Vlad_Stein

Hey, there! I was wondering if people know of a shock absorber for GS430 that was designed specifically for lowered springs (i.e. short-er and stiff-er than OEM).

I've got Eibach Pro Kit springs (1'' drop) and Bilsteins. While they (Bilsteins) are stiffer than OEM, they are not what I expected: I want ~20% more compression and ~30-40% more rebound damping.
Part of the reason may be attributed to the fact that Bilstein does not make Sport shocks for GS (the shocks are designed for OEM spring length: at least that's what the guy at RMM said).

I test-drove a couple of MB models and they all (stock) have a ride that is more taut (stiffer, but not punishingly stiff) than my GS.

I am hoping that once TRD sways are in place, things will get a bit stiffer, but if they don't, does anybody know of shocks for lowered GS430?

Any info is appreciated, thanks.

P.S. Teins are out of the question, due to the fact that they are not easy to come by and if something goes wrong (which I've read, happens) then I am going to be driving a back up car for 6 months it will take to get spares from Japan.

RON430

From previous posts, it sounds like some of the Teins have not only stiffer settings than the bilsteins but are adjustable. Of course, they are coilovers but maybe they are available separately. But this is all very fascinating. A shock absorber should never reach the end of it's travel. The suspension has hard stops on both ends and the shock should never reach a stop before the suspension does. I don't think I have ever heard of a shock doing that as it would lose the battle and have a very short life in the mix. When a vehicle is lowered with shorter springs, or coilovers for that matter, the suspension travel has not increased, as far as I know. The piston in the shock may be in a different position from a not lowered vehicle but the piston doesn't care, it is always starting from its resting position. So what exactly is a shock designed for a lowering spring? I can understand getting different valving on jounce and rebound but I am interested to hear what a shock for use with a lowering spring does differently than any other shock. There are a lot more aftermarket suspension parts available now than thirty years ago but I wonder how many of these parts are designed and how many are engineered.

oldguy

Bilstein does make a sport shock for the GS. [url]www.eshock.com. and also at other sites. And someplace or other I read they are designed for shorter springs, but as RON430 points out, why should it matter what the length is?

bitkahuna

iTrader: (20)

Vlad, this is why replacing the springs without replacing the shocks makes no sense unless you ONLY want some cosmetic change.

The L-Tuned package would have done what you want for less money than you're going to pay.

Vlad_Stein

Most of what you say is true (except about the piston always starting from the resting position), but I believe that it does not contradict what I am saying.
Shorter springs result in less suspension travel (higher frequency vibrations, hence) and therefore require shocks with stiffer valving / damping to compensate. When I asked if anyone knows if there are shock applications for GS that are designed for short springs, I meant shocks that are shorter in length than OEM (so that they are not always pre-compressed as a result of length difference of the shock and the spring [the spring really should be supporting the car's wieght]) and stiffer (so that they can provide sufficient damping).

I said "short-er and stiff-er", didn't I?

Vlad_Stein

I believe that my combination is actually a bit stiffer than L-tuned.
At least that's what I've read from posts.

I will definitely check out the part numbers for my shocks and what has been suggested (tirerack.com and shox.com).

I got mine at RMM and I will be pissed if I got the wrong thing...

mooretorque

hehe

vlad, you actually said "my combination is actually a bit stiffer"


hehe

RON430

Believe me, I am not trying to start any arguments but I have been around cars for a long time and I have some questions about this shock issue.

Most of what you say is true (except about the piston always starting from the resting position),
>The piston doesn't start from rest? When does this happen? I grant that typically the shock is under constant motion but when you are talking about shock dynamics, you start with the piston stopped and make an excursion in the spring. The shock will dampen the spring excursions and, if the valving is stiff enough, provide increased force to resist suspension movement.
but I believe that it does not contradict what I am saying.

