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      03-17-2020, 01:32 PM   #1
Heethster
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Xdrive - obvious question Thread

After much deliberating I got a 335d xDrive Touring (F31). It has the adaptive dampers.

I know this subject (xDrive being too high due to SE spec suspension) has been done to death, but it always seems to end with coilovers. That is not an option for me. Nor do I want my car slammed. Nor will I code out the dampers. I'm a petrolhead and appreciate a gentle slam (cough), but I'm also nearly 50 and have a wife and kids.

So some obvious questions.

I have no problem with the stock MSport stance. Why is no one talking about replacing their springs for the MSport springs - especially if they have adaptive dampers? They would be BMW items so only the sharpest insurance guy would know - seems like a no-brainer to me.

I find the rear isn't too high-looking. How about ONLY getting the front springs changed for shorter versions? Even 10mm would make a huge difference to the overall stance. (I find the touring's rear bulk disguises the wheel to arch gappage).

What is the best way to go given my many caveats? I'm only interested in springs PLUS I read a thread about a guy who changed an particularly weedy looking rear anti-roll bar for a thicker item - that I would also consider.

It's very strange this F30/31 stance thing. My old E90 Msport looked naturally fantastic, but even the F30 M3 has big old gaps between rubber and wheel arch at the front.
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      03-17-2020, 02:04 PM   #2
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Quote:
Originally Posted by Heethster View Post
After much deliberating I got a 335d xDrive Touring (F31). It has the adaptive dampers.

I know this subject (xDrive being too high due to SE spec suspension) has been done to death, but it always seems to end with coilovers. That is not an option for me. Nor do I want my car slammed. Nor will I code out the dampers. I'm a petrolhead and appreciate a gentle slam (cough), but I'm also nearly 50 and have a wife and kids.

So some obvious questions.

I have no problem with the stock MSport stance. Why is no one talking about replacing their springs for the MSport springs - especially if they have adaptive dampers? They would be BMW items so only the sharpest insurance guy would know - seems like a no-brainer to me.

I find the rear isn't too high-looking. How about ONLY getting the front springs changed for shorter versions? Even 10mm would make a huge difference to the overall stance. (I find the touring's rear bulk disguises the wheel to arch gappage).

What is the best way to go given my many caveats? I'm only interested in springs PLUS I read a thread about a guy who changed an particularly weedy looking rear anti-roll bar for a thicker item - that I would also consider.

It's very strange this F30/31 stance thing. My old E90 Msport looked naturally fantastic, but even the F30 M3 has big old gaps between rubber and wheel arch at the front.
Hi there
I choose to change the springs on my F36 435d GC to a set from AC Schnitzer and is very happy with the solution.
I too have the adaptive dampers and will not part with those.
When it's time to change them I might go for a set of KW DDC's that replaces OEM and still have the possibility of change between comfort and sport.
//Allan
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      03-17-2020, 03:06 PM   #3
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Quote:
Originally Posted by Heethster View Post
After much deliberating I got a 335d xDrive Touring (F31). It has the adaptive dampers.

...

I have no problem with the stock MSport stance. Why is no one talking about replacing their springs for the MSport springs - especially if they have adaptive dampers? They would be BMW items so only the sharpest insurance guy would know - seems like a no-brainer to me.

I find the rear isn't too high-looking. How about ONLY getting the front springs changed for shorter versions? Even 10mm would make a huge difference to the overall stance. (I find the touring's rear bulk disguises the wheel to arch gappage).

...
I am curious of same thing, I have an F32 Coupe xDrive and find the wheel gap (particularly the front) is way too great. I do not track, do not want to make the ride to harsh, just want to get to that M-Sport RWD height which is close to ideal IMHO. So, will the OEM M-Sport RWD 704M springs work on an xDrive with adaptive suspension?
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      03-17-2020, 05:50 PM   #4
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B6 billsteins come in active and support a small drop.

Such as
Dinan springs
Ac springs
The milder eibachs
Regular m sport or m3 springs

I'll actually soon be installing B6 adaptives with m3 springs as I don't want a crazy drop

That's a lie. I don't wanna do anything to my suspension, but my front struts are leaking... soooooo why not upgrade and diy too justify the cost !
PSA Bmw if Austin quoted 1500 USD to switch out just one !

