Simple Shocks and Springs Question

[Roku35]

Researching Shocks and Springs. I came across this description.:help

1. shock package for stock springs; Set = 2 front + 2 rear

2. shock package for Sport/lowering springs; Set = 2 front + 2 rear

I understand the difference with Stock and Sport shocks, but what about the springs? by this description, I am assuming that the Sport shocks require a different lowered springs for installation. Does that mean that you cannot mix or temporarily interchange the sport shocks with the stock springs :nono. Everything must be changed out to match at the same time?

[alpinacsi]

Why would you want to do the job twice? Just figure out what you want, get the parts and do it once.

[Alpine6And7]

I did it at the same time it will save you on labor;)

[HayekFan]

Since you haven't gotten an answer, here's what I've gathered from googling around and searching the forums. Hopefully someone more knowledgeable will correct me if I'm wrong.

I think the HD's will work with either stock or lowering springs, but Sports should only be used with lowering springs. If this is the case, then it seems like the best bet would be to get the HD's, since you'd only need one set of shocks for both spring setups.

[jbd5015]

hayekfan has got it right. if you want to keep the ride height, grab yourself a set of HD's, but if you plan on lowering the car at all in the future, make "then be now" and just get the sports and lowering springs all at once.

the main difference between the sport and HD shocks is the travel of the rods for all 4 shocks, and the adjustability of the rears. the sports are valved differently to allow for the drop better than the HD's, and with the added adjustability of the rears, you can get the exact height you want. I made the mistake of buying HD's and using lowering springs, then went back and got the sports and sold the HDs.

-Jeff

[HayekFan]

the main difference between the sport and HD shocks is the travel (http://forums.bimmerforums.com/forum/showthread.php?t=1079573#) of the rods for all 4 shocks, and the adjustability of the rears. the sports are valved differently to allow for the drop better than the HD's, and with the added adjustability of the rears, you can get the exact height you want. I made the mistake of buying and using lowering springs, then went back and got the sports and sold the HDs.That's good info because I read just the other day that there is no difference at all between HD's and Sports except the stroke. The claim was that the valving is identical and that the only drawback with HD's + lowering springs is that some of the stroke never gets used, which is pretty trivial. But it sounds like this claim doesn't jibe with your experience.

What did you find to be the problem with HD's and lowering springs? It must have been pretty pronounced if it inspired you to sell them. And when you talk about adjustability, do you mean the rear Sport shocks are adjustable for ride height where the HD's aren't?

One other thing while we're on the subject -- have you had any problems with wearing the inside edges of your tires since lowering? I've been bouncing around the idea of lowering my car but my rears already lean in noticeably and I'm wary that it will want to eat tires.

[detroit635csi]

you can run sports with factory springs or visa versa, but sports with drop springs is the way to go.. looky at my sig :)

[DaHose]

As to the HD's, I would imagine that working at pretty much maximum compression all the time would make the shock harsh and bottom frequently. A shock is typically designed to function across its range of travel and when inside a sport spring, the HD valving would need that missing third of travel to take harshness out of the ride. Sports are valved to work within that shorter travel and designed to use with lowering springs.


My M runs Bil sport and Eibach springs. It sits a full 2 inches lower than stock and I have issues with inner tire wear. To resolve it, I am machining up some spacers to go between my steering plates and strut bottoms. The machine shop at the college where I work actually offered to do the work, but if they aren't done by tomorrow I am doing it myself this weekend. I like the ride and feel of the combination. It is definitely taut, but not overly harsh and at freeway speeds it buzzes right along without excessive noise as compared to my Saturn LW wagon.

Jose

[HayekFan]

As to the HD's, I would imagine that working at pretty much maximum compression all the time would make the shock harsh and bottom frequently. I can buy this IF shocks are progressive the way springs are. I'm not sure this is the case though. I was thinking shocks were designed to have a constant damping rate that's relatively independent of compression. Maybe not though -- I can see how you might want the shock to firm up as it's compressed.

Interesting about the inner tire wear. The springs I was looking at would give a 1.5" drop in the front and 1" in the back. I wonder if that's enough to substantially increase tire wear. I'll bet it is. I know they sell eccentric control arm bushings for adjusting camber -- maybe I need to check into that.

[DaHose]

I don't mean it in terms of being a progressive damping function. I mean that a sport shock is obviously shorter, so the valving makes for compression that can take big hits within that shorter travel. An HD is valved to be "softer" (as far as I understand), so it will dampen less and bottom out.

