Hey everyone,

I finally got my new HKS Hipermax Performer coilovers installed.

I took it out for a test drive today and they seem extremely bouncy. I had watched a few youtube tutorials on how to adjust them (these have separate adjustments for both spring pre-load and ride height).

For the pre-load, everything i read and watched said just to screw the adjusting nut up against the spring so that the spring had no play and was snug.

Now my car feels kind of like it just bounces along, does this mean i have to increase pre-load or decrease it?

And also, how do I know how much to adjust it by? Is there a general rule of thumb? Should i compress the spring an inch and then take it for a spin?

 

After a little more research I think I've probably got a little too much pre-load, as I've turned the adjuster so much that I can't turn the springs by hand.

Could this be why it feels bouncy?

I guess the only other reason could just be the damping settings, but these are slightly used, and I can't imagine anyone having them set to a bouncy setting on purpose.

Now I just have to figure out how to adjust that haha, no simple **** turn like some of the others i've seen.

 

preload has NOTHING to do with anything you're talking about. jsut set it and forget it.
to tune bounciness or whatever, adjust the ***** on the top of the shocks. unless they arent adjustable, in which case deal with it.

 

Anybody else with some useful input?

 

Colin, I just installed a set of zeals this weekend and the manual says not to turn the preload more than 2 full turns from just when the spring makes contact with the perch. If you have to much preload the shock may not be able to dampen the force of the spring. I would definately lower the spring preload and then go from there. What spring rate are these coilovers?

Also, if there are no external ***** to adjust then the only way to change the damping settings would be to take the shock apart and change the valve stack.

Hope this is more helpful than the last poster.


John

 

Thanks John, that makes sense. The spring rates are 12K front and rear, so I know the ride is going to feel different in general. But not "bouncy".

I've been looking on the Sub and 350z forums, and others have had the exact same problem. The fix is always adjusting preload or just the damping (unless they bought cheapo coilovers)

These are 30 way adjustable dampening (but no ****), so i shouldn't have to take them apart. I guess the allen key will just click for each setting.

One funny thing, is that these were used, and the pre-load on the fronts were really preloaded (like 2 inches), anyone know why someone would do that? Maybe this is why it seems bouncy, the dampening may be set for the high preload (I removed most of the preload but didnt touch the dampening). Would this be so they could reduce suspension travel? (the reason why i think this is a possibility is because the height settings were very low when i first installed them)

Anyone else with some personal experience please feel free to chime in

 

i've never really played with the preload adjustable coil overs, but plenty of experience with suspensions, and racing...

i'd adjust preload so the spring just touches the collar. preload basically is like increasing the spring rate, and you don't want to do that yet. so adjust it so it touches, set ride height.

and then play with the dampers. i'd try full soft, halfway, and full stiff, and then see what works.

 

John

 

adjusting preload has NO affect on spring rate!!!

however, there's an exception: if you wind the perch up past the point where the car would normally sit. once you preload the spring past the car's own corner weight, the spring is effectively useless until is sees a higher load

eg- 400lbs/in spring, preloaded 2" = 800lbs of preload. if the corner weight is 600lbs, that corner will be stiff as a rock until you load it up in a turn. unless you just spin out first.

if your setup was indeed preloaded 2" then thats an actual possibility, although winding the spring up that high would be a pain in the *** so i dunno why previous owner would have done that (most likely reading all this preload=spring rate BS)

set the spring so its snug, and never touch it again. play with your clickers until you like it.

 

for coilovers that dont have adjustable bodies, you set your ride height with the spring perch. if you want the car higher, raise the perch. this may result in slight preload depending on the coilover/car setup, but theres no affect on the actual suspension performance.

same misconception is all over the motorcycle world- everyone knows you adjust preload on teh rear shock to accomidate a heavier rider. it doesnt change the spring rate in any way, the purpose is the raise the ride height to deal with the extra weight so the bike doesnt bottom out.

 

Somebody needs to need to lay off the caps lock, the exclamation points, and the cussing. Deal with your personal issues outside of this forum. Your repeated posts contain repeated misinformation. Politely sit down.

