Rear springs clunk with custom Bilstein setup
 

Hey all,

I've recently picked up a set of nicely used NB Bilsteins for my 92NA (Was actually purchased off of here at, Mturbo)

the specs are as follow:

NB Bilsteins
NB Top hats
QA1 550F/450R
Unknown adjustable perches (I believe its Ebay?)
Big bar front, rear bar removed
Cut NB bump stops front, no rear bump stops (Got a set of 36mm linear that I will be throwing on this weekend)
Springs droop when the car is jacked up

Anyhow, I have no complaint about ride quality or height, actually I really like them as is at the moment. one thing that bothers me a little is springs 'clunk, clank' going over sharp bumps (Highway expansion joints, irregular small bumps and dips on local roads).

Some points to mention:
- On large dips, it stays fine and quite at any speed.
- Sound is much more evident & frequent at high speeds.
- At low speed, its hard to replicate the sound.

So I thought it was the top hat nuts, UCA nuts, LCA nuts, etc.. but they were triple checked at full load and are dang on spec. So I am pretty sure its the springs.

What I am suspecting is the following:
1. Springs are high rate, thus, unload rather violently after hitting sharp irregularities, causing it to become unseated
2. Springs are not getting unseated but its just getting loose enough, hiting the adjustable collars

Possible solution that I came up with:
1. Wrap the adjustable collars with garage door sealer to decrease any possible movement of the springs that may occur, creating more of a cheap spring isolator
2. Place some cushy-cushy stuff on wherever spring gets in contact with.

Oh and Yes, I did search but I couldn't exactly find an answer, so please excuse me if I am overseeing some stuff or even better, please guide me to an answer :)


Help a newb out please !
Thank you all in advance!

Your rear rates are a little high. What length are the springs and got pics of your ride height?

Rears are 7" and unfortunately, I don't have a pic of the height at the moment.
I too felt that the rate is pretty high but its surprisingly comfy ha!

Do you have any isolators in between the top hat and spring?

Bahurd// No, no isolators as far as I know. I've looked into it and majorities of people suggested it is not needed?

Not sure that would be it as a lot of guys run without it anyway. Another thing... how firm are the sleeves to the shock body? Do the sleeves come off easy? Duct tape or rubber in between the sleeve/body?

Sleeves are on tight with tapes underneath them.
Well, I ordered a pair of isolators from amazon and got them just now.

So adding one more question about setting it up:
I see some glue it on to the top hats and some place it on top of the springs.
Which method is correct / or incorrect?

I guess either works. I put a few dabs of silicone caulk on mine and glued them to the springs when I originally built them up.

Got cha. I will try to put it on the springs and see. Thanks for the inputs!

Can you clarify this? If there's any gap between the spring and the upper spring perch at full droop, that will be your problem. Add preload until the spring stays seated when the car is jacked up. And make sure you're lifting both wheels when you check, since the sway bar will add preload of its own if you just jack one corner at a time.

If zero preload brings your ride height higher than you'd like, that means you need helper springs.

Well thanks for the input.
What I learned from searching was that having no preload at full droop is not much of an issue? Please correct me if I am wrong.l! :) (Major concensus was having loose spring at full droop doesnt matter much, I believe?)

I could put some preload and see. But other than the noise, whats the down side of running no preload, day to day basis?

Clunking if your suspension becomes fully unloaded .

Especially if you have no isolators. Metal 2 metal....

In my opinion.

Yep yep. Stupid me. :/

Anyhow, i got bumpstops and isolators added on so I will test it out for more noises tomorrow :)

It is, they're wrong. The people who say that are assuming you'll never actually hit a bump hard enough to unload your suspension.

Solution: add helper/tender springs.

Ha!
Well, I was certainly not being smart about thinking this through :P

Well, I can order a pair of helper or tender springs soon but in meantime, what is the real downside of not running it, other than NVH? Loss of traction during bumps?

Just turn the perches up so they just contact at full droop. I can't imagine you're going to affect the ride height more than a 1/2". You never said what your height is now.

You can potentially damage your suspension if the spring gets badly misaligned. Just raise it back up until you get the helpers.

Well thanks for all the tips and advises.

To follow up on this issue, for future searchers, here's what happened.

1) After installing spring isolators (Energy suspension parts. Can't remember the part number....), 36mm linear bump stops, noises did indeed decrease but somehow the car was still knocking.

2) I began to observe the sound very closely and noticed that it does not clunk much at all if I am on throttle (Even hitting same bumps, which made crazy clunking noises w/o throttle). That got me thinking it maybe related to ............. exhaust......

3) Voila! After throwing on my trust worthy hose clamps to tighten exhaust hangers, noise completely disappears. I felt like a god damned turd....................

So in the end, even if you THINK you hear springs clunk and clank, double check the exhaust hangers (My exhaust didn't show any movement when I shook it by hand FYI. So even if the hangers do not seem to be the cause of issue, double check.

Anyhow, so far so good. Suspension handles amazingly, despite the high spring rate in the rear. Great subtle drop and comfier ride vs. stock suspension. :)

Again, thank you all for the inputs!