In other words, with softer valving a hard hit will compress an HD shock at a faster rate than a sport shock and it could bottom out, since it is designed to work within a longer stroke. The M sits about 1/2" shorter than a stock 635 anywho but is within spec for the suspension geometry. I think that you would be fine with strut top adjusters even up to a full 1 1/2" drop. Once you hit 2" like mine, you end up needing more than 1/2 a degree compensation, so spacers or full coilovers are your only real options. Since I already have a great shock/strut combo, the bottom spacers make the most sense for me. If you are going from bone stock, then I say just get the coilovers and do it up right. Best of all, you can now adjust for the track or street without dismantling. Just bust out your spanner!:buttrock

Jose

[jbd5015]

the bilstein rear shocks have a c-clip and 3 adjustment settings on the HD's, and 5 on the sports. Currently i have the sports set all the way down with dinan springs and wolfie sits just great. looks like hes got a tiny bit of rake, but i think its just a visual thing as opposed to actually being higher in the rear than the front...

-Jeff

[HayekFan]

I don't mean it in terms of being a progressive damping function. I mean that a sport shock is obviously shorter, so the valving makes for compression that can take big hits within that shorter travel. An HD is valved to be "softer" (as far as I understand), so it will dampen less and bottom out.

In other words, with softer valving a hard hit will compress an HD shock at a faster rate than a sport shock and it could bottom out, since it is designed to work within a longer stroke.Okay, I see what you're saying. When you said the HD would be "harsh" with shorter springs you didn't mean it would be too firm but that it would be too soft and would tend to bottom out. Bottom line is you're saying the Sports are valved to be firmer than the HD's, which would seem to make sense since the Sports would need to absorb more shock over a shorter stroke.

However, this is at odds with what this guy, who seems to know what he's talking about, says on his blog. (http://bmwnut.blogspot.com/2006/03/e34-bmw-5-series-suspension-upgrades.html) He and a few others out there on teh intarwebs seem to think the only difference between Sports and HD's is the stroke and that the valving/firmness is the same:

"""Some Bilstein shock experts think both the HD and Sport have the same valving, but the stroke is simply shorter on the sport models. [Note: I think this sentence should be read without the comma after "valving" -- HF]. The sports are your best bet for use with lowering springs. The stroke length is considered to be unimportant for use with lowering springs according to a few BMW experts. In the past, you were led to believe that using lowering springs with standard stroke length dampers would lead to rapid shock or strut wear, but this may not be true. The throw is shorter, and fully compressed position is the same and that is what counts. The worst thing that would happen is that some of the stroke length potential is taken up and not utilized by using a shorter spring. This comes as a relief to many BMW enthusiasts concerned that using H&R or similar springs with newer stock or Bilstein HD's would have a deleterious affect on their car's suspension components lifespans."""

If this is true then I come back to my original thought, which is that the HD's are the better bet, even with lowering springs since their longer stroke lets them be used with either lowering springs OR stock springs. But I don't know if this is true. The only other thing would be the adjustability factor.

[HayekFan]

the bilstein rear shocks have a c-clip and 3 adjustment settings on the HD's, and 5 on the sports. Currently i have the sports set all the way down with dinan springs and wolfie sits just great. looks like hes got a tiny bit of rake, but i think its just a visual thing as opposed to actually being higher in the rear than the front...Was the only difference between the HD's and the Sports the 3 versus 5 step adjustability, or did you also notice a difference in their firmness?

[alpinacsi]

The problem with short springs with HD shocks/struts is that the spring my not settle properly in the seats/perches after the car has been elevated. As when serviced of if you experience extreme shock travel.


I have used the heavy duty for years with springs like the M-tech ones without any problems but these are not as short as some that are available. I do not typically use the extreme lowering springs because I am not trying to lower the car to the max point. I has had dedicated cars in the past for track use with adj. coil overs for this purpose.


You have to decide how you want to use the car and what you want to gain. For aesthetic purposes you can generally cut one coil off the stock springs and in conjunction with the adjustable settings on the rear bilsteins, you can get a nice stance without sacrificing ride quality.

[HayekFan]

The problem with short springs with HD shocks/struts is that the spring my not settle properly in the seats/perches after the car has been elevated. As when serviced of if you experience extreme shock travel. Yep, I called Bilstein today and they give this as a reason why it's better not to use the HD's with drop springs. Their main reason is as DaHose mentioned -- the HD's are valved to give a lower damping rate than the Sports, which means they're mismatched to most lowering springs since most lowering springs are stiffer than stock.