Dinan shockwave is also an improvement
Eco comfort become similar to sport
And sport gets a special ever improved dinan setting, but there's a chance it won't take a mystery glitch they can't solve
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      03-17-2020, 06:00 PM   #5
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Quote:
Originally Posted by Heethster View Post
I have no problem with the stock MSport stance. Why is no one talking about replacing their springs for the MSport springs - especially if they have adaptive dampers? They would be BMW items so only the sharpest insurance guy would know - seems like a no-brainer to me.

I find the rear isn't too high-looking. How about ONLY getting the front springs changed for shorter versions? Even 10mm would make a huge difference to the overall stance. (I find the touring's rear bulk disguises the wheel to arch gappage).

What is the best way to go given my many caveats? I'm only interested in springs PLUS I read a thread about a guy who changed an particularly weedy looking rear anti-roll bar for a thicker item - that I would also consider.
Some of us have gone this route. I've done extensive research into the subject and highly recommend getting OE springs from different models to achieve the spring rate and height you desire. BMW OE springs can usually be had cheaper (used) than aftermarket alternatives and almost always have tighter spring rate tolerances than the aftermarket too. I typically recommend BMW OE springs to customers to come to me for suspension consulting looking to stiffen up and/or lower the ride.

The BMW F2x/F3x/F8x OE spring family has a wide range of spring rates and heights. That said, you can't just pick a spring from an M-sport car since you don't know how well the spring rate matches with your existing spring. Right now I'm using front springs from the F33 M-Perf kit on my F31 328/320d because they give me the ride height and rate that I want.

There's no issue changing JUST the front spring, but if you do that, you'll want to make sure you maintain the same spring rate as your OE spring to not throw off the front to rear frequency balance, which affects ride comfort.

I recommend if you go with shorter springs, that you also go with shorter bump stops (like the F8x ones) to maintain unimpeded damper travel before engagement.
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      03-17-2020, 06:14 PM   #6
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Quote:
Originally Posted by kpgray View Post
I am curious of same thing, I have an F32 Coupe xDrive and find the wheel gap (particularly the front) is way too great. I do not track, do not want to make the ride to harsh, just want to get to that M-Sport RWD height which is close to ideal IMHO. So, will the OEM M-Sport RWD 704M springs work on an xDrive with adaptive suspension?
I keep reading that the ACS springs result in ass-droop - and the pics I've seen seem to support that too. Not on your model, to be fair, but certainly on the touring and some F30s I've seen. I got mine serviced today at main dealer and when I went to collect it was parked next to an M3 and the M3s gap was way to big for a car of its type IMO. I'm very much anti Audi, but they get their stance spot on most of the time.

Anyway, I still don't understand why no one talks about standard MSport springs - or just lowering the front axle by half an inch.

I travel 4-up a lot of the time and like to gun it for my girls, but even gentle flexing lifts the nose like a horse on its hind legs waving it fronts in the air! sometimes you don't have time to press 'sport' first. But what an engine!
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      03-17-2020, 06:30 PM   #7
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Quote:
Originally Posted by Heethster View Post
Quote:
Originally Posted by kpgray View Post
I am curious of same thing, I have an F32 Coupe xDrive and find the wheel gap (particularly the front) is way too great. I do not track, do not want to make the ride to harsh, just want to get to that M-Sport RWD height which is close to ideal IMHO. So, will the OEM M-Sport RWD 704M springs work on an xDrive with adaptive suspension?
I keep reading that the ACS springs result in ass-droop - and the pics I've seen seem to support that too. Not on your model, to be fair, but certainly on the touring and some F30s I've seen. I got mine serviced today at main dealer and when I went to collect it was parked next to an M3 and the M3s gap was way to big for a car of its type IMO. I'm very much anti Audi, but they get their stance spot on most of the time.

Anyway, I still don't understand why no one talks about standard MSport springs - or just lowering the front axle by half an inch.

I travel 4-up a lot of the time and like to gun it for my girls, but even gentle flexing lifts the nose like a horse on its hind legs waving it fronts in the air! sometimes you don't have time to press 'sport' first. But what an engine!
I mention the m sport springs
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      03-17-2020, 08:51 PM   #8
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I'm thinking DDC from KW for my F31 Wagon. Lifetime warranty.

People seems to be fine with this solution
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      03-17-2020, 11:23 PM   #9
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Quote:
Originally Posted by Heethster View Post
After much deliberating I got a 335d xDrive Touring (F31). It has the adaptive dampers.

I know this subject (xDrive being too high due to SE spec suspension) has been done to death, but it always seems to end with coilovers. That is not an option for me. Nor do I want my car slammed. Nor will I code out the dampers. I'm a petrolhead and appreciate a gentle slam (cough), but I'm also nearly 50 and have a wife and kids.

