post
It's not the same as lifting/lowering the car, the springs are a pivot and with any fulcrum, the in/decrease is multiplied by the difference in lengths from the center.

As far as the ix bushings raising the subframe, you have it backwards. We just restored an ix rear section, the bushings actually drop the subframe to correct the camber since the ix has a higher ride height than a RWD e30. Some ix guys actually use RWD e30 bushings for their lowered car, but the difference between ix and RWD bushings is no where near 12mm.
I know the springs are a pivot point in this scenario, but they have nothing to do with the angle of the trailing arms. The only thing that matters is the angle of the trailing arms between the wheels and the subframe. Raising the subframe, whether by raising the car or the subframe itself, is the only way to adjust the camber, and both ways get you the same result.

If these bushings bent the center of the subframe up or twisted the top of the subframe towards the front of the car it would be different, but they don't- they only raise it.


And I guess I was wrong about the ix, but that brings me to a different idea. If the ix bushings drop the subframe, then the diff drops along with it since there is no way to raise the diff in relation to the subframe. Ix diffs swap into regular e30's without spacers, so are the spacers in this scenario really necessary? I guess dropping it would give the driveshaft more angle, whereas raising it would give less. Do the ix's have offset diff bushings stock? This is off topic though so I'll stop now.
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Old 11-28-2012, 07:55 AM   #33
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Quote:
Originally Posted by MattAvino View Post
With 4 degrees of camber correction, I'm concerned I might end up with positive camber when running with H&R races. It will probably end up being the perfect combo but I might as well inquire anyways.
The only way you might end up with positive camber is with stock springs.
The change on H&R race springs wont be as extreme, The 4* change was on an extremely lowered car.
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Old 11-28-2012, 01:31 PM   #34
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Originally Posted by silence View Post
The only way you might end up with positive camber is with stock springs.
The change on H&R race springs wont be as extreme, The 4* change was on an extremely lowered car.
oh i see. So the rate of change is exponential.
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Old 11-28-2012, 01:46 PM   #35
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Originally Posted by silence View Post
The only way you might end up with positive camber is with stock springs.
The change on H&R race springs wont be as extreme, The 4* change was on an extremely lowered car.
So with a H&R cup kit (race springs) would there be a benefit to the offset bushings? I would be running the uhmw rtabs too. I DD my car so I dont want to eat tires.

Anyone in Chicago with these bushings that would be willing to take me for a ride?
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Old 11-28-2012, 02:11 PM   #36
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Originally Posted by E30SPDFRK View Post
I know the springs are a pivot point in this scenario, but they have nothing to do with the angle of the trailing arms. The only thing that matters is the angle of the trailing arms between the wheels and the subframe. Raising the subframe, whether by raising the car or the subframe itself, is the only way to adjust the camber, and both ways get you the same result.

If these bushings bent the center of the subframe up or twisted the top of the subframe towards the front of the car it would be different, but they don't- they only raise it.


And I guess I was wrong about the ix, but that brings me to a different idea. If the ix bushings drop the subframe, then the diff drops along with it since there is no way to raise the diff in relation to the subframe. Ix diffs swap into regular e30's without spacers, so are the spacers in this scenario really necessary? I guess dropping it would give the driveshaft more angle, whereas raising it would give less. Do the ix's have offset diff bushings stock? This is off topic though so I'll stop now.

The ix is totally different, it has a one piece drive-shaft. You still need the spacers for RWD, or you will pre-maturely wear your u-joints.

The whole change in camber is affected differently than thinking of it as a see-saw. The TAB's are not square to the car, the reason toe and camber are affected when lowering. Raising the subframe is not the same as raising the car as a whole. It's the same as using a weld in kit and adjusting them as far up as they can go (IE's, not the e30tech ones). The camber is far more effected when raising the sub-frame in relation to the upper spring pad - than effected by picking up the car.

EDIT: Raising/lowering the car is simply compressing/expanding the springs. When you change the pivot point where the trailing arm is attached and leave the upper spring perches in the same position, you are exponentially changing the camber.
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Old 11-28-2012, 09:10 PM   #37
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You're the one talking about a seesaw, not me. And offset subframe bushings are absolutely nothing like the weld in kits that they sell.

I'll put it this way: take the car completely out of the picture for a moment and put the subframe on 2 parallel tubes sticking perpendicularly out of the ground. Now set the subframe 4" off the ground. The trailing arms will be at A angle at this height. Now raise the subframe to 4.5" off the ground. The trailing arms are now at B angle.

It doesn't matter how we raised the subframe that .5", but B will be the same as long as we started at A. Do you understand what I'm saying yet?
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Old 11-29-2012, 07:13 AM   #38
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It doesn't matter how we raised the subframe that .5", but B will be the same as long as we started at A. Do you understand what I'm saying yet?
It's still not the same. When you lift the whole car, the upper spring perch goes with it. When you change the pivot only and leave the spring perch in place, you are changing the the trailing arm's relationship to the body of the car. Since the spring is not at the center of the wheel and is inboard of the trailing arm, raising the sub-frame is like making your springs longer without lifting the car. Do the math. Raising your sub-frame is like lifting the car almost an inch.

