[FaRKle!]

There seems to be more interest now on retrofitting F8x springs to F3x cars, but a lot of "unknowns" in the community about them. I hope to make things more transparent on the F8x springs option.

Introduction/Framework

The F8x cars (F80/82/83) have two "suspensions/classes" of springs. They are the "base" suspension and "ZCP/competition pack" suspension. Within each class of springs are two more sets of springs that are tied to how the car was optioned. The front spring selection is tied to is the transmission (DCT vs manual) and for the rear spring it's the roof (sunroof or no sunroof). For the F83 there's only one rear option per spring class.

Since the spring config depends on the weight, the higher weight option springs have a slightly higher spring rate, by about 2-3%. For example DCT front springs are slightly stiffer than manual transmission fronts, and sunroof rear springs are slightly stiffer than plain roof rears.

The F80/82 use the same springs, and the F83 has a whole different set due to its much higher weight.

The differences between the classes of springs (base vs ZCP) are mainly spring rate, where the ZCP springs are stiffer by about 10-15%. Additionally, the ZCP rear springs are progressive, while the base suspension springs are linear (like F3x springs). Both base suspension and ZCP springs give the same ride height.


Spring Identifier Codes

BMW springs can be identified by the two letter code on the barcode sticker on each spring. Below are the configs and barcode identifiers.

Front springs:

• F80/82 Manual: MA
• F80/82 DCT: MB
• F80/82 ZCP Manual: MP
• F80/82 ZCP DCT: MQ
• F83 Manual: MG
• F83 DCT: MH
• F83 ZCP Manual: MV
• F83 ZCP DCT: MW

Rear springs:

• F80/82 Plain Roof: MC
• F80/82 Sunroof: MD
• F80/82 ZCP Plain Roof: MR
• F80/82 ZCP Sunroof: MS
• F83: MI
• F83 ZCP: MX

F3x Applications

So how does this translate to the F3x series of cars? Well, it's important to keep in mind the design and weight of the F8x cars. For example, putting F8x front springs on a 4cyl front RWD F3x isn't a great idea. The front end is much lighter, and you may end up gaining ride height. Like-wise, putting F80/82 rear springs on an F31 or F34 with significantly higher rear weight is likely going to put you too low, or lower your ride frequency too low compared to the front. F8x cars have lower ground clearance (4.7" vs ~5-5.7" for most F3x), so you'll want to consider that as well if thinking about ride height.

Below are my thoughts on how F8x springs might pair with various F3x cars (speculation) based upon what I know about these vehicles' weights and spring rates.

4cyl RWD F30/32/36
F8x front springs probably aren't a good idea. The lighter front end means you may gain ride height. Rear F80/82 springs might be fine and slightly lower.

I don't think any of these cars should go higher than F80/82 base suspension spring rates because the damper tuning isn't likely strong enough for ZCP rates.

6cyl RWD F30/32/36
F80/82 springs should give you an increase in front spring rate and a bit lower. I wouldn't expect a lot lower though, at maybe 0.6" or less. F80/82 rear springs should do similar as the front.

F80/82 base suspension spring rates should be fine with these dampers. ZCP spring rates are probably close to the edge of what the dampers can acceptably do (EDC has a more head room though, even more so with shockware).

4cyl xDrive F3x
F80/82 front springs should work with the extra weight of the transfer case up front, but I wouldn't expect much lowering (F30/31/32/36). Look for springs from manual transmission F80/82 cars to avoid ride height gain. I expect the same ride height as stock to about 0.5" of drop. F34s should check how close their front weight is to the other F3x cars to see if it'll lower more (likely).

F30/32 should be able to use F80/82 rears fine for ride height. F36 is a bit heavier in the back, but should still be OK height-wise. F31/34 shouldn't use F80/82 rears without spacers/shims, and I don't recommend ZCP rears since the progressive travel isn't well matched. F83 rear springs might work for the F31/34, although you'd need to check the weight (F31 might not really lower with F83 rears since the F83 is heavier in the back).

F30/31 base suspension dampers shouldn't be paired with more than F80/82 springs, and those are probably right on the line. EDC dampers should be able to use F80/82 base suspension rates fine and likely ZCP too.

F32/36 all suspensions' dampers should be able to use F80/82 base suspension rates. Front ZCP rates are probably fine on both, but F32 rear dampers might not handle ZCP rear springs all that well.

6cyl xDrive F3x
F80/82 base suspension front springs will be close to stock spring rates, so might not do much for handling, but would lower (and probably a bit more than for 6cyl RWD cars). F83 front springs will probably lower a bit (like the F80/82 springs for 6cyl RWD cars) and be stiffer.

For the rear springs, F80/82 springs should pair the same on F30/32/36 as the RWD models. F34s, the same as in the 4cyl xdrive section probably applies.

Everything except the F30 base suspension dampers should handle F80/82 base suspension spring rates. For ZCP rates I think F32/36 dampers and F30 EDC dampers should handle the fronts acceptably, and for the rears F30 EDC and F36 should be OK. F32 rears probably shouldn't use ZCP rear springs.