Shorter springs result in less suspension travel (higher frequency vibrations, hence)
>Shorter springs make higher frequency vibrations? Why exactly is this? Just because a shorter spring has less travel and probably higher natural frequency (although there are a lot of design issues in the spring that affect this, not length) The vibrations or excursions are typically dictated by what you are driving over, not the spring.

and therefore require shocks with stiffer valving / damping to compensate.
>Why does a higher frequency "vibration" require a stiffer valve damping? Most shocks today spend a great deal of time adjusting piston acceleration rates. The shock is damping the oscillations of the spring which would continue for much longer if there were no shock present. I know that a series of excursions can be very difficult to handle with a suspension, like a washboard, but this is from the road, not inherent in the spring or shock. Virtually all springs available today for cars are progressive with a lower initial rate and increasing, shorter springs transition faster between their extremes than a longer one. The shorter spring guys take advantage of this to lower the car and keep somewhat of a normal ride while keeping you off the bump stops with a near stock initial rate accelerating quickly to a much stiffer rate to stop the suspension. Talking about the frequency of the spring excursions gets very dicey here as you need to be concerned about where you are at in the comperssion of the spring.

When I asked if anyone knows if there are shock applications for GS that are designed for short springs, I meant shocks that are shorter in length than OEM (so that they are not always pre-compressed as a result of length difference of the shock and the spring [the spring really should be supporting the car's wieght]) and stiffer (so that they can provide sufficient damping).
>This is about 180 degrees off from my understanding of shock dynamics. There are some differences in shocks and some of the gas charged can cause the rod to extend but basically the gas pressure is there to prevent bubble formation (cavitation) in the oil. The piston is virtually always between two reservoirs of oil and the valving is what dictates how fast the piston will move by restricting the flow of oil from one chamber to the other. The oil in the chambers is not really compressed much by the piston. Cavitation means that instead of oil flowing smoothly through the piston valving, an air bubble goes through and the piston "jumps". This is the big reason for gas pressurized shocks. Now, there are all sorts of arguments about high pressure and low pressure but I do not believe the shock piston position causes much difference. Obviously, the spring is always supporting the weight of the car

I said "short-er and stiff-er", didn't I?
>I think eventually you can run into problems here but I wouldn't think that the bilstein would. I haven't really looked at the suspension geometry on the GS but I did look into coilovers and they really don't look any different in length than the standard shock but the perch is adjustable. In compression, I doubt you can lower the car enough so that it is on the bump stop. But even if you did, the shock should still not have run out of travel as that would still be the same place where a stock sprung suspension would be on the bump stop. The shorter spring has not changed the suspension geometry at the limits. While shorter springs are great for fine tuning this is also why an automotive designer or a race engineer will normally look at positioning the chassis higher or lower relative to the body for ride height adjustment and try to package as much suspension travel as possible. Once you are on the bump stops, you have no suspension. Possibly gs4will will be able to jump in here but RMM did not tell you the truth. There are both sport shocks and HD available for the GS from bilstein, I got the sport shocks through William. William, or bilstein, might be able to fill in the difference between HD and sport but my understanding is that the HDs are very close to stock. The sport setting shocks are firmer than BMW standard Boge shocks but I will say that they do not make any harshness.

Just want to understand things here. Some of these shock-spring discussions seem to never quite address the real question.

GJSGS4

Shorter springs reduce the amount of suspension travel available before the supension bottoms out. Stiffer shocks are required to prevent the suspension from bottoming out. Bilstein says to only use their sport shocks if the car has shorter springs than OEM springs. The Bilstein sports shocks are 20%-30% stiffer than Bilstein HeavyDuty shocks and the HD's are 10% stiffer than OEM.

Bilstein does make sport shocks for the GS400, not sure about the GS430. They also make HD shocks for the GS400 that should only be used with OEM length springs.

QBranchCars

As everyone else stated, Bilstein does make a sport shock. There should be no difference between the GS400 and GS430. I used to have the Eibach/Bilstein sport combo. While it is noticeably stiffer than stock initially, this is actually a good combo as far as ride harshness vs. performance, height, road noise. Give it a little time for you to get accustomed. The Teins are even stiffer than the combo.

I assume you mena the stock MB is tauter than your stock GS. The L-Tuned combo may be of the same caliber.

bitkahuna

iTrader: (20)

Sorry Vlad, my bad. I misread and thought you'd ONLY replaced the springs. Good luck.

