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H&R drop springs installed (COVID-19 quarantine project)

4K views 41 replies 5 participants last post by  AAIIIC 
#1 ·
H&R springs, KYB struts and upper front strut mounts installed

A few things to mention

- The bottom of the front H&R spring did not fit into the strut perch.
-The inner dia. of the spring was too small of the strut perch.
  • I cut one coil of the bottom so it could sit into the strut perfectly.
  • The diameter of replacement KYB strut for the rear was way small than original. I kept my original rear struts and just installed the H&R in the rear
  • I had forgot to remove the front bump stop, so the initial test drive after the installation was not good. No suspension travel in the front
  • Came back and removed the bump stops and that’s where I ended the day
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#3 ·
Back to the drawing board. With the front bump stops removed, now the front struts are bottoming out. Some keys points

  • Unloaded empty strut measure 25.50”
  • Maximum compression stroke of the strut rod measure 5.25”
  • I push the rod into the strut (took a good amount of force) to compress and measure
  • Loaded strut assembly measures 25.50”
  • Due to the shorter spring height, I did not have to compress the H&R spring to install/remove.
  • With the strut assembly installed, jack stand under frame and floor jack under lower control arm. I got 5” of compression before weight of chassis lifted of jack stand
  • So that confirms why the strut it bottoming out. It only has 1/2” travel, no bueno
 
#4 ·
It’s a common fact. When lowering some vehicles with coil springs, it’s ideal to use drop shocks/struts with lowering coils.

The length of the OEM shock/strut is not designed for shorter springs.

I think I figured out a way to make our OEM strut a drop strut. I need to take one more measurement to check my hypothesis 😁

And it involves this
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Laying in bed quarantine style got my wheels turning. So I’m curious how this is going to end 😁
 
#5 ·
If the drop spring is causing the strut to bottom out. Meaning the strut has compressed almost completely at right height. Which is a common problem with short compression OEM struts/shocks when using drop coil springs.

So how can we increase the OEM strut compression stroke with drop coil springs?

What you think about this theory? Take a look at the two pics above. The pic of the strut rod and upper strut mount assembly. The upper strut mount assembly rest on the shoulder of the rod below the threads.

Since the upper and lower strut mount location is fixed and does not move. If the shoulder is lowered by X amount, theoretically the strut rod should be raise X amount in the strut assembly? Which should decrease the possibility of the strut bottoming out.

What do you think of that theory?
 
#10 ·
So I’m back on this project and I’ve figured out a way to get a 1” drop (maybe 1.25 or 1.5”) in the front with minimal modification to the strut and no modification to the OEM coil spring.
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I do need a favor. I seem to have lost my notes. Someone with a stock FE5 suspension. Can you measure the fender height at all four corners and let me know
 
#11 ·
I can't help you with the measurements but I went with eibach Springs and KYB's and had no problem at all. Took the car to the track last year and handled great. I only have the 2.8 liter so not much power but yesterday I just had a new magaflow muffler put on with a new resonator and feels like it has more power and definitely sounds like it. Touch slower at the hit of the throttle but then it seems to pick up a pretty decent amount after that. Today all the rear diff bushings are being replaced with aftermarket ones along with a new tranny mount with The aftermarket inserts in it. Also putting in the rubber block in the void above the diff. Also installing the K&N cold air intake setup. Also doing a new radiator before that goes out like they all seem to and some new headlights because mine have lots of little cracks in them. Going to check out the drive shaft while under there also and go over the entire suspension to make sure it's ready to go out on the track later this month. You might consider looking at doing some of the same things.

Roy
 
#13 ·
The shop that installed them and the KYB's never said anything and he would normally say something to me about stuff like that. I'm going to the shop in a little bit and I will try to remember to ask him but I don't know if he would remember because it was done a year and a 1/2 to 2 years ago.

Roy
 
#16 · (Edited by Moderator)
Since i want to lower the car. I have been reading alot about H&R springs. I see you have the 50781 set. Did you use this on a non V cadillac? Eibach doesn't make them anymore so H&R is the only way to go or coilovers.

About the shocks.. I have been looking on rockauto.com. The shocks seem to vary in length compressed or not compressed. The diameter of the shocks do vary. If you take a look at FE3 shocks from acdelco these are 1.5" in diameter. The FE4 are 1.9" in diameter. I do not know what spec KYB's are

Hope you are still looking at this thread now and then.

