Anyone Change Dampers Only?

[Fireflyer239]

I've done the Hotchkis front sway along with wheels and tires with great results but am looking for more high speed control (transitions, bumps, dips etc), and sharper response overall. Happy with stock sport package appearance (same susp as 135) and do not want to lower at all; this is my daily transportation and CT roads are not very friendly to lowered vehicles.

After a great and helpful conversation with a gentleman at Bilstein the other day (wrote his name down but can't recall it at the moment), I am considering a move to their HD shock/strut set. The name of the product is misleading, but it is made and valved specifically for our vehicles. Bilstein produces 2 seperate lines of shocks/struts, "HD" and "Sport". Same valving, but the Sports are for lowered vehicles, the HD is for stock vehicles. Anyway, after describing what I felt are the shortcomings of my vehicle's suspension, he felt that a change of spring might not be needed, and is not the answer to controlling suspension movement. He did comment that the stock BMW dampers are definitely built to a price point and represent a compromise in ride vs. handling. He said the problem is with a lack of low-speed damping (meaning low speed of up/down wheel/suspension movement such as in transitions through turns or over dips in the road, not low vehicle speed. An example of high speed damping would be when hitting a pothole or sharp-edged driveway, which forces the wheel and suspension to move up very quickly). This lack of low speed damping allows the car to "flop" or bounce around since the stock dampers are not adequately controlling this suspension movement.

I'm thinking that some drivers may change to stiffer/lower springs assuming they need to because everyone else does, but then get more than they bargain for (harsh ride, scraping) when what they're really after is improved control but didn't know it. Shocks/struts control the rate of suspension movement, and maybe a little bit of steady-state body lean can be acceptable as long as the chassis is composed and the driver is able to maintain excellent control, but maybe some feel that good handling means all lean should be erased? Could changing only springs result in a stiff ride and flat lower speed cornering but still leave the floppiness and bounce at higher speed? I'd rather have a more reasonable ride in normal driving but better high speed control. Stiffer-than-stock springs rebounding against weak stock dampers doesn't sound like a recipe for secure handling, nope.

So I'm wondering if it might not be a good idea to leave the springs stock and change to a high quality damper. Let's remember that in many high-end cars with adjustable suspension, it's the damper settings that are changing when you switch from "comfort" to "sport" or "sport plus"...the springs remain the same! Some of these high end cars are reported to give quite an acceptable ride in their "comfort" mode, which could only come from having reasonable spring rates. Yet, they handle superbly when in "sport" or "sport plus" mode as the dampers are firmed up.

Yes, I'm aware that coilovers may offer the ultimate answer, but even at their highest settings I think they all lower the vehicle. Please offer your comments on my theory/observation, and thanks.

[GaryS]

No one complains about harsh ride with Dinan, BMW Performance or Koni/Eibach suspension kits. I don't know if there are typically scraping problems with Koni/Eibach, but definitely not with Dinan or BMW Performance. On the other hand, lots of people have changed only the shocks to Koni FSD or Sports or Bilsteins, and most of them seem happy too. But the stock springs are soft even on 135i. I personally couldn't be happy with that much body roll.

[Fireflyer239]

I'll give some thought to the BMWP springs. I'd be willing to lower maybe 1/2" but that is all. Changing to an aftermarket or M3 front sway removes more than half of the stock body roll, which the Hotchkis has done for me. The Bilstiens will remove more, so if I would be satisfied at that level, I'd rather not do the springs. Thing is, it's easier to do the springs and the dampers at the same time. I occasionally carry clients in my car (one at a time lol) so my goal is the best balance of control and comfort I can achieve.

[GaryS]

If you use BMW Performance springs with the Bilsteins, be sure to get the Performance or Dinan bump stops too. I'm attaching a Dinan paper that explains why it's needed.

