[328iX]

This is a stretch, but i can't really find any specs or dimensions for my f31 x-drive ACS lowering springs


The rear is sitting a lot lower than the front, the reverse rake is starting to bother me


I was curious if anyone would think these would work?

https://www.kwsuspensions.com/produc...-65030045.html

Please don't comment to suggest coil overs, I love how the car rides now thanks

[FaRKle!]

ACS springs are just Eibach springs. If you look at ACS' TUV documentation (from their website) they list things like # of coils, active coils, wire diameter, and spring length. Match that with the Eibach spring in Eibach's TUV doc and look at the specs/drawings/properties/test data there to see what your ACS has.

From what I recall (you'll need to verify), ACS uses Eibach's F34 (3-GT) rear springs for their F31 kits. That spring has a higher overall load rating, but I don't think it's as long, which likely leads to the reverse rake.

Also, I had my OE F31 rear spring compared to my Eibach F31 rear spring at my suspension guru's today and they have about the same spring rate. My suspension guy said that's not too uncommon where a lowering spring company will only stiffen the front rate.

[328iX]

Originally Posted by FaRKle!

ACS springs are just Eibach springs. If you look at ACS' TUV documentation (from their website) they list things like # of coils, active coils, wire diameter, and spring length. Match that with the Eibach spring in Eibach's TUV doc and look at the specs/drawings/properties/test data there to see what your ACS has.

From what I recall (you'll need to verify), ACS uses Eibach's F34 (3-GT) rear springs for their F31 kits. That spring has a higher overall load rating, but I don't think it's as long, which likely leads to the reverse rake.

Also, I had my OE F31 rear spring compared to my Eibach F31 rear spring at my suspension guru's today and they have about the same spring rate. My suspension guy said that's not too uncommon where a lowering spring company will only stiffen the front rate.

Awesome wish it was in english. it appears the inner diameter is 60mm? What are you running and do you still have the reverse rake? I don't see how they can sell a kit with such severe reverse rake, currently in contact with ACS and seeing what they can do.

Eric at the US ACS told me he'd never heard of reverse rake and requested photos and evidence which he forwarded to ACS germany for me, still waiting on their response.

[sspade]

@FaRKle! its possible that Eibach manufactures the spring but to say they are identical is incorrect.

AC Schnitzer does all of their own testing and tuning on the Nurburgring.... then possibly providing that data to a manufacturer for build.

One obvious proof of this is that the drops are different.

Quoted from another source:

"ACS has their own suspension engineer on board by the name of Manfred Wollgarten. Manfred has been making BMW suspension set ups for over 40 years and is regarded as an expert in the field. He is also the test pilot for ACS and has tested all of his suspensions on the nurburgring during the R & D process. Over the years, ACS has partnered with many suspension manufactures (Eibach, Sachs, Etc) to build Manfred's set ups. ACS makes a contract with the suspension manufactures in order to insure that their R & D is only used for the manufacturing of the ACS product. There is a difference. ACS suspensions are world renowned because of Manfred's blend of track worthy handling, with real world streetablity."

[FaRKle!]

Originally Posted by 328dX

Awesome wish it was in english. it appears the inner diameter is 60mm? What are you running and do you still have the reverse rake? I don't see how they can sell a kit with such severe reverse rake, currently in contact with ACS and seeing what they can do.

Eric at the US ACS told me he'd never heard of reverse rake and requested photos and evidence which he forwarded to ACS germany for me, still waiting on their response.

While most of it is in Deutsch, the italics are in English in that document. Rear spring IDs are 60mm, front springs are larger (you can see on the drawings). BTW "VA" are front springs and "HA" are rear. V stands for "Vor" or front, and H for "Hinter" or rear.

I'm running the front spring from the 335/340/435/440xi PN 11-20-030-03-VA with the wagon rear spring 11-20-014-14-HA. They used to recommend a different rear spring, which has the same spring rate as the updated part, but was shorter by about 7-10mm. It has a very slight forward rake with this setup, and even when I was using the actual spring Eibach recommended for my car (29N/mm vs the 34N/mm rate I'm running now) it had a forward rake.

Originally Posted by sspade

@FaRKle! its possible that Eibach manufactures the spring but to say they are identical is incorrect.

