[stevesingo]

All,

I would like to canvass some thought on my logic.

I would like to refresh all the suspension on my E90 2007 330i M Sport (Euro), new bushes, arms, springs and shocks. I would like to use Bilstein B8 shocks and stock springs (I want good ride comfort), but the cost of replacement springs is just silly in comparison to Eibach for example. The problem for me is that all aftermarket springs offer a drop from stock, which I don't want. The Eibach pro are -30 front and -25mm rear (from stock suspension, MSport is -15mm already, so I would be looking at -15mm Fr and -10mm rear), which just about the least drop you can get from aftermarket springs.

The B12 Pro kit is essentially B8 dampers and Eibach Pro springs.

The B12 Pro kit is available for various different models, but the only difference is the springs. Luckily the TUV papers for the B12 and Eibach springs sets out the different spring rates for different models, so I began to wonder if there was the option of using a non E90 6cyl petrol B12 kit to retain zero drop? And, I think I can.

Bilstein Data http://web1.carparts-cat.com/default...230=9997&1231=

TUV Data https://media.carparts-cat.com/pdf/E...057-E0-024.pdf

The possible corresponding springs below with their respective max axle loads. It stands to reason that the cars with higher axle loads have higher spring rates.

I can't Format this in to a table, but here is the data:

________________________________Axle____Wire___Fre e___Coils__Rate
________________________________Load____Dia____Len gth______N/mm
11-20-013-02-VA____6cyl P Front____1045kg___12_____263___4.75__18.8
11-20-014-04-VA-___6cyl D Front____1090kg___12.25__273____5____19.5
11-20-013-01-HA____4/6cyl Rear____1135kg___14.25___307___9.25__72.6
11-20-014-05-HA____4/6cyl Touring__1200kg___14.5 ___310___9.75__74.5

The rates are not in the TUV, but using the TUV data you can calculate them using http://www.reliablespring.co.uk/calculator.htm

Next the calculations of wheel load vs spring load and length.

Wheel loads were estimated from the manufacturer's data, being

E90 330i = 1550kg 50/50% weight distribution of 775kg on each axle and 387.5kg per wheel.

Using the motion ratio I calculated that the spring loads are

Front 3955N
Rear 5164N

Using the above calculator I inputted the free length until I got the same load on each of the front springs.

11-20-013-02-VA 52.8mm
11-20-014-04-VA 68.35mm

The difference being 15.55mm. The difference this makes to wheel position can be calculated from the motion ratio again, and we het 16.2mm increase in ride height from the 330i spring to the 330d spring. Considering I would be looking at -15mm from Eibach Pro in my MSport, the use of the 330d Eibach Pro springs will give me + 1.2mm in ride height. I think I can live with that.

Using the same logic, I looked at the other spring available, the Touring specific 11-20-014-05-HA

The difference on this spring is + 1.1mm on the stock MSport set up.

So, does anyone have any comments?

[snedanator]

I get ur logic on the spring rates from the other bmw types to try and keep the same ride height, not sure if anyone has even though of that or even tried it...but in theory it should work. The other options are spring pads or thicker spring perches, or metal shims, basically for adjusting the height to suit urself but keeping the same dampening characteristics of the shocks and the same spring rates when installed?

[gjm120]

Op - good work and this could be very useful.

I can follow your calculations, but, how did you match the spring version number in the TUV document with the part numbers in the online catalog ?

[stevesingo]

Originally Posted by snedanator

I get ur logic on the spring rates from the other bmw types to try and keep the same ride height, not sure if anyone has even though of that or even tried it...but in theory it should work. The other options are spring pads or thicker spring perches, or metal shims, basically for adjusting the height to suit urself but keeping the same dampening characteristics of the shocks and the same spring rates when installed?

The damper part numbers from Bilstein are the same across all 6cyl engines and chassis.

[stevesingo]

Originally Posted by gjm120

Op - good work and this could be very useful.

I can follow your calculations, but, how did you match the spring version number in the TUV document with the part numbers in the online catalog ?

The TUV papers for the B12 state the spring numbers.

[snedanator]

Ur theory in using diffrent springs from another model to urs will probably give u what u are looking for regarding to not drop the car low but it won't be the correct spring rate to what ur car needs! Or am I missing something?

[Spitfire007]

Can't you find a set of stock sport springs on here that someone could sell you for cheap?
And try B6s with stock sport springs.
Works for me, though I may switch out to something a bit more compliant for comfort.

[gjm120]

Originally Posted by stevesingo

The TUV papers for the B12 state the spring numbers.

Right but for example the spring part number for the E90 330i is 37-161293 from the Bilstein catalog. The article number on the TUV sheets are numbers like 11-20-013-02-VA. What I'm getting at is if one has the spring part number from Bilstein catalog, how to find the TUV document?

[stevesingo]

Originally Posted by snedanator

Ur theory in using diffrent springs from another model to urs will probably give u what u are looking for regarding to not drop the car low but it won't be the correct spring rate to what ur car needs! Or am I missing something?

