Suspension Gurus, please chime in.

[ATK_Designs]

I'm experiencing extremely stiff and bouncy on my rear suspension. This is on the aftermarket Coilover systems. The brand shall remain nameless until I get it resolved, but they're pretty reputable.


Here are some quick information.

Monotube Design.
18 ways damping adjustable.
Right height adjustable.
12Kg/mm front and 8Kg/mm rear (100% stiffer in the front and 28% stiffer in the rear)

The rear suspension is the 2 pieces design (springs and shocks are separated).

Rear shocks have adjustable collar (see attached pic - Furthest one to th eback).

During installation, I noticed the the rear shocks are higher than OEM. Right now, at the rear has 6 (out of 18) damping seting and 1.25" lowered, the car is very stiff and very bouncy.

The front is okay, smooth and not bouncy at all (1.5" lowered and at 3/18 damping setting).

Now my questions are:

1. Is the stiffness and bounciness in the rear caused by the springs or the shocks?
2. Could it be that the shock is initially set to be higher than OEM, which caused to compress a whole lot more when the car is on the ground, thus, not much vertical/damping movement, causing a negative effect?
3. If 2 is the reason for the harsh ride, should I lower the shocks body to OEM's height (FYI: this will not affect ride's height as the springs are on a separate location)? I know that these are valved to the rates of the springs, would that be changing the valving/damping of the shocks?

Thanks

Attached pics is a generic pics for reference only. It is NOT my coilover.

Notice that the front is one piece coilover and the rear has the shocks and springs separate.

[Vteckidd]

the new shocks were TALLER than OEM?

i had this problem with my previous OMNIPOWER coilovers on my old CRX. All civic 88-00 suspension is the same. However, the CRXs use a SMALLER strut LENGTH wise. Omni neglected that fact an his first batch were too long.

I got one of those sets, and it was about 3 inches TALLER than my OEM struts. what this meant was that i had to shorten the strut ALL THE WAY, and compress the coilovers almost all the way for it to lower the rear AT ALL. This causes suspension travel problems and a SHITTY ride. Bouncy as fuck, and i hated it.

does this sound like your issue?

[ATK_Designs]

Thanks Mike,

Since mine are separate pieces, I didn't have to compress the springs at all. Springs are free to travel to their designated rate.

It's the shock that I had to compressed to get it in - It's about 1-2" taller than stock.

From the look of it, I may need to lower the shock body to prevent it from compressing to much (initially)

[typerek]

you will get a hard bumpy ride if the spring is a really tuff track spring.

[ATK_Designs]

you will get a hard bumpy ride if the spring is a really tuff track spring.

These springs doesn't have that much higher spring rate. As I stated, the rear is only ~28% stiffer than OEM. Even with the front as twice as stiff, it wasn't that bumpy.

What I'm thinking is that the shocks compressed TOO much thus doesn't have room for damping movement, causing it to be really stiff. I'll try to shorten the shock body and see what'll happen.

[nofive-0]

Sounds like the shocks

[Big Baller]

Ok a couple of questions, the adjustments that youre shocks have, are they compresion or rebound or does it adjust both together, what exactly are the spring rates and what car is this on.

Matt

[Big Baller]

Oh and are the springs linear rate or progresive

[ATK_Designs]

BB-

The car is a Infiniti G35.

Spring rate is 8kg/mm for the rear.

They're Linear springs.

Damping adjustment: I'd have to double check.

[Big Baller]

well first you have to keep in mind that you're stock springs were not linear rate, so the Man. rating was based off the highest part of the progressive rate. So you're new springs are actually a lot stiffer than your stock ones were,...Some Man. do still use linear front springs, I'm not sure if infinity is one of them. I would suggest backing the damping all the way down to zero and taking a spin and then putting it on full stiff then at least you have some idea what you're working with.

Matt

[ATK_Designs]

Problems solved:

There's some clarification I'd like to make.

1. The Rear shocks body was a little taller than stock. However, it wasn't that much taller than stock, 2" like I measured.
2. The measured 2" was when I took them fresh of the box compared to fresh removed OEM's shocks.
3. I measured again this evening, it's almost the same, if not, about half a inch taller than OEM's.

However, the problem is just like I suspected.

1. Since the rear is lowered about 1.25", this take away 1.25" of movement on the shock body.
2. By keeping the shock height the same as stock, it'll be compress when the car is lowered, this limit the damping, rebound (vertical) movement.

So, to solve the problem:

I lowered the shock's tread body to about 1.25" (which is the max I could lower it anyways). Now, the shock is fully able to travel according to its correct valving. The ride is totally different. It handles like a dream, smooth, little stiff, but NO bouncy, yet remain the stock's like feeling. I'm now set at 6/18 front driver, 4/18 front passenger, and rear driver @ 6/18, rear passenger @ 3/18 and it's very smooth. Will try to up the settings on the rear to about half way and 2/3 fore a lil more oversteer. The way I set it up like this is because I'm the only person on the car 80% of the time, which makes it handles a lot more balance for my taste.

Thumbs up for Function and Form Type II coilovers. However, they still have some improvement that they need done on their designs. For example: The rear damping adjustment is impossible on my car, Infiniti G35C. The only way is to remove the wheels, remove the shocks, adjust it and reinstall it back it. Which takes lots of time (20min/side with hand tools only).

This system is by far one of the best I've experienced (after corrected the issues).

It's more comfort than JIC FLT-A2, HKS RS, Tein Flex, etc. but handles very much like those track system. Will try to fine tune it and push it more this weekend.

Thanks guys for the helps.

[Big Baller]

Good stuff, glad you got it figured out.

Matt