RON430

The other shock I have had good luck with although generally I consider them a bit on the firm side for the street are Koni's. Did a brief search and they list numbers for the IS but not for the GS. A shame really, good shocks and you can get double adjustable and drive yourself crazy adjusting them. Vlad, it might be worth a call. Often the manufacturer knows the numbers that fit models they don't list in their catalog, maybe they can recommend something. They will definitely be firmer than bilstein street versions and have that adjustability.

whitels

A Bilstein dealer told me that at this time, the only Bilstein thaat you can buy in the market is the Sport version. This version was meant for lowered springs but can be used for OEM springs as well. The sport version is shorter in size but can be used definitely for OEM spring applications like RON430 had done. The HD (heavey duty) version is not available despite the fact that there is a part number available. The HD version uses or will use the same valving as the Sport version.

Vlad_Stein-
When you said you want ~20% more compression, I get the notion that you want the springs to travel 20% more? I'm just curious why? Do you want the Bilstein that you have now to allow the springs to compress 20% more to absorb the bump and therefore take care of the impact before it reaches the cabin? If so, wouldn't that translate to either a softer springs or more aggressive shock valving? I would like to understand this so folks with ideas, please jump in.

RON430

whitels - Vlad and I took the discussion off line through some PMs, I think we were feeling that maybe we were getting a little too detailed for most people's interest. I think Vlad wants more stiffness in his suspension and wants to do it through customizing the shock properties. If a double adjustable shock were available, like the koni's, he could dial in compression and rebound properties separately. Problem is, I don't know if those are available from any manufacturer for the GS. I think if Vlad finds some, he will post. With a strut suspension, the spring is mounted around the two sides of the shock piston with one side mounting to the chassis and the other mounting to a (generally lower) suspension member. A shorter spring effectively permits the lower mounting point to move up, thus lowering the car. Easier to explain if you look at coil overs although slightly different where the shock body is allowed to move up further into the spring to lower the suspension, but the effect is the same. The fully compressed stop hasn't changed on the shock but the extended portion probably has and the shorter lowering springs requires, or at least benefits from, a shorter shock. A coilover changes the mounting position of one of the spring perches and lowers the ride height. I am not sure I have totally figured out (and can explain) the suspension geometries on the GS but I spent some time with the manuals and it looks a little clearer now. Vlad feels that what you give up in compression is made up in increased rebound distance (Vlad, am I correct in saying that?) leaving the entire suspension travel the same distance but I don't think so, I think you lose that suspension travel for good. Having said all that, I think Vlads problem is that he has lowered the vehicle with a shorter spring (the way most people are doing it) and may have gotten the bilstein HD shocks and he wants to stiffen up the valving (Vlad, is that right?). An adjustable would be ideal, double adjustable double ideal, but as a stand alone shock, no one seems to know of one for the GS (maybe Tokico but I don't know if he looked into it yet). The second issue is would bilstein sport shocks give him the increased "stiffness" he is looking for. Don't know if he has reached any conclusion on that yet. Obviously I have the bilstein sport shocks and I am pretty pleased with them. Driving around with them more does not make me want to increase the spring rate though. These are right up to what I consider controlled without being harsh on the roads around here, at least combined with the TRD sways. Took a new seven out last weekend for a quick spin, while I didn't play with the electronic setup, in stock mode that puppy has definitely gone to the harsh end of the scale in my opinion. Problem is ride is such a subjective issue but I think the bottom line is that Vlad wants more stiffness than he has and wants to know what shock combined with his shorter springs is a good way to go. Hope this isn't boring everybody.

Vlad_Stein

Hey, whitels!

Thanks for the info... I followed up with the guys from RMM and they only sell sports (which confirms what you said).

I think you misread my post: I said that I wanted more compression and rebound damping, not more suspension travel.

I would only need more suspension travel if I wanted to compete with WRXs and Evo's in rally championships, or tackle Rubikon Trail.

Anybody ever heard of a monster Lexus sedan (or SUV for that matter)? Hmm... there's an idea!