So some obvious questions.

I have no problem with the stock MSport stance. Why is no one talking about replacing their springs for the MSport springs - especially if they have adaptive dampers? They would be BMW items so only the sharpest insurance guy would know - seems like a no-brainer to me.

I find the rear isn't too high-looking. How about ONLY getting the front springs changed for shorter versions? Even 10mm would make a huge difference to the overall stance. (I find the touring's rear bulk disguises the wheel to arch gappage).

What is the best way to go given my many caveats? I'm only interested in springs PLUS I read a thread about a guy who changed an particularly weedy looking rear anti-roll bar for a thicker item - that I would also consider.

It's very strange this F30/31 stance thing. My old E90 Msport looked naturally fantastic, but even the F30 M3 has big old gaps between rubber and wheel arch at the front.
With the F3x xDrive with Adaptive shocks I usually recommend the Eibach xDrive springs with the front 0.8" drop and rear 0.6". I have them on my 335ix. They are about 10% stiffer than stock so they add control without being harsh.

If you like the rear height now, you could just install the front springs and see how you like it. Can always add the rear later if you like.

The Adaptive shocks seem to leak at some point. You can replace in pairs which saves cash outlay. I'd recommend the Bilstein B6 Damptronic when you are ready.

Hope this helps!
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      03-18-2020, 09:00 AM   #10
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Quote:
Originally Posted by FaRKle! View Post

There's no issue changing JUST the front spring, but if you do that, you'll want to make sure you maintain the same spring rate as your OE spring to not throw off the front to rear frequency balance, which affects ride comfort.

I recommend if you go with shorter springs, that you also go with shorter bump stops (like the F8x ones) to maintain unimpeded damper travel before engagement.
Cheers FaRKle - I was with you right up until the last para. Not forgetting I'm not an engineer but love cars (like I'm not a chef but love food), I'd have thought short bump stops would mean more compression of the damper - which surely would not be good for it? Have I misunderstood?

Also, is it too simplistic to say that IF I was able to get all 4 springs from an F31 330d I should be able to replace those in my 335d Xdrive without drama (on the basis that the cars would have very similar weight - AND the fact I won't be taking the car on a track/to the ring)? Another way to ask the question is: if I had a 330d Sdrive with adaptive dampers, would the adaptive dampers be the same as those on my 335d Xdrive (but with the shorter springs)?

Oh and any views on the anti roll bar?

I'll have to look up your profile - you seem to be fairly knowledgeable (can't big you up too much!)
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      03-18-2020, 09:19 AM   #11
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Quote:
Originally Posted by johnung View Post
With the F3x xDrive with Adaptive shocks I usually recommend the Eibach xDrive springs with the front 0.8" drop and rear 0.6". I have them on my 335ix. They are about 10% stiffer than stock so they add control without being harsh.

If you like the rear height now, you could just install the front springs and see how you like it. Can always add the rear later if you like.

The Adaptive shocks seem to leak at some point. You can replace in pairs which saves cash outlay. I'd recommend the Bilstein B6 Damptronic when you are ready.

Hope this helps!
Yes it does thanks. 10% is nothing. And coming from my 325d E90 Msport it will still be comfy. Not that I didn't love my E90.
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      03-18-2020, 10:19 AM   #12
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Quote:
Originally Posted by Heethster View Post
Quote:
Originally Posted by johnung View Post
With the F3x xDrive with Adaptive shocks I usually recommend the Eibach xDrive springs with the front 0.8" drop and rear 0.6". I have them on my 335ix. They are about 10% stiffer than stock so they add control without being harsh.

If you like the rear height now, you could just install the front springs and see how you like it. Can always add the rear later if you like.

The Adaptive shocks seem to leak at some point. You can replace in pairs which saves cash outlay. I'd recommend the Bilstein B6 Damptronic when you are ready.

Hope this helps!
Yes it does thanks. 10% is nothing. And coming from my 325d E90 Msport it will still be comfy. Not that I didn't love my E90.
Photos of Eibach mild drop xDrive springs vs stock F30 springs. Front drop is 0.8", rear 0.6"
Attached Images
  
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      03-18-2020, 11:01 AM   #13
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Quote:
Originally Posted by johnung View Post
Photos of Eibach mild drop xDrive springs vs stock F30 springs. Front drop is 0.8", rear 0.6"
Thx johnung - to be honest, even though science dictates the difference will be a lot smaller under load, it looks like a huge variance in height, which is a bit unnerving.