[jb2178]

Originally Posted by Fireflyer239

I'll give some thought to the BMWP springs. I'd be willing to lower maybe 1/2" but that is all. Changing to an aftermarket or M3 front sway removes more than half of the stock body roll, which the Hotchkis has done for me. The Bilstiens will remove more, so if I would be satisfied at that level, I'd rather not do the springs. Thing is, it's easier to do the springs and the dampers at the same time. I occasionally carry clients in my car (one at a time lol) so my goal is the best balance of control and comfort I can achieve.

Having a pretty similar car (and I have looked at the breytons as well) and having bought it in Rhode Island I know what you are talking about with the roads being terrible. I've considered the same because I autocross my 128 and I would like to stay in the D-Stock class which only allows the shocks and front sway to be changed, not the springs.

I'm no suspension expert but as it's been explained to me the shock absorbers are much more important to how your car handles than the springs. Sure slapping a set of tighter springs on will lower your can and make it feel tighter, but the performance of your shocks/struts is how you really change the way your suspension acts.

“Springs hold the car,” explains Lex Carson of JRZ Suspension Systems. “Shocks control the spring loading and unloading.”

http://grassrootsmotorsports.com/art...king-behavior/

I say do it, just upgrade to the bilsteins but do me a favor a write a good review on the pros/cons afterwards.

[tgxmike]

FireFlyer239, You really should get matched shocks/struts and springs. Otherwise you will either be over/under damped and loose performance. I have the BMW performance suspension, but that will cost you a lot.

Another option is BMW Performance springs and after market shocks/struts, which will provide almost no lowering.

Or just get a coil over kit and adjust the ride height to your liking. ( I think some kits can still be set fairly high)

Suspension is a very complex system, and understanding it fully requires a lot of differential equation knowledge. If you want your suspension to perform itss best, make sure that you always get yourself a matched pair of shocks/springs.

[Fireflyer239]

Originally Posted by GaryS

If you use BMW Performance springs with the Bilsteins, be sure to get the Performance or Dinan bump stops too. I'm attaching a Dinan paper that explains why it's needed.

Thanks Gary, I'll check out the link!

[Fireflyer239]

Originally Posted by tgxmike

FireFlyer239, You really should get matched shocks/struts and springs. Otherwise you will either be over/under damped and loose performance. I have the BMW performance suspension, but that will cost you a lot.

Another option is BMW Performance springs and after market shocks/struts, which will provide almost no lowering.

Or just get a coil over kit and adjust the ride height to your liking. ( I think some kits can still be set fairly high)

Suspension is a very complex system, and understanding it fully requires a lot of differential equation knowledge. If you want your suspension to perform itss best, make sure that you always get yourself a matched pair of shocks/springs.

I agree, and according to Bilstien, they've designed their HD shocks and struts to work specifically with stock springs. In fact, they offer seperate part #s for 1's and 3's due to the weight difference between the cars. They are less compromised than stock dampers, more biased toward tight handling than ride comfort, and of much higher quality. I am thinking about the BMWP springs, gonna look for some pics. Thanks.

[Fireflyer239]

Originally Posted by jb2178

Having a pretty similar car (and I have looked at the breytons as well) and having bought it in Rhode Island I know what you are talking about with the roads being terrible. I've considered the same because I autocross my 128 and I would like to stay in the D-Stock class which only allows the shocks and front sway to be changed, not the springs.

I'm no suspension expert but as it's been explained to me the shock absorbers are much more important to how your car handles than the springs. Sure slapping a set of tighter springs on will lower your can and make it feel tighter, but the performance of your shocks/struts is how you really change the way your suspension acts.

“Springs hold the car,” explains Lex Carson of JRZ Suspension Systems. “Shocks control the spring loading and unloading.”

http://grassrootsmotorsports.com/art...king-behavior/

I say do it, just upgrade to the bilsteins but do me a favor a write a good review on the pros/cons afterwards.

Thanks for the link jb, I'll check it out a bit later. At this moment, this is where my thinking is. No hard conclusions yet, but wondering if springs have been getting too much popular priority, and dampers not enough. I will update.