I will draw it in CAD to give you a visual.
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Old 11-29-2012, 07:29 AM   #39
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Take spring compression out of the equation. The red rectangle represents the spring in stock config OR with the 12mm raised bushings. The blue rectangle represents the spring when raising the entire car. The red circle represents the 12mm rise in either by lifting the body, or raising the pivot 12mm. The red line represents where the center of the wheel will be in relation to the body with the pivot moved. The blue line represents raising the entire body up 12mm. The green line represents stock TAB location to center of wheel.

When lifting the entire car 12mm, it's not the same as lifting the pivots because in relation to the body - the spring is not at the apex of the triangle. This is simple geometry. Drawing is in scale and can send you a file if you like to see for yourself. When you lift the entire car, you are simply decompressing the spring and allowing that pivot to move down the wheel, yes, but when you triangulate the spring into the equation, it becomes a lever and the results are amplified.
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Old 11-29-2012, 07:41 AM   #40
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You forgot the fact that when you raise the body of the car 12mm, the spring is now taller too. In your picture the taller spring is magically floating above the trailing arm.

The spring is only a pivot point for the initial raise of the subframe, after that it has nothing to do with the angle except for controlling the amount it changes during compression. The pivot is at the subframe at all times while the car is driving.
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Old 11-29-2012, 07:52 AM   #41
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Originally Posted by ForcedFirebird View Post
Take spring compression out of the equation. The red rectangle represents the spring in stock config OR with the 12mm raised bushings. The blue rectangle represents the spring when raising the entire car. The red circle represents the 12mm rise in either by lifting the body, or raising the pivot 12mm. The red line represents where the center of the wheel will be in relation to the body with the pivot moved. The blue line represents raising the entire body up 12mm. The green line represents stock TAB location to center of wheel.

When lifting the entire car 12mm, it's not the same as lifting the pivots because in relation to the body - the spring is not at the apex of the triangle. This is simple geometry. Drawing is in scale and can send you a file if you like to see for yourself. When you lift the entire car, you are simply decompressing the spring and allowing that pivot to move down the wheel, yes, but when you triangulate the spring into the equation, it becomes a lever and the results are amplified.


All of you lines should share one point at the wheel.... unless you lifted your wheel bearings too..



The spring has absolutely no effect on the trailing arm angle, it just supports it. This is simple lever stuff here. If you measure at the subframe for height change everything byron is saying is right.
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Old 11-29-2012, 07:53 AM   #42
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You forgot the fact that when you raise the body of the car 12mm, the spring is now taller too. In your picture the taller spring is magically floating above the trailing arm.

The spring is only a pivot point for the initial raise of the subframe, after that it has nothing to do with the angle except for controlling the amount it changes during compression. The pivot is at the subframe at all times while the car is driving.
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Originally Posted by ForcedFirebird View Post
Take spring compression out of the equation.
Read the text . When you are using the same springs before and after the sub-frame rise, the spring compression dynamics are moot. You will obviously never get the fact that the camber will change exponentially when the spring pad to pivot height is changed.

I'm sure the argument will help someone else. I have machining and engineering experience and the math states the facs that I have presented. I also personally measured the cars well have both welded in kits, and now with raising the sub-frame. The facts and measurements are presented for those who understand.

Also, this is not new-school technology, do some research on the e30 DTM cars, and you will see this was common procedure to extend tire life.
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Old 11-29-2012, 07:55 AM   #43
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All of you lines should share one point at the wheel.... unless you lifted your wheel bearings too..



The spring has absolutely no effect on the trailing arm angle, it just supports it. This is simple lever stuff here. If you measure at the subframe for height change everything byron is saying is right.
He's not understanding it is a lever with the fulcrum at the spring perch.

I will do the math and present another drawing with the wheel center remaining the same before and after the sub-frame rise if you like. You will see it's not like picking the car up 12mm...
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Old 11-29-2012, 07:57 AM   #44
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I hope the argument will help someone else, because it's obviously not helping you. I'm done here.
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Old 11-29-2012, 08:04 AM   #45
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He's not understanding it is a lever with the fulcrum at the spring perch.

I will do the math and present another drawing with the wheel center remaining the same before and after the sub-frame rise if you like. You will see it's not like picking the car up 12mm...
Who cares about the fulcrum at the spring perch... we're talking about measuring from each end... Its not like he said crank your coil adjuster up precisely 12mm and see what happens, everything has been referenced by the height of the body and comparing it to the subframe.


Try your drawing again. The wheel is a fixed point, the only variable is the subframe height. Its actually exactly like picking the car up 12mm.
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