Edit: I forgot... The FE4 shocks have give or take 5" more length than the FE3 shocks in overall length. If you used the H&R 50781 kit for the Cadillac cts-v it may be wise to switch to FE4 shocks that will probably fix your bottoming out problem. If you still have this problem since this is an older thread. Also you cut the front spring so the front dropped even more. Hope this is helpfull to you or maybe anyone else in the future.
 
#17 ·
All your strut measurement numbers for the different chassis codes seems logical based on the issue I was having with the install.

I’ve also completed modifying my front struts to lower the front end 1” without using drop coils. You already seen the beginning pics of the strut modification. I’ll post the final pics another time

I need to change the front lower control arms first. So I purchase new control arms and yesterday I filled the void in the bushing with JB weld.
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#18 ·
So.... Did you take out the H&R springs en went back to stock? Or did you leave the rear H&R springs in place and removed just the front and swapped that to stock springs? I am very curious what your initial shock set up was on your car when you bought the H&R and why the front didn't fit on your shock. Not to insult you or doubt you. Wouldn't it be easyer to just buy the right front shocks to match the H&R springs? It looks like you are going to drive with stock front springs and H&R sport springs on te rear. I hope that doesn't have a to bad effect on the handling of the car. Do you have a V model or a normal cts? Sorry for al these questions!

Thanks
 
#19 ·
Yes, I re-install the stock springs/struts in the front and HR coils and stock struts in the rear when I ran into fitment issue

I do not have a V model but I do have the FE5 suspension. The pics I posted on the first page are of my stock front and rear GM struts. The diameter of the stock struts were bigger than the diameter of KYB struts.

The diameter difference for the front struts was barely noticeable. But just enough to have fitment issues. The diameter in the rear was VERY noticeable. So that’s why I decided to keep the stock struts. I do realize larger diameter doesn’t necessarily mean better internal valving. For me, I’m going larger is better route.

And for the record, the HR springs fit perfectly over the KYB with no fitment issues. I just wasn’t comfortable using a smaller diameter strut.

And you’re correct, there was a slight noticeable difference in ride quality with stock coils in front and HR in rear. Nothing the avg person would notice.

No worries, post all questions
 
#20 ·
Ohh i am very average on many levels... Good to know the ride quality didn't suffer to much with the stock front and H&R rear. I just ordered a set of H&R 50781 springs for my cts 3.2. Should arrive halfway december. Hope fully they arrive earlier. I do not have FE5 but FE3. Will probably switch to FE4 in the front because i'm scared to bottem them out. Not sure what i am going to do with the rears. Rear is the nivomat shocks. So i need to make a spacer or buy the MM spacer. Or even switch to fe1/2 shocks without nivomat. How is the ride with FE5 shocks? Should be even stiffer than FE4 i guess. Your car looks great lowered like that by the way! Loving those chrome cadillac wheels to.

Well good to know the H&R springs do actually lower a non v cadillac. Very curious how mine is going to look. Also curious how your project is going to turn out.
 
#24 ·
I don't know if the diameter is the same. Ride height is usually measured from lower control arm to upper wheeltubb. Because there are many types of tires and rim combo's. I do not have a car lift to get under the car. I can however measure the center of the wheel to upper center of the wheeltubb on al 4 corners. The center of the wheel should not change with different wheel combo's so that will be a pretty good start point to measure. I do not know if that will mess up your calculations. Oh couldn't find a tape measure with inches... We use the metric system. Measurements will be in centimeters and millimeters.
 
#27 ·
25 months later, today I finally installed my modified front “drop struts”

As it was designed in my head, it gave me one in drop in the front. One in drop using stock shocks and coil springs

Today I also changed the upper control arms, sway bar bushings and end links

Next on the list are the inner and out tie rods, then back to the alignment shop. I had purchased a life time alignment when I changed the lower control arms. Told them my plans of eventually rebuilding the front and rear suspension and that I’ll be back several times. They said no problem

For the longest, my LF (28”) has also been one inch higher than the RF (27”)

So after the install of my drop strut, I got 27” and 26”

Now for what you came her for, the pics 😁

First pic RF
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Second pic L
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