AC Schnitzer does all of their own testing and tuning on the Nurburgring.... then possibly providing that data to a manufacturer for build.

One obvious proof of this is that the drops are different.

Quoted from another source:

"ACS has their own suspension engineer on board by the name of Manfred Wollgarten. Manfred has been making BMW suspension set ups for over 40 years and is regarded as an expert in the field. He is also the test pilot for ACS and has tested all of his suspensions on the nurburgring during the R & D process. Over the years, ACS has partnered with many suspension manufactures (Eibach, Sachs, Etc) to build Manfred's set ups. ACS makes a contract with the suspension manufactures in order to insure that their R & D is only used for the manufacturing of the ACS product. There is a difference. ACS suspensions are world renowned because of Manfred's blend of track worthy handling, with real world streetablity."

You know, you can either choose to believe a marketing statement, or look at the data sheets themselves... I chose the latter. When the spring length, wire diameter, number of coils, tested load rating, ect. are the same on the data sheets do you REALLY think they're different? No.

If ACS does all their own tuning, why do they recommend the same rear springs for the 3-GT as the wagon (the rear spring PNs in those kits are the same)?

[FaRKle!]

It seems that ACS has pulled the individual spring PNs from the product pages (they only give you the kit PN now). They've also disabled the "documents" tab on the product pages with the link to their TUV testing. I guess they didn't like people like me (and these guys) looking at the data and finding out they're just rebranding Eibach springs.

The individual spring PNs can still be found easily enough on their retailers' sites if you search the kit PNs.

BTW, here's the link to their TUV documentation for the 1/2 series. Likely some of the PNs are the same as the fronts for the 3-series.

*EDIT* re-found the ACS 3-series TUV documentation.

[FaRKle!]

I found an old post of mine where I copied the TUV documentation data from Eibach and ACS' sheets and posted it. You can clearly see the ACS springs are the same as various Eibach ones.

Originally Posted by FaRKle!

Eibach F31 front spring 11-20-031-02-VA:
-Max load 1020kg
-Linear spring
-156mm outer diameter
-13mm wire diameter
-247mm unsprung length
-4.5 coils
-Spring rate 29 +/- 1.45 N/mm

ACS F31 front spring 3130231310:
-Max load 1020kg
-Linear spring
-156mm outer diameter
-13mm wire diameter
-247mm unsprung length
-4.5 coils

Eibach F31 rear spring 11-20-014-14-HA:
-Max load 1285kg
-Linear spring
-100mm outer diameter
-14.75mm wire diameter
-307mm unsprung length
-9 coils
-Spring rate 95 +/- 4.75 N/mm

Eibach F34 rear spring 11-20-031-03-HA:
-Max load 1310kg (original rating was for 1280kg, revised 11/2017)
-Linear spring
-94mm outer diameter
-14.25mm wire diameter
-300mm unsprung length
-9.75 coils
-Spring rate 95 +/- 4.75 N/mm

ACS F31/F34 rear spring 3353231130:
-Max load 1280kg
-Linear spring
-94mm outer diameter
-14.25mm wire diameter
-300mm unsprung length
-9.75 coils

[328iX]

Originally Posted by FaRKle!

I'm running the front spring from the 335/340/435/440xi PN 11-20-030-03-VA with the wagon rear spring 11-20-014-14-HA.

those part numbers are just the standard F31 kit that's being sold? Or do you mean the update changed it to the part you originally ran. So it's a 0.6/0.8" drop?

https://eibachshop.com/index.php?p24...-bmw-3-touring

[328iX]

hey FaRKle! could you answer my last post please? trying to order the eibach springs.

it looks like this kit here contains both the front and rear springs you're currently running?


I also see the 335 f31 springs you're running (11-20-030-03-VA) have an overall height of 235mm vs the 237mm on the 11-20-031-01-VA springs.. but the load rating is higher, wouldn't that make it sit lower than the 11-20-031-01-VA springs?

[FaRKle!]

Originally Posted by 328dX

hey FaRKle! could you answer my last post please? trying to order the eibach springs.

it looks like this kit here contains both the front and rear springs you're currently running?


