Bilstein EDC-compatible struts for E9X M3

[lutfy]

Originally Posted by ashtaron14

She sits like this now. So far it rides well, no funny noises or unwanted movement.

Brilliant! Am ordering my Swift springs as well. Thanks mate.

Lutfy

[Black Gold]

Originally Posted by lutfy

I wrote a short snippet on another thread but here is a bit of a longer version of my review:

HD vs Sport? The different is the shorter shaft in Sport and has nothing to do with dampening/valving. So no performance benefit except being slammed.

Drive:

Lutfy

I don't write this to argue, or to call anyone "wrong", but I feel like this needs some clarification for those on here.

This is not correct. Valving is only part of the story when matching springs with dampers.

The shorter shock body/shaft is definitely important. It is specifically designed that way to be run with shorter springs, just like high end dampers like ohlins, jrz, or tck d/a shocks are shortened as they are designed for lower ride heights.

Reason being, the shocks being shorter physically allows them to not be pre-compressed with a lower ride height. For example, if you purchase the B6 shocks, which are designed for stock ride height cars, and run them with a spring that is 1" lower.......at a static ride height, the damper is already compressed 1", taking 1 full inch of travel away due to running a damper that is too tall with a spring that is too short. so now, you have both drastically reduced the amount of available travel AND are now working in a range that is not ideal.

the shorter body shocks are designed for a lower ride height so that they are NOT pre-compressed when installed with lowering springs, and thus do not suffer the same reduced travel as a B6 shock would with lowering springs.

This is why BMW uses a different strut/shock for zcp cars compared to non zcp cars. It's also why bilstein markets b6 for oem springs and b8 for lowered cars

also, the shorter body has nothing to do with the ride height. the m3 doesnt even have struts in the back, as the shocks are mounted independent of the springs in the rear.

Cliffs : if you run anything lower than OEM springs, i would go with the B8 dampers. B6 will surely be an improvement over old shocks, but they are not ideal for use with lowering springs.

[lutfy]

Originally Posted by KennyPowers

I don't write this to argue, or to call anyone "wrong", but I feel like this needs some clarification for those on here.

This is not correct. Valving is only part of the story when matching springs with dampers.

The shorter shock body/shaft is definitely important. It is specifically designed that way to be run with shorter springs, just like high end dampers like ohlins, jrz, or tck d/a shocks are shortened as they are designed for lower ride heights.

Reason being, the shocks being shorter physically allows them to not be pre-compressed with a lower ride height. For example, if you purchase the B6 shocks, which are designed for stock ride height cars, and run them with a spring that is 1" lower.......at a static ride height, the damper is already compressed 1", taking 1 full inch of travel away due to running a damper that is too tall with a spring that is too short. so now, you have both drastically reduced the amount of available travel AND are now working in a range that is not ideal.

the shorter body shocks are designed for a lower ride height so that they are NOT pre-compressed when installed with lowering springs, and thus do not suffer the same reduced travel as a B6 shock would with lowering springs.

This is why BMW uses a different strut/shock for zcp cars compared to non zcp cars. It's also why bilstein markets b6 for oem springs and b8 for lowered cars

also, the shorter body has nothing to do with the ride height. the m3 doesnt even have struts in the back, as the shocks are mounted independent of the springs in the rear.

Cliffs : if you run anything lower than OEM springs, i would go with the B8 dampers. B6 will surely be an improvement over old shocks, but they are not ideal for use with lowering springs.

I wholeheartedly agree with you. Would have gone with B8 if they came with the EDC Kit. I spoke with both Turner (where I got my shocks/struts from) and with Bikstein Motorsport in CA before trying Eibachs, per both it should be okay in this case, makes me wonder if these are actually B8 in disguise or why b8 wasn't made in the first case.... If valving is the same wondering why not have B8 which can be used for b6 application (stock springs) than the other way round?

You're spot on above.

Lutfy

[lutfy]

Originally Posted by ashtaron14

She sits like this now. So far it rides well, no funny noises or unwanted movement.

OK so I drove some 15K miles on these shocks (matched with Eibach) springs and HR front only bar. I liked that setup a lot. Comfortable (progressive springs) with sharp turn in.

Last week got the same Bilstein EDC to match with Eibach front adjustable bar (full stiff) with Swift Spec R springs.

Firstly, the car is stiffer no doubt, these springs have less initial movement (from what I have been told they are linear) which makes sense. The steering is a little bit more direct (marginally but noticeable none the less).

In DC streets, the ride is ummm, slightly compromised but overall driving experience I would say is greater (high speed ramps, crisper turnin etc.)

Looking back, I am glad I went this route. The shocks can handle the settings in all three modes (yes its noticeable) and works very well with these springs. Ride height wise, very similar to Ashtaron's car.