[zsapphire7]

Originally Posted by tgxmike

FireFlyer239, You really should get matched shocks/struts and springs. Otherwise you will either be over/under damped and loose performance.

+1000000. Having a good suspension system is a lot about having a properly damped system that matches the spring rates. I dont know how much more you can gain on stock springs. from factory the dampers should be matched quite well with the springs. Worst case theyre slightly underdamped for comfort. I dont know exactly how much difference you would notice upgrading only shocks. You would probably just end up with an overdamped setup that doesnt react with the springs at all. This is why most everyone will change out the springs and coilovers together if they care about performance.

and just to be clear, dampers have 0 effect on body roll steady state but will affect bodyroll in transition, turn in/out

[ianc]

BMW changed springs AND dampers when it designed the performance suspension for our 1's.

That should tell you something about their engineering dept's thoughts on whether it was necessary to upgrade both or not...

The PS springs would give you firmer handling, but also a very limited drop, both of which sound like what you're looking for...

ianc

[Fireflyer239]

I appreciate all the input guys, and have done a good bit of research meanwhile. I'm doing a BMW CCA Driver School at Lime Rock this Friday, with my car in the current configuration. Any change will be reflected when I go back for another track day. I don't plan on tracking or auto-xing the car much though.

I should clarify that my goal is not neccesarily to extend the absolute handling limits of my car, and will mention that the Hotchkis front anti-sway has worked wonders (best bang for the buck, hands down) so far. Body lean is much less than stock, and the car just digs in and steers into the corners now, as opposed to when it was stock and would roll onto the shoulder of the outside tire. My goal is to tighten up body motion during transitions, and when hitting bumps or tar strips during higher-speed cornering. More confidence within my operating envelope is what I'm after; I'm not cornering at the limits now, so higher limits won't do me much good.

I googled something like "upgrade shocks with stock springs" and read some posts from different forums on the general topic, but only focused on posts written by successful racers or shops that prepare cars. I also consulted with a well-respected local performance shop with lots of experience preparing cars for various types of competition.

The experts say that almost any vehicle can benefit greatly from a damper upgrade while using stock springs. Shorter springs will decrease body roll and lower the center of gravity, further improving handling in those ways. On street cars, the matching of shocks and springs has more to do with spring height (stock vs. lowered) than spring rate vs. valving. For instance, Bilstien makes 2 shocks with the same valving - Sport and HD - but the HD's are for stock spring height and the Sports are for lowered cars (different rod length or travel, not sure). The valving of a given shock will work very well within a range of spring rates. They do different jobs; you choose a spring rate, then choose to what degree you'd like to control the motion of those springs. The gentleman from Bilstien told me the shocks are valved to give the company's preferred degree of control according to vehicle weight, not specific spring rate. Also, I do comprehend that shocks will not change the steady-state degree of roll, but will slow the roll and control the rocking and rolling. While a sport package may use different shocks and springs than a base package, there is apparently much room for improvement in any case, by going to a higher quality shock. Most of what I've heard actually says upgrading dampers is the single biggest improvement that can be made to almost any stock suspension, even BMW's. Last, I want to repeat my observation from my original post that cars with adjustable suspension may have 3 shock settings...the spring is always the same but the shock is adjusted for comfort or control. This is like having 3 different shocks in one - they are all "matched" to the spring, but give different results. For the same reasons, a stock spring will work correctly with a firmer-than-stock damper, and handling will be improved with no detriment. Lower springs will improve handling even further.

All this said, I will be looking into the BMWP sport springs - I just don't want the slammed look (hey, I'm 47) and have to deal with all kinds of nasty back roads and steep driveways in my travels as a Realtor. My own observations are not meant to imply that anyone else is wrong, and I am only repeating what I have heard from honest-to-goodness experts. This stuff is what I enjoy talking about, and I love to hear all points of view. We all have different goals with our cars, which means different setups to give us each the optimum results. I will definitely report which way I go, and my perceived results.