I also see the 335 f31 springs you're running (11-20-030-03-VA) have an overall height of 235mm vs the 237mm on the 11-20-031-01-VA springs.. but the load rating is higher, wouldn't that make it sit lower than the 11-20-031-01-VA springs?

Yes that kit is the one I'm running.

As for ride height: F=kx

A higher load rating for essentially the same length spring (2mm is insignificant and within mfg tolerances) means higher spring rate (k). You can use the equation above to see which one will ride higher/lower.

[328iX]

Originally Posted by FaRKle!

Yes that kit is the one I'm running.

As for ride height: F=kx

A higher load rating for essentially the same length spring (2mm is insignificant and within mfg tolerances) means higher spring rate (k). You can use the equation above to see which one will ride higher/lower.

i'm not so worried about spring rate vs. the car being level. You can't tell me if your car sits lower or higher with the 335 spring, rather have me do an equation? lmfao

[johnung]

I've got the Eibach spring kit for xDrive installed on my 2015 335i xDrive. Eibach claims a drop of 0.8" in the front and 0.6" in the rear which is the change that I measured after the springs were installed. However this does not cause the front to sit lower than the rear because BMW sets the stock xDrive up to have a higher wheel gap in the front. I've heard people say that BMW set the suspension up that way because of the extra weight in the front of an xDrive, but I have no idea if that is accurate. It doesn't sound like any measurements have been taken, but maybe what you are seeing with your eye is this normal higher gap in the front.
Hope this helps!

[328iX]

Originally Posted by johnung

I've got the Eibach spring kit for xDrive installed on my 2015 335i xDrive. Eibach claims a drop of 0.8" in the front and 0.6" in the rear which is the change that I measured after the springs were installed. However this does not cause the front to sit lower than the rear because BMW sets the stock xDrive up to have a higher wheel gap in the front. I've heard people say that BMW set the suspension up that way because of the extra weight in the front of an xDrive, but I have no idea if that is accurate. It doesn't sound like any measurements have been taken, but maybe what you are seeing with your eye is this normal higher gap in the front.
Hope this helps!

Did you have a f31? So how does your car sit overall?
Did the lower front drop even out the factory reverse rake?

[johnung]

I have the F30 Sedan xDrive which BMW set up with a larger gap at the front wheel. The Eibach springs did reduce the difference since their front drop is 0.8" and their rear drop is only 0.6". But it still has a larger gap in the front. Attached is a photo after the Eibach springs were installed. The xDrive's are just meant by BMW to be a little higher in front.

I would imagine that the only way to even out the gap at the front and the back is to first take meticulous measurements at all four corners so that you know exactly what you are looking for. There are many different coil overs available and they have different adjustment ranges. Comparing your measurements with coilover adjustment ranges, hopefully you will find a coilover that works for you. It would probably be expensive.
Hope this helps!

[328iX]

Originally Posted by johnung

I have the F30 Sedan xDrive which BMW set up with a larger gap at the front wheel. The Eibach springs did reduce the difference since their front drop is 0.8" and their rear drop is only 0.6". But it still has a larger gap in the front. Attached is a photo after the Eibach springs were installed. The xDrive's are just meant by BMW to be a little higher in front.

I would imagine that the only way to even out the gap at the front and the back is to first take meticulous measurements at all four corners so that you know exactly what you are looking for. There are many different coil overs available and they have different adjustment ranges. Comparing your measurements with coilover adjustment ranges, hopefully you will find a coilover that works for you. It would probably be expensive.
Hope this helps!

Oh i'm not worried about having a gap, my goal is to just have an even ride, currently with my ACS springs, the front is a lot higher than the rear and it looks wonky.

I'm not trying to be slammed, just level, or even have the front slightly lower than the rear, and not the opposite, here's a picture of how it sits with ACS springs, looks terrible.

[328iX]

Here are exact measurments johnung rear 3.82" lip to fender arch, front 4.52"

[johnung]

Hmm, so you have a 0.7" or 11/16 difference front to back. Is it the same on the left side as the right side? It's been awhile since I measured mine so I just don't recall. I'll try to measure tomorrow.

[328iX]

Originally Posted by johnung

Hmm, so you have a 0.7" or 11/16 difference front to back. Is it the same on the left side as the right side? It's been awhile since I measured mine so I just don't recall. I'll try to measure tomorrow.