^This dude obviously never used a spring compressor because anyone who's ever used one will tell you it gets harder to compress the spring the further you go. The rate doesn't change, but the shorter the spring gets, the more force is required to compress it further, per the laws of physics.

I've been studying for my MCAT for the last 2 months, and everything about everything regarding physics is on it (and general chemistry and organic chemistry and human biology). So that's understanding and experience. Don't even try to challenge me on any of those topics.

Since those springs - just like my adjustable TEIN Flexes - are pretty stiff out of the box, my suggestion is to not have any preload. If the spring is 7" - like my TEINS - I'd start by setting the perch 7" from the top so there's no preload, which will reduce the bouncing. Then adjust the ride height and dampening to your liking. Chances are you probably won't want to go any stiffer on the springs unless you plan on doing more than street driving.

Good luck.

 

thats the definition of a progressive (changine) spring rate. we're talking about linear springs, as thats what most coilovers come with.

take a 100lb/in spring: put 100lbs on it, it moves 1". put 300lbs on it, it moves 3". now add another 100lbs on top of that 300lb weight, and what happens? it moves 1".

Pretty sure the MCAT doesnt involve material sciences, but mechanical engineering sure does (ask me how i know). Spring rate is a property of the spring itself (material dimensions, number of active coils).

read this:
http://www.sportrider.com/tech/146_9510_tech/index.html

and heres some guy (Duncan) attempting to explain it better than i can
http://www.motorcyclekb.com/Uwe/Foru...essive-springs

 

With coilovers that are adjustable in both preload and ride height independently here is how I do it.


1. Set the springs to zero preload.
2. Set the ride height bracket to where you like the ride height.
3. Check where your shock travel is at. I like to leave 50% for compression and 50% for extension.

If your static shock position is too extended:
You'll need to add helper springs. Compress the helper springs most of the way (1/4" from coilbind to start), then check the shock travel statically again. If its too high still, you'll need to back off on the helper preload. Continue this till the shock travel is where it should be.

If your static shock position is too compressed:
You need to preload the springs. Start with 1/8" or so preload. Keep preloading the spring till you are at 50/50 on travel.

4. Once you have finished that for each shock (front and rear), then and only then should you reset your ride height to where you want it with the ride height adjustable bottom bracket.

This is an iterative process because when you change ride height of front to rear, you'll throw off corner weights a bit and have to redo your shock travel steps. The 50/50 shock travel is just a suggestion. If you have very stiff shocks you'll probably want to leave 65 for extension and 35 for comrpession (since the springs are so stiff you'll never use more than that). I have 14k fronts, and 12k rears. I had to preload both front and rear to get the shock positioning I wanted. So unless you're using over 14/12, you probably won't need helper springs. If you do have them (like my coilovers did), then chances are you're really close to bottoming the shock out, even just statically. I did these changes mid season last autox season and went from finishing top 30/100 to finsihing top 7 or so of 100. The car is significantly more controllable now that I'm not on the bump stops in hard corners.

There are several ways to check shock travel position. Some people use zip ties. I found that difficult unless you remove the bump stops and rod covers. What I do is this:

1. Remove spring from coilover.
2. Measure distance from ground to fender arch with the shock fully extended.
3. Measure distance from ground to fender arch with the shock fully compressed (bump stop mostly compressed)
4. Take the average of those two, and bingo, thats where you should be at for 50/50 shock position. Play with preload/helpers till you get that right.
5. Then you make ride height fine tuning.
6. Go back and check your shock positioning
7. Done, enjoy your significantly better handling car.

 

P.E. California in Mechanical Engineering chiming in here.

He maybe should have phrased it more gently, but Josh is correct. Preload is a set it and forget it proposition. There's almost never a reason to screw with it and it doesn't direclty affect the bouncy feelings that the OP mentioned (unless it's way way off, which I'll get to in a second).