For reference, I don't suppose you have a photo of your car side-on do you?
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      03-18-2020, 11:26 AM   #14
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Originally Posted by Heethster View Post
Cheers FaRKle - I was with you right up until the last para. Not forgetting I'm not an engineer but love cars (like I'm not a chef but love food), I'd have thought short bump stops would mean more compression of the damper - which surely would not be good for it? Have I misunderstood?

Also, is it too simplistic to say that IF I was able to get all 4 springs from an F31 330d I should be able to replace those in my 335d Xdrive without drama (on the basis that the cars would have very similar weight - AND the fact I won't be taking the car on a track/to the ring)? Another way to ask the question is: if I had a 330d Sdrive with adaptive dampers, would the adaptive dampers be the same as those on my 335d Xdrive (but with the shorter springs)?

Oh and any views on the anti roll bar?

I'll have to look up your profile - you seem to be fairly knowledgeable (can't big you up too much!)
BMW uses the bump stops for two purposes, 1) as a bump stop/buffer when the suspension would normally bottom out, and 2) as an additional spring to support the main spring for roll control. There's typically about .5-1" of travel the damper can move before the bump stop is engaged. When you lower the car, but don't change the bump stop you're reducing the amount of travel the damper can move before engaging the bump stop. This leads to early engagement, and since the bump stop is so much stiffer than the normal spring, will cause a degradation in ride quality. In other words, you're boosting the spring rate too soon, when you don't need it, and stiffer springs have higher transmissibility (transmit more vibration/shock.).

The problem with using springs from an F31 330d sDrive is the 335dx has significantly more weight up front due to the transfer case. The rear weight is the same though. As an example of how the xDrive/sDrive weight differs, for my F31 4-cyl 328/320dx the front spring that came with my car (I had the adaptive M suspension) is the exact same spring that came with a 435i sDrive with adaptive M suspension. So the weight of the transfer case is about the same as a larger engine with two more cylinders. If you'd like me to see/calculate explicitly what other springs would work for your goals you can reach out to me for the service.

For sway bars, check out my build log post about the ones I've tried. Unfortunately, you don't have many options being xDrive.
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Last edited by FaRKle!; 03-18-2020 at 04:21 PM..
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      03-18-2020, 04:46 PM   #15
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Quote:
Originally Posted by Heethster View Post
Quote:
Originally Posted by johnung View Post
Photos of Eibach mild drop xDrive springs vs stock F30 springs. Front drop is 0.8", rear 0.6"
Thx johnung - to be honest, even though science dictates the difference will be a lot smaller under load, it looks like a huge variance in height, which is a bit unnerving.

For reference, I don't suppose you have a photo of your car side-on do you?
HaHa, don't fret. It's pretty common for stock springs to be shaped like that because they are setup to be soft with a long travel. Can't eyeball them to estimate the height under load. Spring photos help more to see the thickness and quality of the Eibachs. At the time I did before and after measurements. The estimated drops by Eibach were dead on.

Attached is a car side photo. It's really tough to get the sunlight just right to properly see tire/fender gap with a black car and black tires. In the photo the Eibachs are installed which drops the car the amounts that I had stated. But I also have 245/40-18 tires (for best handling) on it in this photo. They aren't as tall as the stock 225/45-18 so it actually increases the tire/fender gap a little.

For your best solution, I'd suggest a combination of Eibach springs and a tire upgrade. If your stock tires are 225/45-18 then upgrade to 245/45-18. They provide better handling, the best comfort, AND the added benefit of filling up the tire/fender gap without dropping the car more. Summer Michelin Pilot Sport 4S tires are my favorite but if you want to stay with an all season tire you can't beat the Michelin Pilot Sport A/S 3+.

Ditching runflats makes the ride so much smoother on great roads and on potholes roads. I call runflats my old wooden wagon wheels. Attached is a photo of a Slime "8-Minute Kit" available at Walmart. It fits easily in the under floor trunk compartment.

Hope this helps!
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      03-18-2020, 05:15 PM   #16
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Quote:
Originally Posted by FaRKle! View Post
BMW uses the bump stops for two purposes, 1) as a bump stop/buffer when the suspension would normally bottom out, and 2) as an additional spring to support the main spring for roll control. There's typically about .5-1" of travel the damper can move before the bump stop is engaged. When you lower the car, but don't change the bump stop you're reducing the amount of travel the damper can move before engaging the bump stop. This leads to early engagement, and since the bump stop is so much stiffer than the normal spring, will cause a degradation in ride quality. In other words, you're boosting the spring rate too soon, when you don't need it, and stiffer springs have higher transmissibility (transmit more vibration/shock.).

