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hello, i'm new here and i have a 2004 c4s tiptronic coupe. i want to lower the car about an inch. Can i just go with H&R sport springs with the stock shocks (USM030) or should i get either the Bilstein shocks with the H&R's versus ROW M030?

i drive on the street only (no track racing) at speeds up to 160 kph occaisionally but most of the time i'm at the posted speed limit.

thanks :D

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I am a firm believer that Porsche engineers spend a whole lot more time understanding the dynamics/weight balance/the whole picture if you will; of the way a Porsche should handle; than any other company on the planet.

As such, I would recommend the Porsche RoW springs. They will retain a fairly compliant ride, which can be compromised with aftermarket springs. Since you already have the US sport suspension package, the new springs will go on with no need to change anything else, seeing as ride height is the major attribute which you desire.

The RoW kit is available online at:

www.carnewal.com

The entire kit was just over a grand, and the company was great to work with.

Good luck!

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I believe that aftermarket springs are fine. I am talking about your normal lowering springs like you are considering such as H&R and Eibach etc. and not track only springs.

The biggest difference that I see between the aftermarket springs and the stock springs, aside from the fact that they are shorter, is that they are progressive. The few numbers that I have seen indicate that the aftermarket spring rates bracket the stock spring rate. So if the stock spring is 200lbs the aftermarket is 180-220lbs for example. YMMV.

The nice thing about aftermarket springs is that on the road they are a little softer so the car rides a little less harsh. However if you drive aggressively the car tightens up a little. Again the difference is very smal compared to stock as the spring rates are not that different. The main advantage is that they lower the car and the car looks better to most people. Oh and of course they are a lot cheaper than a ROW kit.

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Another thought on this. Many times the aftermarket springs lower the car too much for the stock dampers, which can cause the dampers to wear very quickly and/or fail quickly. This happened on my former 993. Additionally I found the H&R springs on the 993 to match well with the factory dampers which resulted in "choppy" ride. The ride was compliant but not controlled well because the progressive nature of the springs were not matched properly with the factory dampers.

From my past experience I would not change the springs only. The labor cost for the springs only vs. new dampers and springs is the same. Shell out a little additional cash up front and set up the ride properly not to mention you will have new dampers which you can look to as "preventive maintenance."

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Another thought on this.  Many times the aftermarket springs lower the car too much for the stock dampers, which can cause the dampers to wear very quickly and/or fail quickly. 

I have seen this explanation a number of times and it makes no sense to me. Lowering the car should not cause the dampers to fail unless the car has been lowered so much that the damper bottoms out. If someone has an explanation as to why a properly lowered car would wear out the dampers prematurely I would like to hear it.

If the spring rate is so far off so that the damper is some how over worked then I suppose that could lead to premature failure. The fact that a spring is progressive should not in and of itself be the reason for premature failure.

I know a number of people who have done spring only changes on 986s and 996s. I have not heard from anyone that they have had to replace any dampers to date. I have one car (996TT) with a spring only change with probably 6k miles since the change. I track this car so it has gotten a good workout. No problems so far.

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If spring only changes are fine, then why does the ROW M030 suspension come with different springs and dampers? Given the idea that the factory dampers are fine for aftermarket springs that lower the car and have different rates then why does Porsche have separate dampers for its springs that have different rates and only slightly lower the car from the "stock" US ride?

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If you have the US spec M030 struts (US sport package) you CAN just change the springs, however if you do not have this option, the struts AND springs must be replaced.

Different valving in the sport suspension struts.

-Sean

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Factory USA M030 dampers are different parts/numbers from ROW M030 dampers (my experience with '99 C4 and C2). Yes, M030 dampers have different damping rates releative to non-M030. USA M030 dampers ALSO have different shaft lengths (vs ROW M030's) to accomodate the 10mm different spring lengths/ride heights. I ordered and installed the ROW M030 kit on my C4 which was ordered with the USA M030 option. I measured and confirmed the different shaft lengths. Apparently the factory considers it important to match the ride height to damper stroke/location within the damper.

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There are two issues.

First does lowering the car cause the damper to exceed its operating range? If not then the car will not bottom out the damper and no damage will occur.

Second does the spring rate differ significantly enough from the stock spring rate such that the damper/spring dynamics are adversely effected?

Again the few numbers that I have seen show that the aftermarket springs rates are within 10% of the stock rates.

You can buy matched set of shocks and dampers if it makes you feel better. There are a lot of people that have done spring only changes and there are no mass reports of problems. If you do not track your car the vast majority of people wont even notice the difference.