Having another two M3s (one with JRZ, its a street/track car, another IP race car), this is a great street setup! Granted its not as good as JRZ or MCS on track but for dual purpose I like it a lot!

Takes the guesswork out of cornerbalance etc. and the car rides very well. I have been driving this car more and more. No issues with shocks or any unwanted noises etc. BTW running with Ground Control camber plates vs factory upppermounts.

Cheers,

Lutfy

[///Mobbin]

Glad to hear this setup is working out for you! Still eyeing a Bilstein kit and hope to make a move in the not too distant future.

[Mitten3]

Originally Posted by ///Mobbin

Glad to hear this setup is working out for you! Still eyeing a Bilstein kit and hope to make a move in the not too distant future.

I have a spare front left strut for sale at a discounted price if you are looking to switch to this setup and want to save some money. Love mine on Swifts

[///Mobbin]

Originally Posted by Mitten3

I have a spare front left strut for sale at a discounted price if you are looking to switch to this setup and want to save some money. Love mine on Swifts

Appreciate it but likely going for the B16 kit.

[M3-Mike]

So I'm perfectly happy with the stock ride height of my 2008 M3, guess I don't understand why people want to mess with such a fundamental item. My issue is the factory EDC shocks are worn and the car seems to bounce around in ways it never used to.

I'm thinking of replacing all four shocks with the B6 but keeping stock springs. I assume ride heigh won't change since the springs are the same?

[GeorgeA]

Originally Posted by M3-Mike

So I'm perfectly happy with the stock ride height of my 2008 M3, guess I don't understand why people want to mess with such a fundamental item. My issue is the factory EDC shocks are worn and the car seems to bounce around in ways it never used to.

I'm thinking of replacing all four shocks with the B6 but keeping stock springs. I assume ride heigh won't change since the springs are the same?

Ride height shouldn't change. Definitely will improve the ride and handling.

[Nihilation]

The front B6 DampTronics have been back ordered forever so good luck getting you hands on a set. I did install the rears and that alone was a huge improvement over the factory EDC dampers.

My OE EDC dampers had 125k miles on them but there was still a noticable difference in ride quality between the 3 modes. After the Swift Spec R spring install the ride quality between the 3 modes had nearly vanished.

Simply replacing the rear shocks with Bilstein B6 regained clear distinction between Comfort, Normal and Sport modes. Can't wait for the front struts to arrive.

[spr]

No. the fronts raise the car. This is proven over and over. It even raised it still with lowering springs! Anyone who is telling you otherwise is a liar. (unless this has changed with a revised model.)

Also, the car handled like total garbage with the progressive lowering springs. The people saying otherwise are novices and morons with no real idea regarding proper suspension setup.

I worked with bilstein on this over and over, as I like others in this thread unfortunately followed this BAD advice. I ultimately made them take back those units and cut a deal on coil over EDC'S which are awesome and I couldn't be happier.

Originally Posted by GeorgeA

Ride height shouldn't change. Definitely will improve the ride and handling.

[GeorgeA]

Originally Posted by spr

No. the fronts raise the car. This is proven over and over. It even raised it still with lowering springs! Anyone who is telling you otherwise is a liar. (unless this has changed with a revised model.)

Also, the car handled like total garbage with the progressive lowering springs. The people saying otherwise are novices and morons with no real idea regarding proper suspension setup.

I worked with bilstein on this over and over, as I like others in this thread unfortunately followed this BAD advice. I ultimately made them take back those units and cut a deal on coil over EDC'S which are awesome and I couldn't be happier.

The E90 that was posted with swift springs a few posts up rides at the same height as my car with swift and stock EDC. It might go up 1mm maybe, not a big deal. And he has stock springs so that shouldn't matter.

[spr]

I'm providing better information as the thread misrepresents how these units actually are so that people have proper knowledge to base a decision and not get fucked and deal with the headache after the fact like I did.

Originally Posted by GeorgeA

The E90 that was posted with swift springs a few posts up rides at the same height as my car with swift and stock EDC. It might go up 1mm maybe, not a big deal. And he has stock springs so that shouldn't matter.

[GeorgeA]

Originally Posted by spr

I'm providing better information as the thread misrepresents how these units actually are so that people have proper knowledge to base a decision and not get fucked and deal with the headache after the fact like I did.

I get it, I was just mentioning that he's on stock springs, so they're not progressive. As for me, I'm on swifts and I would love to go with the B16 kit

[spr]

I almost went swift as they're linear and it would probably be ok with the replacement units. I still can't get over the fact that the car was higher with lowering Springs! Progressive Springs made it roll like a suv.

