Need some help/advice on setting rear ride height and spring plate angle

[cabmandone]

I just finished replacing my spring plate bushings. I used an angle finder for each side with the control arms and shocks disconnected from the spring plates. I installed the spring plates at the exact same angle as they came off (about 31 degrees). When I took the car off the lift, the back was significantly higher than it was prior to replacing the bushings. I thought this might be due to the new bushings?? I bounced the back of the car to get things settled into place but it was still higher than I wanted and outside the range of the adjuster.

I readjusted the spring plate angle to lower the car, because it was high enough that the adjustable spring plates wouldn't have lowered it enough. I set the spring plate angle at 29 degrees which from my reading should have lowered the car by about 3/4". When I set the car down on all four it was significantly lower, I went from being able to put three fingers between the wheel well and the top of the tire to not being able to fit one finger between.

I measured from the ground to the center of the torsion bar cap on the spring plate. For some reason, my driver's side is about 1/2" higher than the passenger side. I have stock torsion bars and all stock suspension. What am I doing wrong?

[Jonny042]

Sounds like you're getting inconsistent slip/grip on each side since the bushings are the only change you made.

Did you glue the bushings to the tube? Use a large amount of lube on the outers?

For reference, 1 degree on the spring plate starting position should get you about 7mm ride height change (EDIT - note this chart is useless to you for choosing a starting angle but the height difference should be similar, and the ride heights will apply as well):

[BK911]

Never been a fan of using angles.
I use a measuring tape.
Measure fender heights.
Set rear of car on jack stands at torsion tube.
Disconnect SP from trailing arm.
Measure ground to end of SP.
Set ASP to center of its range.
Re index SP until change in height of SP is 1/2 the change of height desired at fender.
Put back together.
Remeasure.
Fine tune with ASP.
Drink lots of beer.

[cabmandone]

Originally Posted by Jonny042

Did you glue the bushings to the tube? Use a large amount of lube on the outers?

Prepped the spring plates by sandblasting and coating. No coating on the surface the bushings ride on. I wanted to keep the blast profile thinking this would increase surface area for adhesive and improve bond. I used super glue that was slow set, fast cure and twisted while installing the bushings. For lube when installing the spring plates, I just used dish soap. From the threads I've read, there are two schools of thought on the spring plate bushings and to grease or not.

[cabmandone]

Originally Posted by BK911

Drink lots of beer.

I've got that part covered! This bothered me so much last night that I woke up at 3 a.m this morning and couldn't stop thinking about why my ride height was too high. So I started reading about settings at 3 a.m. I thought I had it figured out so I went out to my shop at 7:30 and readjusted the angles. Turns out I didn't have it figured out!

[Jonny042]

So where are you at now?

My next question is going to be about lower shock mount and sway bar bolts. If you loosen them do things start to make more sense?

[Tremelune]

Just to check...Are you rolling the car backwards/forwards a few feet after lowering it back down each time? These long-ass trailing arms stay rather hunched, and bouncing the car won't move the tires out to their neutral position.

[Zuffenwerker]

Originally Posted by Tremelune

Just to check...Are you rolling the car backwards/forwards a few feet after lowering it back down each time? These long-ass trailing arms stay rather hunched, and bouncing the car won't move the tires out to their neutral position.

I second this and take it one further you need to go drive the car before you measure the height after having it apart. Go do some hard lefts and rights hit some RR tracks get it settled then measure

Daniel

[cabmandone]

I'm going to go out this morning and take another swing at it. I plan to go about half way between where my angle started and where it is now. I'm going to take it out and drive it once I'm done and then check the measurements.

[Michael7810]

Just a thought are you measuring the SP relative to the door sill angle? I just replaced my SP bushings and set the angle at 34* relative to the door sills according to the Bentley manual. (e.g. My door sills are about 2* nose down so I set the absolute angle of the SP at 32*.). I have not put my car on the ground yet as I'm doing other work plus I can't get the damn control arms back in because the new split bushings are too wide. I'm going to work on that today. Good luck

[wjdunham]

Originally Posted by Michael7810

Just a thought are you measuring the SP relative to the door sill angle? I just replaced my SP bushings and set the angle at 34* relative to the door sills according to the Bentley manual. (e.g. My door sills are about 2* nose down so I set the absolute angle of the SP at 32*.). I have not put my car on the ground yet as I'm doing other work plus I can't get the damn control arms back in because the new split bushings are too wide. I'm going to work on that today. Good luck

Don't want to derail this thread, I sent you a PM on the split-bushing too wide issue. I'm about to replace mine and am having nightmares about getting them back into the receivers...
Bill

[cabmandone]

I got it! Turns out when I installed the bushings the first time they were tighter than each subsequent attempt. Had I taken the car out and driven it, as others suggested, it probably would have dropped into its original height. Each time I removed, soaped, and reinstalled, I think it loosened up a bit. I'm now back at the original 32 degrees and I'm well within range of the spring plate adjusters to bring the rear to exactly where I want it to be. I'm aiming for 25-25 1/2 inches from ground to wheel well. Had I gone 34-35 degrees as the manuals suggest, I'd have probably ended up right where I want to be. The plus side? I know it only takes about 2 hours, start to finish, to adjust the spring plate angle if I want to tackle this job ever again... which I do not.

[cabmandone]

Got everything level in the back at 25 1/2” to the wheel well which is where I want it so I don’t have tire rub. This measurement was achieved after a drive going over bumps and RR tracks. I made an adjustment to the front to level it out, went for a drive, measure again and my right rear is at 25 1/8 while the drivers side stayed put at 25 1/2. I don’t get why it settled but it did so I’m going to drop the drivers side down to 25 1/8 to match the passenger side.

[proporsche]

i always do drivers rear side 5mm higher

[cabmandone]

Ya know, this stuff'l drive ya nuts if ya let it. I'm getting it aligned tomorrow and calling it good enough. I dropped the drivers side down a bit and it's within 1/2 inch.

[Tremelune]

The height should not be the same at all four corners...The front will be slightly higher due to the shape of the fenders. When you get it right you tend to wind up with a slight rake toward the front. Really, you should be measuring from the center of the torsion bars and wheels, but it's a pain in the ass and nobody seems to bother.

After an alignment, you'll want to get a corner balance, and this can affect the ride heights a little bit anyway. Better to have the corners balanced than the ride heights closer.

[cabmandone]

Originally Posted by Tremelune

The height should not be the same at all four corners...The front will be slightly higher due to the shape of the fenders. When you get it right you tend to wind up with a slight rake toward the front. Really, you should be measuring from the center of the torsion bars and wheels, but it's a pain in the ass and nobody seems to bother.

After an alignment, you'll want to get a corner balance, and this can affect the ride heights a little bit anyway. Better to have the corners balanced than the ride heights closer.

There are members here that run all four corners the same. As long as you like the look and you're not tracking the car, I guess it all becomes personal preference. I put my front about 26" settled. The back is at 25-1/8" settled.

As far as corner balance goes, I don't track the car so unless I notice some ill handling on the roads I drive, I'm not going to mess with it. I prefer the balanced look of both sides being equal. My brother's car is corner balanced and there is visible difference in the left and right rear. I can't stand that. I'm a gap freak.

[rowingone]

so this is why I didn't get things right the last time . . the rear is too low. I disconnected the spring plate . .measured 28.4 degrees before I disconnected it . . now its loose and it measures 35 . .what am I doing wrong? If the spring plate is just hanging and not attached to the suspension shouldn't the angle be the same?