The problem with using springs from an F31 330d sDrive is the 335dx has significantly more weight up front due to the transfer case. The rear weight is the same though. As an example of how the xDrive/sDrive weight differs, for my F31 4-cyl 328/320dx the front spring that came with my car (I had the adaptive M suspension) is the exact same spring that came with a 435i sDrive with adaptive M suspension. So the weight of the transfer case is about the same as a larger engine with two more cylinders. If you'd like me to see/calculate explicitly what other springs would work for your goals you can reach out to me for the service.

For sway bars, check out my build log post about the ones I've tried. Unfortunately, you don't have many options being xDrive.
Christ. Should have just gone for the 330d Touring Sdrive…
Ok, so lets ignore the bars. What about our friend 'johnung'? His first two lines appeal and he seems to know a bit also - I'm ignoring the leaking thing and will hope to be lucky!

Aren't the bumpstops also springs? How would I know which bumpstops to get? Can you recommend?

I got my car on Saturday and by Monday morning some idiot in a 1er backed into me (sensors not working...). It's all going through the insurance so I want to get the mechanics to put my new springs on while they have it.

Why could you not just have the same car as me??!! Ok, johnung's 335i? is it a decent comparison in terms of the results to expect? I'm thinking I just go with the eibach set up (maybe only the fronts as I like not having to wince each time I straddle a speed hump). I read your F8X stuff and it was brilliant by the way, but it just made me realise I'm too tired for this s%*t.
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      03-18-2020, 05:25 PM   #17
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Quote:
Originally Posted by johnung View Post
HaHa, don't fret. It's pretty common for stock springs to be shaped like that because they are setup to be soft with a long travel. Can't eyeball them to estimate the height under load. Spring photos help more to see the thickness and quality of the Eibachs. At the time I did before and after measurements. The estimated drops by Eibach were dead on.

Attached is a car side photo. It's really tough to get the sunlight just right to properly see tire/fender gap with a black car and black tires. In the photo the Eibachs are installed which drops the car the amounts that I had stated. But I also have 245/40-18 tires (for best handling) on it in this photo. They aren't as tall as the stock 225/45-18 so it actually increases the tire/fender gap a little.

For your best solution, I'd suggest a combination of Eibach springs and a tire upgrade. If your stock tires are 225/45-18 then upgrade to 245/45-18. They provide better handling, the best comfort, AND the added benefit of filling up the tire/fender gap without dropping the car more. Summer Michelin Pilot Sport 4S tires are my favorite but if you want to stay with an all season tire you can't beat the Michelin Pilot Sport A/S 3+.

Ditching runflats makes the ride so much smoother on great roads and on potholes roads. I call runflats my old wooden wagon wheels. Attached is a photo of a Slime "8-Minute Kit" available at Walmart. It fits easily in the under floor trunk compartment.

Hope this helps!
Gosh johnung - you've changed your tyre profile to improve handling? Jeez! Who the hell ARE you guys!? Your gappage looks perfect to me.

Ok so what about the bumpstop thing? Also, I've got 225 19 up front and 255 19 rear (can't recall profile, but stock). I'm considering the 19 inch 403m wheels - my absolute fave. If I get them I'll ditch the RTFs. To be honest I find the ride a lot less harsh than my old E90. But what size tyres would you get if I got the 403s (staggered)? Cheers
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      03-18-2020, 05:37 PM   #18
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Quote:
Originally Posted by Heethster View Post
Quote:
Originally Posted by johnung View Post
HaHa, don't fret. It's pretty common for stock springs to be shaped like that because they are setup to be soft with a long travel. Can't eyeball them to estimate the height under load. Spring photos help more to see the thickness and quality of the Eibachs. At the time I did before and after measurements. The estimated drops by Eibach were dead on.

Attached is a car side photo. It's really tough to get the sunlight just right to properly see tire/fender gap with a black car and black tires. In the photo the Eibachs are installed which drops the car the amounts that I had stated. But I also have 245/40-18 tires (for best handling) on it in this photo. They aren't as tall as the stock 225/45-18 so it actually increases the tire/fender gap a little.