QUOTE=GeorgeA;21350978]I get it, I was just mentioning that he's on stock springs, so they're not progressive. As for me, I'm on swifts and I would love to go with the B16 kit [/QUOTE]

[lutfy]

Originally Posted by spr

No. the fronts raise the car. This is proven over and over. It even raised it still with lowering springs! Anyone who is telling you otherwise is a liar. (unless this has changed with a revised model.)

Also, the car handled like total garbage with the progressive lowering springs. The people saying otherwise are novices and morons with no real idea regarding proper suspension setup.

I worked with bilstein on this over and over, as I like others in this thread unfortunately followed this BAD advice. I ultimately made them take back those units and cut a deal on coil over EDC'S which are awesome and I couldn't be happier.

Hmmmm. I had it with Eibachs and it was neck to neck with another Instructor's E90 ZCP. I later went with Swift mostly because I am tracking it more and more (gave up street comfort a bit). Re-measured and the ride heights were literally 2mm off (Swifts were lower). I had posted pics of my car earlier as well. Fronts were NOT raised with Eibachs but were not as lowered (as advertised) either. So stock springs, will raise the car with Bilstein EDC.

Lutfy

[6ixSpd]

My ZCP with H&R Sport Plus drives like the furthest thing from an SUV with barely a hint of body roll. They're progressive springs as well. You're sweeping generalization doesn't seem valid especially when compared to the nonstop praise for these types of springs on M3s, even from the harder drivers/more knowledgeable members on this forum. It seems your quarrel is with the EDC compatible Bilstein shocks.

I've owned BMWs with PSS9, PSS10, custom valved and lengthened shocks + custom rate springs, even Ohlins and swift combo; and I without a doubt say that my ZCP shock + H&R Sport Plus combo is unbelievably effective on this car with the proper install (ie. once maintaining OE suspension travel). In fact it's the first car I've owned that's lowered on springs and actually drives damn good. All other BMWs I've had that sat on progressive springs + stock shocks drove like shit.

[SYT_Shadow]

Dammit why aren't these in stock anywhere!!

[Nihilation]

Originally Posted by SYT_Shadow

Dammit why aren't these in stock anywhere!!

Seriously. I've had an order for the front struts in since January!

[Nihilation]

Just got an email saying one of the front stuts has been shipped! Woo!

[SYT_Shadow]

good!

[MidLifeM3]

At this age of our M3s, many E9x owners will be looking for replacements of worn out stock shocks and for those of us who like to keep our EDC functionality I'm sure this thread and the related ones on B16 coilovers will be visited a lot. Although prices on OEM replacements seem to be coming down, still there will be interest in these Bilstein as an alternative to OEM. Certainly for me I was drawn to these because of Bilstein reputation as a quality shock and to address what I felt was a bit loose rebound damping on the stock EDC shocks. So all well and good ....

one question that comes up over and over an over in threads about the B6 is "will it raise my car?", followed by "how much?" Since I just went through my own analysis to try to quantify that effect, I thought for public service to the community I would share so others could have an idea what to expect.

For many on this forum the following may be obviously apparent but I'll start with the basics. All shock abosrbers, at least when new, are pressurized to suppress foaming and cavitation of the shock oil. Twin tube shocks like the OEM ones are commonly pressurized to about 100psi, while monotube shocks like the Bilsteins use a higher pressure around 300psi. As you'd expect intuitively, that pressure tends to force the shaft out of the shock body, and when installed that force will push up on the car tending to lift it slightly. But how much is that force? We need to know the relevant area to convert the psi to absolute force.

if you consider the inside of the shock, the piston (with the shaft attached to it) is sitting there inside this pressurized tube. But, the pressure is hydrostatic and because the piston has holes through it the pressure is the sameabove and below the piston. That pressure on both sides almost balances.... except for where the shaft attaches to the piston. Below the piston, the pressure pushes up on the piston surface everywhere, but above the piston the pressure can only push down on the exposed parts of the piston that are not covered by the shaft. The net force exerted on the shaft is simply the pressure in the shock times the cross-sectional area of the shaft.

For the Bilstein "inverted monotube" design note that the huge-looking cylinder sticking out of the yellow housing is not the shaft. That's the main tube, the shaft sticks out the bottom of that and is hidden inside the housing. On the stock OEM shocks (and all twin-tube shocks) in the conventional "right side up" configuration the shaft sticks out the top.

Though I haven't received my B6 yet (that pesky back order) I believe the shaft on these is 14mm. So the cross sectional area is about 0.24 sq in. Then the force exerted by 300psi is 300*0.24 = 71 lbs.

For the OEM twin-tube shocks assuming a typical 100psi pressure, the force exerted would be about 1/3 as much, roughly 24 lbs.

And for all those of us with 90k miles on our shocks, chances are good that some or most of that 100psi has leaked out by now so the force might be pretty limp. If when you remove your old shocks the shafts don't extend (even slowly) then you didn't have much pressure left inside....

