hey guys,


i put on my eibach springs on maybe 10 months ago. I recently noticed that the back right is lower than the back left.

what can be attributed to this ? What should i do to fix this??

any info would help. it is really starting the bother me.

 

Make sure all the springs are seated correctly. If they are, make sure all the suspension parts appear to be in good working order and undamaged. If it's still off, you might try taling the springs into Your Eibach dealer or call Eibach to see if you can take them in for testing(they are in socal as you seem to be as well). They will replace the spring if it sags more than a certain amount(I think it was 2 mm or something). From a tour and Q&A session they held, they have reject any springs that do not meet their standards, which weem very tight.

 

Uneven drops are very common on the G35 and 350Z on the oem springs and aftermarket, not a cause for concern unless past 1/3" differance. And the rears can easily be shimmed to fix if you are compelled to do something.

 

What's the best way to do this?
Rubber donuts at the upper mount/bump stop?

 

Yep, you can cut off 3/4" then back fill with bushings you can make with hacksaw, a drill and a dremel tool.

 

Why would the G35 and 350Z be so prone to this? My thoughts are installation errors. And 1/3" difference can cause a big difference in cornerweighting. A good set of quality springs should not have this problem.

 

ckwik- It's not just limited to G35's and Z's... many cars have different corner
weights; thus the reason for coilovers to get the car corner weighted. It's a
common issue on lowering springs.

 

I'm not talking about differing cornerweights as much as I am about a change in the cornerweights as a result of a suspension change. You'd be hard pressed to find any car that has even corner weights at all 4 corners let alone any pair of wheels. The static weights of the should not change as a result of any spring but the cross weight can. Keeping this change to a minimal is probably ideal in most cases as the factory likely made sure the crossweight is withing a certain spec. Spring companies that have lose tolerances may end up with springs change the crossweight a lot. 1/3" is unacceptable to me. Considering factories probably don't try to reach the optimal 50% crossweight, it's conceivable that they can possible be closer to their minimum tolerance. Swapping the springs may cause the crossweight to be further from 50%. It also may possibly make the situation better, but it would be as a result of luck rather than good quality control and engineering. Ideally, you want no change in the corner weights as a result of swapping to lowering springs. While it's unlikely to see a 0% variance, keeping it to a very small minimum is certainly acheivable by keeping tolerances tight.

In any case, my comment was to try and get an explanation as to why Gsedan35 said this is common on the Z and G35 and that 1/3" differences can result in big changes. Particularly, the crossweight.

 

ckwkik-

>Change in the corner weights as a result of a suspension change...

well with static weight distribution, installing progressive rate springs that
are initially softer than stock linear rate are susceptible to corner ride height
changes. The softer the initial rate, the more the difference...that's just the
way it is. More of a design issue than just tolerance. You'll be better off with
near-stock rate linear lowering springs in your case...or go the extra mile
and get coilovers...or do what Gsedan35 says and shim the upper mount.
that's a good idea.

Where do you see '1/3" differences can result in big changes.' ? Am I
reading it wrong?

 

Exactly, I have had the same experience on 2 cars that I lowered with springs (Honda Accord and Lexus GS300) for my current car I chose coilovers and played with the perches for about a month, until I got it perfectly even.

I have to see a car lowered with springs that has a perfectly even drop side to side.

 

If the each set of springs(front and rear) are designed evenly then the each spring will stop compressing when the resistance sum of the resistance in the springs equals the car's weight. Progressive springs are likely to be softer at full extension, but no car I know of sits at full extension(the springs would likelt not even act as springs if this were the case). The total resistance in both the stock and aftermarket springs with just the weight of the car on the springs will be the same. The spring rate at that particular spring height will be different on the stock vs aftermarket spring. By the time you reach this height, a progressive spring should have a higher rate at the loaded height than the stock spring. At least from my experience. No quality progressive spring I've ever installed has ever been softer, even in the initial compression from the loaded height, than the OEM spring. For this reason if the springs are built consistently, then there should less difference in the loaded heights in the stiffer springs than the OEM springs. I have yet to see any ride height problems in any cars I have lowered with a set of quality springs. Many of them were Eibachs. Again, I speculate there may have been some install problems. It is certainly possible he got a defective spring, but that should be something Eibach can remedy. Shimming just should not be necessary if the springs are made correctly. And it could cause some unpredictable handling problems depending on the reason the spring is sitting lower/higher. Be aware that it can actually be the higher side that is having the problem as well.

 

>The total resistance in both the stock and aftermarket springs with just the weight of the car on the springs will be the same.

No, it will not depending on the spring rate the aftermarket springs were designed for.

>And it could cause some unpredictable handling problems depending on the reason the spring is sitting

No, absolutely not. This is equivalent to what you would do on a coilover system. The coilover itself is basically your shims.

>And it could cause some unpredictable handling problems depending on the reason the spring is sitting lower/higher. Be aware that it can actually be the higher side that is having the problem as well.

I don't know what you mean.

 

The spring rate and the resistance are 2 different things. The spring rate change in resistance that occurs for a certain increment of travel. The resistance is the total force. A spring with a 100lb/in rate will compress twice as much as a 200lb/in spring with the same weight. But the resistance would be the same since it is holding up the same weight.

I'm not sure you understand my second point correctly. I never said this was always the case, but if you are dealing with a defective spring, the rate of the spring may be off. Shimming could get you to an even ride height, but if the rate is off under this load(say the rate is lower), then as you load the suspension while making a turn, the amount of deflection would be higher and this spring would likely not be working as hard as it should. Even to the point that it may bottom out and involve the bumpstops mid-turn and cause unpredictable handling. The handling behavior turning left would be different than when you turn right as well. This is a similar problem that exists when dealing with a crossweight that is too far from 50%. My focus here is that if we are dealing with a spring that is defective, there can be some serious issues. And that if we are dealing with a spring that is built correctly, I really don't think we will see such drastic rideheight problems. Even the load at each wheel should not have changed much.


Lastly, what I was saying is that it could be that the side that is sitting lower is normal and the defective component or the problem could exist at the wheel that is sitting higher. Say if for whatever reason the rate was higher than it should be or it a coil is binding with something, etc.

 

Anyone have the actual corner weights of their G35C's?

Here are corner weights of the CPV35 taken from the TEIN website
for a right-hand drive Skyline.

LF 4040N (908lbs)
RF 4237N (953lbs)
LR 3511N (790lbs)
RR 3481N (783lbs)

LF + RR = 1691lbs
RF + LR = 1743lbs
Corner weight off by 52lbs... if no one was in the car

Left side of car = 1698lbs
Right side of car = 1736lbs
Left /Right difference = 38lbs

Ironically, the passenger side of the car is heavier than the
driver side... wonder if our car are exactly the same in the
opposite manner?

 

ckwik- my point is that our cars are not corner balanced well...so by using
progressive rate springs you're going to see the difference in drop.

Just looking at the JDM corner weights, our cars are going to rock like a chair
with one leg longer than the other 3...

LF + RR = 1691lbs
RF + LR = 1743lbs
Corner weight off by 52lbs... if no one was in the car

Let's say a 180lbs guy was in the car... that's going to be like this:
RF + LR + 180 = 1923lbs vs 1691lbs A difference of 232lbs. there is
no way a progressive rate spring is going to be able to sit straight with
that much difference in corner weights.