For your best solution, I'd suggest a combination of Eibach springs and a tire upgrade. If your stock tires are 225/45-18 then upgrade to 245/45-18. They provide better handling, the best comfort, AND the added benefit of filling up the tire/fender gap without dropping the car more. Summer Michelin Pilot Sport 4S tires are my favorite but if you want to stay with an all season tire you can't beat the Michelin Pilot Sport A/S 3+.

Ditching runflats makes the ride so much smoother on great roads and on potholes roads. I call runflats my old wooden wagon wheels. Attached is a photo of a Slime "8-Minute Kit" available at Walmart. It fits easily in the under floor trunk compartment.

Hope this helps!
Gosh johnung - you've changed your tyre profile to improve handling? Jeez! Who the hell ARE you guys!? Your gappage looks perfect to me.

Ok so what about the bumpstop thing? Also, I've got 225 19 up front and 255 19 rear (can't recall profile, but stock). I'm considering the 19 inch 403m wheels - my absolute fave. If I get them I'll ditch the RTFs. To be honest I find the ride a lot less harsh than my old E90. But what size tyres would you get if I got the 403s (staggered)? Cheers
My F30 xDrive is pretty similar to your F31 xDrive. Most of the part numbers that I have looked up has listed both as compatible.

Farkle! Is the bump stop guru. I didn't need to change my bump stops based on testing that Koni did with my dampers and Eibach springs. I'd go by what Farkle! says if you change out the stock springs for Eibachs with your Adaptive shocks. If he's got a bump stop recommendation for you for that configuration, then I'd do it.

On the tire size options, read the posts from AlohaSurfToad. He helped me choose my 18" size and he was dead on. I know he has posted 19" recommendations. I just don't have them handy
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      03-18-2020, 06:07 PM   #19
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Quote:
Originally Posted by johnung View Post
My F30 xDrive is pretty similar to your F31 xDrive. Most of the part numbers that I have looked up has listed both as compatible.

Farkle! Is the bump stop guru. I didn't need to change my bump stops based on testing that Koni did with my dampers and Eibach springs. I'd go by what Farkle! says if you change out the stock springs for Eibachs with your Adaptive shocks. If he's got a bump stop recommendation for you for that configuration, then I'd do it.

On the tire size options, read the posts from AlohaSurfToad. He helped me choose my 18" size and he was dead on. I know he has posted 19" recommendations. I just don't have them handy
I was going to ask you for part number for the springs? The ones I've seen on Eibach's site say 30/15mm front to rear. The front sounds 10mm too extreme. I would even take 15/10 front/rear. I think I'll keep it simple - springs, bumpstops (depending on Farkle) and I like the idea of the strut brace - even though I'm not sure it will make a huge difference for me. Oh and go-flats IF I change the wheels.

Thank you for your advice pal.
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      03-18-2020, 06:18 PM   #20
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Johnung I've just found your original post so I presume you got the 06-22. For my car it's showing part 16-22 hence the difference in drops. Yours would have been perfect!
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      03-18-2020, 07:03 PM   #21
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I cannot find anything other than the Eibach springs I mentioned above. No idea why they wouldn't do a similarly modest drop to the one you have Johnung. Everything else I've found is 30mm+ on the front axle which is not the look I'm after. Any suggestions would be appreciated!
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      03-18-2020, 07:15 PM   #22
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Originally Posted by Heethster View Post
What about our friend 'johnung'? His first two lines appeal and he seems to know a bit also - I'm ignoring the leaking thing and will hope to be lucky!

Aren't the bumpstops also springs? How would I know which bumpstops to get? Can you recommend?
Why could you not just have the same car as me??!! Ok, johnung's 335i? is it a decent comparison in terms of the results to expect? I'm thinking I just go with the eibach set up (maybe only the fronts as I like not having to wince each time I straddle a speed hump). I read your F8X stuff and it was brilliant by the way, but it just made me realise I'm too tired for this s%*t.
Eibach will recommend the same front springs for your 335dx as they do for Johnung's 335ix. Well, actually I think they only recommend the "taller" of the two springs they option for the 335ix. The two front springs they option for the 335ix have the same spring rate (34N/mm), and the only difference is one is 10mm taller than the other. Keep in mind that the N57 is a bit heavier than the N55, so the drop will be greater than what's advertised for the 335ix.

One thing I don't like about Eibach's springs is that the rear spring is actually a tad weaker than the OE spring your car came with. If you had the base suspension (non Adaptive-M) then it'd be a bit stronger than stock, but the F31 Adaptive-M suspension rear spring is slightly stronger than the Eibach F31 spring.

As for bump stops, the F8x ones will do just fine.
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