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Great discussion thanks guys. i checked with carnewall's people and they said i could go with just the RoW springs with the US/Canada M030 stock suspension (at least with the C4s). I thought a lot about it and i think i will go with the H&R's (which give 25mm lowering vs. 10mm for the RoW springs). I just think that 10mm won't be noticeable enough. I'll make the change in the spring because it's time to store the vehicle for the winter (i'm in Canada eh!) I'll give my feedback when i do the change...stay tuned

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911driver-- Where are you getting your H+R springs from? I'm in Edmonton and looking for a reasonable Canadian supplier.

Thanks

Brad

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You can buy matched set of shocks and dampers if it makes you feel better. There are a lot of people that have done spring only changes and there are no mass reports of problems. If you do not track your car the vast majority of people wont even notice the difference.

You are correct there are many people who do opt for the spring only switch and don't report any problems. However this does not mean it is necessarily an optimized set up.

I had the spring only set up on my former 993 (H&R springs done by the prior owner). It looked great and the ride seemed fine when I bought the car. Since purchasing that car I had the opportunity to drive some other 993’s with varying suspension setups. It became clear that the spring only switch utilizing the factory dampers was not the best set up. The lowering of the car improved some handling characteristics and the gave the car a very “sporty” feel; however, the unmatched springs and dampers resulted in a rather “bouncy” and "uncontrolled" ride when compared to other set ups. I admit I didn’t notice the bounce until I drove cars with different suspension set ups. These cars had a much better controlled ride with much less “bounce” especially over uneven pavement (on the streets not the track). When I had a rear shock failure I elected to replace the entire suspension instead of just the shocks.

I have never been happy with the ride height of my 996. However I learned my lesson on the 993 and have investigated alternatives by driving and riding in cars with various set ups. IMO the spring only (H&R springs with US standard shocks) set up on the 996 is similar to my experience in the 993. Yes it lowers the car and it looks much better (IMO) and the lower ride height does offer some handling advantages; however, I have also found that something is just not quite right with ride when compared to the ROW M030, X74 or some of the coilover set ups. These set ups usually offered a more controlled ride (although I thought some of the coilover set ups were just too harsh for daily driving duties on roads were I live).

Many of the people that ask about suspension set ups do not realize what the alternatives and why there are such alternatives. Since the original poster was asking about a 2004 and he is concerned about the ROW M030 not lowering the car enough, he should also consider the X74 suspension offered by Porsche. It is lower than the ROW M030 set up; however, it is harsher than the M030. The factory does a lot of testing and suspension tuning, it is hard to go wrong with the factory setups for street use.

Edited by bet

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"he should also consider the X74 suspension offered by Porsche. It is lower than the ROW M030 set up; however, it is harsher than the M030."

Harsher than the US or ROW MO30?

Though it is a firmer ride, X74 provides a substantially more controlled and less harsh drive. If I'm being stupid it will certainly hit the bump stops faster but in 95% of my driving its materially less harsh than the US MO30 that came with the car.

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I need your opinions, since I have read conflicting information in various sources. Got a set of Eibach springs in the garage, and was toying with the idea of replacing the stocks with these. I do track the car, and was looking to go a little faster in the twisties, lower the COG, etc.

I can imagine and understand a shock being compressed, having the fluid past the valve in the air chamber. As a spring-dashpot effect, the more fluid would act as more incompressible fluid in the expansion chamber, higher pressure for the remaining fluid to enter the chamber has to have a bumpier ride, harsher absorption. Not sure if that does have a long term effect on the shocks, can't imagine how it would unless the constant pressure in the valve creates a different failure through static pressure instead of cyclic?

Regardless, what is the experience out there with just changing springs and keeping standard US shocks?

Izzy

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As long as we're talking opinions, I can certainly see that the dampening effect though valving should be matched to the spring rate.

There is doubtless some optimum combination for each spring-shock that Porsche has found. That being said, I am still planning to put H&Rs on my C4S this winter.

The C4S springs and shocks are somewhere between C2 stock and M030.

I am gong to try the H&R sport springs. My existing ride with 19" whls is quite stiff and the progressive rate may help. I don't track the car so I don't expect the non optimum setup will be noticeable. I am hoping for a fairly similar feeling ride with a much more meaner stance ( 1" really changes the look) . If I was to track the car and really push it , I would go to adjustable coil overs.

Eric

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getting just springs installed is the cheap way out, and the trade off is ride quaility. I use to be the type that swore on how good it rode on just springs, but that's because i didn't know better, and after having proper suspension set-up i would never go back to using only lowering spring again.