Yes, both rear heights match, and both front heights match, indicating it's not an installation issue (which went smoothly without issue as well) The car was aligned as well.

I contacted ACS, they did an investigation and came to the conclusion that it is normal and that's how they sit.

My goal is really to just get it as even as I can and Eibach springs are my next step, i'd probably even be fine with up to a 1/4 difference.

[johnung]

Originally Posted by 328dX

Yes, both rear heights match, and both front heights match, indicating it's not an installation issue (which went smoothly without issue as well) The car was aligned as well.

I contacted ACS, they did an investigation and came to the conclusion that it is normal and that's how they sit.

My goal is really to just get it as even as I can and Eibach springs are my next step, i'd probably even be fine with up to a 1/4 difference.

I don't recall if someone else already said this stuff in a previous post.
1) I wonder what the F30 to F31 xDrive differences are in overall weight and in f/r weight distribution?

2) I also wonder if ACS, Eibach, etc are using the exact same part# F&R springs for both the model F30 and F31 xDrives.

3) Another thought is whether the dampers make any difference in the height? I've got new Koni Special Actives. (I had other cars in the past where the shocks absolutely changed the ride height front or rear, either lower if they were worn or higher if they were new.)

Answers to those questions should help to predict the measured differences, if any, between my F30 and your F31.

[328iX]

Originally Posted by johnung

I don't recall if someone else already said this stuff in a previous post.
1) I wonder what the F30 to F31 xDrive differences are in overall weight and in f/r weight distribution?

2) I also wonder if ACS, Eibach, etc are using the exact same part# F&R springs for both the model F30 and F31 xDrives.

3) Another thought is whether the dampers make any difference in the height? I've got new Koni Special Actives. (I had other cars in the past where the shocks absolutely changed the ride height front or rear, either lower if they were worn or higher if they were new.)

Answers to those questions should help to predict the measured differences, if any, between my F30 and your F31.

I do know the F31 is heavier in the rear vs. front. It's a 49/51 split i remember reading somewhere here on the forums. My shocks aren't blown but it is a possibility they aren't as strong as they used to be.

[Watsey]

Originally Posted by 328dX

I do know the F31 is heavier in the rear vs. front. It's a 49/51 split i remember reading somewhere here on the forums. My shocks aren't blown but it is a possibility they aren't as strong as they used to be.

The weight difference between the F30 and the F31 may vary by engine and model - not all components will be ubiquitous, i.e. the brakes.

For the 330d the F31 weighs 65KG more than the F30, almost all of which will be due to the weight of the tailgate and the additional roof length.

When I had a full geo done (full fuel tank; ballasted for corner-weight adjustment) the weight distribution was 48/52% F/R. A car with a lighter engine, i.e. a 328d, will likely have a less even F/R weight distribution.

As people have found, it's difficult to get a precise F/R ride height just by swapping the springs, especially where the aftermarket parts are common across a model range. This is one of the big advantages of coilovers with separate adjustment for ride height in the damper bodies as well as spring preload.

[328iX]

Originally Posted by Watsey

The weight difference between the F30 and the F31 may vary by engine and model - not all components will be ubiquitous, i.e. the brakes.

For the 330d the F31 weighs 65KG more than the F30, almost all of which will be due to the weight of the tailgate and the additional roof length.

When I had a full geo done (full fuel tank; ballasted for corner-weight adjustment) the weight distribution was 48/52% F/R. A car with a lighter engine, i.e. a 328d, will likely have a less even F/R weight distribution.

As people have found, it's difficult to get a precise F/R ride height just by swapping the springs, especially where the aftermarket parts are common across a model range. This is one of the big advantages of coilovers with separate adjustment for ride height in the damper bodies as well as spring preload.

Well, brakes are unsprung mass shouldn't affect ride height, the 330d is also not equivalent to the U.S 328d. the U.S 328d is your 135kw 320d.

I made another thread about f31 suspension discussion that talks about the negatives of most of the "affordable" coilovers.

Once again i'm not looking for level, just closer to level than ACS, and even the front lower than the rear is fine with me. just anything other than reverse rake