On the front axle the shock and spring both have a motion ratio close to 1, and the stock front springs are about 160 lb/inch rate. compared to a fresh stock setup, the Bilstein will be pushing up with 71-24 = 46lbs more force.
46lbs / 160 lb/in = 0.3 inches, about 7mm

Compared to worn out OEM shocks with little to no pressure remaining, the delta will be larger, around 0.4" or 10-11mm.

In the rear its slightly more complex because the motion ratios are far from 1 but this is the reason why users report less lift at the rear than at the front when installing Bilsteins. The force exerted on the shock shaft is still the same, that's just determined by shaft diameter and pressure. So 70lbs or so on Bilstein, 24lbs or so on fresh OEM. The spring rate is 550lb/in, with a motion ratio of about 0.58 relative to the wheel. The shock is not concentric with the spring and has a different motion ratio - roughly 0.8 (though I admit I could get this more precise with more careful tape measure work - but close enough for this purpose). Converting both to wheel rate makes the math more intuitive
550lb/in * (0.58)^2 = 185 lbs / inch spring wheel rate
46lbs * 0.8 = 37lbs more wheel-equivalent force from the shock

Then the 37lbs wheel-equivalent more force exerted on the shaft of Bilstein vs fresh OEM results in 37/185 = 0.2" higher ride height at the rear. If your reference point is fully deflated shocks then the relative rise will be up to ~0.3" higher than your very tired worn out shocks. In either case only a little more than half as much effect at the rear as at the front.

Since Lutfy has kindly provided a rather precise description of his case we can use his experience to assess and validate these calculations. He started with a non-ZCP car and added Bilstein B6 plus Eibach springs and ended up at nearly identical to ZCP height. ZCP is 10mm or 0.4" lower than non-ZCP. the Eibachs are supposed to give 0.8" drop in front and 0.6" in rear. The B6 would counter that with 0.3" rise in front and 0.2" in rear. Net result, 0.5" drop front and 0.4" drop rear, spot on to a ZCP.

For those who use B6 with stiffer springs like the Swift, the effect of the "bilstein lift" will be a little less in proportion to the additional spring rate. The bilstein will push up by the same 70 lbs, but your sport springs with higher rate will extend a little less in response.

All of this only matters with the non-adjustable spring perches, since the coilover or sleeve-over guys can just dial up or down to whatever static ride height they want. Since unfortunately the B6 is not compatible with the sleeve-overs that trick won't work for those of us considering these shocks. If we don't like the impact on ride height our only option is to change to different springs. Or to go for the B16 coilover kit. This is purely a cosmetics question, those few 1/10's inch change in ride height will have no deleterious effect on handling, but replacing floaty worn out shocks with fresh ones will certainly be a positive improvement.

I've also seen questions of whether the high pressure shock increases the spring rate. Technically yes but the effect is smaller than the impact on ride height. The effective spring rate is due to the additional volume displaced by the shaft as it moves down into the tube, which further compresses the gas raising its pressure. The increase in pressure per inch of shaft insertion, multiplied by the 0.24 sq in of shaft cross section, is the effective spring rate due to the shock. To calculate it exactly we'd need to know the actual volume of the gas chamber which I do not have easily on hand. But considering the shaft cross-section is pretty small relative to the piston or tube cross-section this added spring rate should be fairly insignificant.

Hope this is helpful to all those out there searching the threads and wondering about the effect on ride height.

For my case, my plan is to go for the B6 along with Dinan springs (0.5" drop) and recover back to about my current ride height on well-worn OEM shocks. Otherwise the B6 look like a good match to any of the mild lowering springs out there like Eibach.


I have not seen any quantitative data on the length of the internal bumpstop of the B6 (my inquiries to Eibach have not been responded to). Nor have I seen anyone publish shock dyno results on these or OEM. I guess the guys who dyno their shocks are all focused on race shocks. But it would sure be nice for the engineering-minded to have some mroe quantitative comparisons of these aftermarket parts so we'd know ahead of time what we're getting into. Though the Bilsteins are slightly easier on the wallet than OEM, you're still looking at close to $1800 for the set of four plus labor (or an afternoon of your own time if youre the DIY type) so its not an insignificant investment to "try out and see if you like it". And the qualitative reviews are great but one guy's plush ride is another's buckboard; one guy's taut control is another's flabby boat. Pretty hard to translate to our individual expectations. If anyone out there has measurements of the bump stops, or shock dyno data on these B6, I would love to see it!

I also wonder if anyone has weighed the unsprung weight of B6 vs OEM. The B6 steel shock overall is much heavier, but since its the inverted design some of the extra weight will be sprung weight and in increased unsprung weight might not be so much worse than stock.