From the Wiki on here stock M-Sport springs are;

Front- 25.4N/mm or 145lb/in

Rear- 80.7N/mm or 460lb/in

The B12 kit for 6cyl E91 are;

Front- 21.3N/mm or 121lb/in

Rear- 74.5N/mm or 426lb/in

Which is contrary to what it states here... https://www.e90post.com/forums/showthread.php?t=235797

So slightly softer than M Sport or the same. Either way, I don't mind.

Edit: Thinking about this, is it not more likely the stock springs are 25/80Nmm? I can't see the Germans making springs using SI units of an odd number.

[stevesingo]

Originally Posted by Spitfire007

Can't you find a set of stock sport springs on here that someone could sell you for cheap?
And try B6s with stock sport springs.
Works for me, though I may switch out to something a bit more compliant for comfort.

I have an old set of stock springs. By rights, they shouldn't degrade over the design life if designed correctly. Not so sure that is the case when 12yrs old and having been subjected to the UK coastal weather and shitty roads.

[stevesingo]

Originally Posted by gjm120

Right but for example the spring part number for the E90 330i is 37-161293 from the Bilstein catalog. The article number on the TUV sheets are numbers like 11-20-013-02-VA. What I'm getting at is if one has the spring part number from Bilstein catalog, how to find the TUV document?

Try this http://web1.carparts-cat.com/default...F018001&12=140

Scroll to the bottom of the page and click Certificate:TU 025057-E0-024

[gjm120]

Originally Posted by stevesingo

Try this http://web1.carparts-cat.com/default...F018001&12=140

Scroll to the bottom of the page and click Certificate:TU 025057-E0-024

No such option is there. Maybe it's loading a different page.

[stevesingo]

OK, I see it takes you to the manufacturers list page.

From there, click BMW.

Then click 3 Series Saloon (E90) or 3 Series Estate (E90 sic).

Click 330i or 330d

Click Suspension.

Click Suspension kit complete.

Click BILSTEIN - B12 Pro-Kit 46-****** number in bold and you should get a pop out. At the bottom of the pop out, you will find a link to the TUV.

[Tr1ppy]

Originally Posted by Spitfire007

Can't you find a set of stock sport springs on here that someone could sell you for cheap?
And try B6s with stock sport springs.
Works for me, though I may switch out to something a bit more compliant for comfort.

@OP I have a set of the stock MSport springs that came off my E93 330i at 62k miles if you're interested?
Just been sat in storage so good condition.

[stevesingo]

Thanks,

mine have done 80k miles, but the issue I have is I don't want to reuse old springs and find when I'm done with replacing all the bushes, bearings and arms that one is sagging or some such.

[shuotong]

Spring doesn't degrade though, why not reuse your old one? Mine looks as dirty as mud be but once I wiped them it doesn't look that bad.

[stevesingo]

I might do yet. I'll measure the free lengths and compare side to side.

[=C=]

stevesingo

I recently installed front and rear new struts and went with Sachs OE replacement for the M-sport and kept the original springs.

I also replaced the rear mount lower and all mount upper to the Monroe harder rubber. Car feels like new and didn't cost me an arm and a leg to do it. I also wanted to retain the same m-sport ride height as I too didn't like the extra lowering with the B7's etc...

[stevesingo]

Well,

I've bit the bullet and ordered the E91 Touring 6cyl diesel B12 Pro kit.

Along with, new front arms, top mounts and ancillaries to build up the struts before fitting. All new rear arms, sub frame bushes, spring pads, shock mounts, bolts and fasteners, and an ebay sources rear sub frame to I can build it all up best I can prior to fitting.

Scheduled to dive in to it weekend 4-5 May.

[Nautinto]

Hi there!

Interesting topic. I was thinking the same, but on an E92 coupé 330i (N52K engine). What would happen if I'd put the B12 kit for 330d on my car?

Comparing the two B12 kits, it seems the only difference are the front springs, which on the 330d version are 1cm longer while otherwise being identical (same diameter, same wire diameter, same number of coils, both are linear..). Axle loads are rated 990kg for 330d vs. 930kg for the 330i.

Would the spring length difference translate to less drop proportional to spring length? (330d spring 263mm vs. 330i 253mm).

I would not wish to lower the car more than what the M-Sport chassis does (max 25mm), and also I do not like the stance where the front is lower than the rear aesthetically.

Additionally my car is loaded with heavy options, engine block heater, Webasto, Active Steering, Sunroof... Surely these have an effect too? Manual transmission though.

[juld0zer]

I conjured up the idea of using 330d E93 stock springs with B8 to get a firmer rear on an E92 335i too. It's a fairly unicorn donor car which put the idea to bed

[stevesingo]

Originally Posted by Nautinto

Would the spring length difference translate to less drop proportional to spring length? (330d spring 263mm vs. 330i 253mm).

You would end up with a compressed spring length 10mm longer. So about 9.3mm additional ride height.