[ianc]

The experts say that almost any vehicle can benefit greatly from a damper upgrade while using stock springs

That's true, but given the softness of our 135's springs, they'd benefit even more from a spring upgrade as well.

I know you say you are gathering info, but if you'll excuse me for saying so, from your original proposition and your subsequent posts it sounds to me like you have your mind made up already and are just trying to justify your decision. That decision is, of course, yours...

ianc

[Fireflyer239]

Originally Posted by ianc

That's true, but given the softness of our 135's springs, they'd benefit even more from a spring upgrade as well.

I know you say you are gathering info, but if you'll excuse me for saying so, from your original proposition and your subsequent posts it sounds to me like you have your mind made up already and are just trying to justify your decision. That decision is, of course, yours...

ianc

Yes, I did mention I'm aware that doing springs also would further improve handling, no doubt. And as such, if I can find some good pics of a car with the BMWP springs and feel it's not too low, I may do those. Maybe that video with the Dutch guy in the white 125?

[ianc]

if I can find some good pics of a car with the BMWP springs and feel it's not too low, I may do those

tgxmike (post #6 in this thread) had the BMW PS installed. You can search for his name to find the thread in question (can't remember if he posted pics or not), or perhaps he'll take pity on you and post some here,

ianc

[Fireflyer239]

Thanks ianc, I'll have a look!

[ianc]

Here is the thread I was thinking of. Good review, but no pics. Perhaps you could PM him and petition for some...

http://www.1addicts.com/forums/showthread.php?t=383090

ianc

[Onehp]

I had a similar question a month ago. Finally I went for the KW V2's since I didn' mind some lowering as long as comfort didn't suffer and they get so much praise. Got them yesterday and I can already see why people love them, damping so far is truly spot on!
But the matched Bilstein HD on stock springs sounds like a good route to pursue, I wouldn't lower at all if that is impractical for you and it might ruin some of that spring/damper matching!

[Fireflyer239]

Originally Posted by ianc

Here is the thread I was thinking of. Good review, but no pics. Perhaps you could PM him and petition for some...

http://www.1addicts.com/forums/showthread.php?t=383090

ianc

Thanks Man!

[Fireflyer239]

Thanks Onehp. Do you (or anyone) know what the minimum lowering is with the KW V2's? Going to do a search and try to find out on my own also.

[Onehp]

Originally Posted by Fireflyer239

Thanks Onehp. Do you (or anyone) know what the minimum lowering is with the KW V2's? Going to do a search and try to find out on my own also.

It's a minimum of 20mm (0,8") lower on all fours, which I got rear. Front I went half an inch lower since the rear was lowered with the M3 subframe bushings, so now it's level.
Some people say the KW's V1-3 are comfortable and I can agree that on a bumpy country road driving hard, it certainly feels more settled/comfortable thanks to the very well matched damping and I like that a lot (I tried changing the rebound from recommended and even one click in any direction felt worse - buy V1 you people who want the lowering). But (edit: now with some more DD driving) on a bad road there is no doubt that the harder springs are felt: harder, harsher ride and its noisier too. I guess I was hoping for a miracle there but I'll try to learn to live with it (it's not that bad), I can only imagine how good the stock springs with well matched damper would feel though. But can't have it all now can we ;-)

So I can't really recommend the V2's for your expected use and if I were you I would defenitely try a quality damper matched to your stock springs! Looking forward to your report ;-)

Cheers,
Onehp

[Onehp]

Originally Posted by Onehp

But on a bad road there is no doubt that the harder springs are felt: harder, harsher ride and its noisier too.

I take back most of that. Apparenty something went wrong at the install and the rebound on the right front was set two clicks too hard which made itself felt on broken surfaces. With the fault rectified it feels a lot better now. It still is a bit harder on the worst potholes but considering the lowering, this V2 kit is indeed amazingly good!