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I need your opinions, since I have read conflicting information in various sources. Got a set of Eibach springs in the garage, and was toying with the idea of replacing the stocks with these. I do track the car, and was looking to go a little faster in the twisties, lower the COG, etc.

I can imagine and understand a shock being compressed, having the fluid past the valve in the air chamber. As a spring-dashpot effect, the more fluid would act as more incompressible fluid in the expansion chamber, higher pressure for the remaining fluid to enter the chamber has to have a bumpier ride, harsher absorption. Not sure if that does have a long term effect on the shocks, can't imagine how it would unless the constant pressure in the valve creates a different failure through static pressure instead of cyclic?

Regardless, what is the experience out there with just changing springs and keeping standard US shocks?

Izzy

I have used the eibachs before and can tell you that it works fine for most street driving. However at the track the stock shocks can not control the spring rates well enough in quick transition especially when there is an elevation change. See shocks really don't change handling at steady stae handling suchs as a skid pad, but when you are changing direction quickly the shocks do affect handling by affecting the quickness of weight transfer from one wheel to another. IMO using springs are fine for lowering a car that won't see track work. Izzy you should get a set of bilstein HD or Sports for that eibach. FWIW some people thinks that the M030 shocks are perfectly match to the spring, but if you look up the Panorama article on M030 suspension at pca.org you will find some interesting things. The ROW and US M030 springs have the same spring rate the only difference is the height of the springs. However the shocks have different valving with the front US M030 that has even softer setting than the standard US shocks. The rear M030 for both US and ROW were stiffer than the US standard, with the US M030 softer than ROW. The point of this is that the shocks are not perfectly match to the spring rates, but tuned to the idea of what Porsche thinks is appropriate for each target market. Putting springs on stock shocks may ride fine for some people, but not for others.

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Keep in mind the the piston length and travel are different for each the US std, US sport ( ROW std) and ROW sport suspension. The front bump stops are the same for all 3. The rear bump stocks are unique for each application with the US std being the tallest and the ROW M030 being the shortest. What this means is you are much more likely to bottom or run on the bump stops with US std shocks than US M030 or ROW M030 with lowered springs.

Also keep in mind that Porsche individually matches the compression and rebound rates to correspond with the ride heights, spring rates and lengths for each of the production set of springs. These components are unique whether the car is a coupe, convertible, targa, 2WD or 4WD or even if it is a manual or tip. Aftermarket is one-application-fits-all. A 2WD cab tip can weigh 400 lbs more than a 2WD Coupe manual or over 10% more weight. Should it use the same suspension components? If you deviate from this, there is no guarentee that the dampening will be correct and if there are any problems then Porsche has no warranty obligations. If you swap to a complete ROW M030 suspension, Porsche will still warranty all components. Will H&R replace your shocks if their springs blow them out? No.

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I'll give feedback when i've driven the car some more. The c4s came with the US sport M030. I have kept the original springs (only 12 000 Km on them) just in case i'm not happy. The car rides softer with the H&R's on it for sure which is nicer for the street but it does feel a little less "on rails" in corners. I don't really push the car to the limit though.

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here's the car with the H&R's on the original M030 shocks

rides great

Car looks great I have an 02 C4S and am planning the same mod as you did maybe this winter.

The H&R description says 1" drop. I imagine that this is from stock US height.

When you said M030 shocks , did you mean the original C4S shocks and if so how much drop did you realize? I thought that the C4S was supposed to be 10 mm lower than stock anyway?

Any chance you could measure your tire OD and height from ground to top of fender lip front and back so I could compare to try to determine where I will end up?

Thanks

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I just installed the H&R's on my 2002 C2 Coupe (have factory installed US Spec M030). So far, I am pleased with the appearance and ride. I will try to post some pics soon.

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here's the car with the H&R's on the original M030 shocks

rides great

Car looks great I have an 02 C4S and am planning the same mod as you did maybe this winter.

The H&R description says 1" drop. I imagine that this is from stock US height.

When you said M030 shocks , did you mean the original C4S shocks and if so how much drop did you realize? I thought that the C4S was supposed to be 10 mm lower than stock anyway?

Any chance you could measure your tire OD and height from ground to top of fender lip front and back so I could compare to try to determine where I will end up?

Thanks

i'll do the measurements this weekend after i wash and wax the car and i'll post some better pics.

i am pleased with the ride so far. no bottoming out, the cornering seems better than when i first drove it after the lowering. i've received more compliments on the look/stance of the car since lowering.

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