The vast majority of springs out there can be treated as linear rate. Consider a 250 lb / inch spring with an 8" free length. Compressing that spring one inch takes 250 lbs, two inches 500 lbs, three inches 750 lbs. This pretty much continues until you hit coil bind.

So let's say we have a 3,000 lb car with perfect corner weight that uses the above spring at all corners. At rest by definition each spring will be supporting 750 lbs of load and therefore have 3" of compression. Alternatively you could say each spring is compressed to 5" in order to achieve this load. Note, it doesn't matter whether this compression comes from load of the car or from preload. In order to see 750 lbs that spring it's going be chilling at a 5" length. Period end of story.

Now what happens when we start to dial in preload? We're compressing the spring ahead of time by moving the coil-overs perches. If you take the above car and dial in 1" of preload on all corners you only get 2" of travel until the springs hit that 5" total length number where everything is balanced. As long as you never see a load on that tire less than 250 lbs the car behaves the exact same way as it would have before. However, you have only a 2" range of possible travel in terms of extension and there a quite a few car that can corner hard enough to get a lighter load than this on the inside tire. Sometimes folks talk like limiting travel is a good thing, but we're not talking about rock crawlers here. When it comes to performance we generally want all available travel we can get. More specifically we want the ability to handle the widest range of loads possible. (If you wanted less travel it's better to jump up to a stiffer spring (a 500 lb/in spring so you only have 1.5" of travel on the extension of motion but is still capable of of handling the full range of loads).

The limit case of of preload removing possible travel that Josh already alluded to is that if you cranked in 4" of preload in our 250lb / inch example the shock won't compress at all until load on that corner exceeds 1000 lbs. This just means you have NO suspension travel and yes, this'll feel "bouncy" to say the least.

For 99% of situations the proper way to set preload is so that spring is just BARELY compressed (vs. its free length) when the shock is fully extended with the car on jackstands. Then you adjust ride height by moving the lower mount points up and down on the threaded shaft of the coilovers.

Note, if you don't move the mount point up and down then setting preload will result in change of ride height as well. Distance between mount point and spring perch is constant for whatever height the perch is set at. For the example I've been using the top of spring at rest is 5" above this. If you dial in an inch of preload by moving the perch higher the car rides higher because the top of spring is 5" above this point. The number one thing most folks screw up when adjusting coil-overs is by confusing messing with preload as a means of changing ride height. You should be moving the mount point not the spring perch.

Back tot he OP's question. The bouncy feeling is most likely your damping (overdamping feels bouncy and hard while underdamped wants to wallow and bounce repeatedly from a single suspension hit). Run over a single pothole repeately while screwing with kobs if you want to diagnose. The last thing that could be the OP's problem is running out of travel and hitting the bump stops. A zip tie on the shaft of the shock is a quick way to figure that out. That'll screw up all manner of suspension behavoir so don't get crazy with the hella flush or ride height (assuming you care about performance).

 

Kevin and Frijolee have this one covered. They are spot on.

 

Great info Kevin and Frijolee. Should help a lot of newbies trying to set up suspension.

 

Thanks guys, now I've got all the info I could ask for. Now, hopefully when someone else has the same problem they can just use the search function.

 

Okay...pretty basic question: adjust the ride height and then get an alignment? After I get it aligned, can I still play with the ride height a little bit without messing up the alignment too much?

I hear of people dropping ride height on track event days and then putting it back up afterwards...I don't think they're getting alignments every time...are they?

 

^ - I think so, I would get it aligned while you are at your track height, then when on the street its not that critical anyways.

BTW... my settings were all the way clockwise (I believe firm as possible), I've since adjusted them to 5 clicks from full counterclockwise (soft), and also taken the pre-load to two turns from no pre-load, and the ride height is set just so my wheels dont hit the fenders (lots of trial and error with tape on the fender lips to see when it rubbed).

Car rides nice and smooth now, I've got an alignement appointment on tuesday, (going to set to howard coleman's specs thread in the sticky (-1.5 degree negative camber, and a little bit of toe in) this will let me lower the car back down a touch. Then I'll be all set

Thanks again everyone for the help