What I've Tried

Here are the springs I've tried on my own vehicle (F31):

• F80/82 DCT front
• F80/82 ZCP Manual front
• F80/82 ZCP DCT front
• F80/82 ZCP Plain Roof rear

The DCT front springs were higher than I liked (basically stock/OE height). The ZCP manual front spring is what I'm using right now. It's not much lower than stock, but gives me the front ride frequency I want and barely clears parking blocks.

In the rear the ZCP progressive spring wasn't very good for my setup. The initial rate ride frequency was too low, but the final rate was good. Because of the progressive nature and how mismatched the progressive travel was to my chassis it felt like I was dragging the rear end when doing hard cornering.

Forum member bariaga1 purchased a set of F80/82 DCT ZCP springs from me for his F30 335i M-Sport. They dropped his ride height 1/4" in the front, and rear (note that the M-sport already sits lower than base suspension cars). When we went for a test drive after installing the springs the ride felt pretty good, and I didn't feel the dragging sensation as with my car. Last I heard he was pleased with how much more nimble the car felt.


Other Springs

From the data/spec sheets I've seen it looks like Eibach's F3x front springs replicate F80/82 spring rates (within 5%). Eibach's 6cyl RWD/4cyl xDrive and 4cyl RWD front springs have about the same rate as F80/82 base suspension front springs, and Eibach's 6cyl xDrive front springs are about the same rate as ZCP fronts. The Eibach springs will lower the car more than the F80/82 springs though, with the exception of the "tall" 6cyl xDrive front spring (F11-20-031-06-VA), which should have pretty much the same height as an F80/82 DCT spring. Eibach has a spring rate tolerance of +/- 5%, and BMW's is tighter than that.


Please don't PM me about springs for your car, 1) so we can keep the info public to help others and 2) I'm not your personal spring consultant, unless you're buying one of the sets I have for sale , haha.

[Eschmacher]

Thanks for your hard work, Farkle. I'm in the process of obtaining a set of f80 springs. Much cheaper than the eibach springs I was going to go with originally. Also trying to pick the bumpstops I pair with them, probably going with the f80 ones as well, since it's less of a drop.

[BMW DIY Guy]

And this is why I love this forum.. the info is just amazing!

[dr.roro]

Wow great post! Do you happen to know the OEM spring rates (for F3x/F8x)?

[FaRKle!]

Originally Posted by BMW DIY Guy

First and foremost.. THANK you for such a great write up and it answered almost all of my questions.

I picked up a set of F80 springs from a fellow forum member and trying to decide what I have, and if I should put them into my car.

I have a 6MT F32 oem non adaptive suspension at 60k miles, and the springs I got are MB and MC according to your chart info.. so DCT and plain roof.

This sounds like a possible mismatch maybe?

I also get a creak sound about 1 time in 10 when I get out of the car, drivers side rear, sounds like a spring creak. My thought is this change would address that as well.

Thank you for any advice!

The F80 DCT front spring will still work on your car, but won't lower as much as a manual transmission spring (could be same ride height as now). You'll have to look at the weight difference of your car vs ZF 8HP 435i to gauge how much higher/lower it'll be. For the rear spring you can use shims on the spring cup like I have to raise the rear if you feel you need it.

You need to be careful with creaks/noises as lots of times they don't necessarily come from where you think they come from. Could be a spring, could be a bushing, or could be the arm/subframe mounts articulating. Try putting that corner of the car in the air and using a jack to articulate the suspension to see if you can replicate it.

Originally Posted by dr.roro

Wow great post! Do you happen to know the OEM spring rates (for F3x/F8x)?

See below taken from F80 section. The F80 base suspension rates, and ZCP front rate below fall within BMW's tolerance for DCT and manual transmission springs. The ZCP rear rate is on the high side of a sunroof car for the spring's final rate.

Originally Posted by MFNATIK

Well folks, here's the moment you've all been waiting for...drum roll please!

M3 (Civic)
Front - 177 lbs/in
Rear – 591 lbs/in

M3 (Comp. Pkg)
Front – 198 lbs/in
Rear – 685 lbs/in

Eibach Pro Kit
Front – 183 lbs/in
Rear – 628 lbs/in

[BMW DIY Guy]

So I read that is I am OK (not causing problems) to make this change to hopefully improve handling over stock.

F32 F35 non adaptive shocks, stock springs with a sunroof, going to MB/MC F80 springs.

Yes?

[FaRKle!]

Originally Posted by BMW DIY Guy

So I read that is I am OK (not causing problems) to make this change to hopefully improve handling over stock.

F32 F35 non adaptive shocks, stock springs with a sunroof, going to MB/MC F80 springs.

Yes?

It shouldn't cause any functional problems. It's the ride height where there's some uncertainty.

[BMW DIY Guy]

Side note: I apologize for PMing you on this, I just noticed your comment.

"Please don't PM me about springs for your car"

[BMW DIY Guy]

Originally Posted by FaRKle!

The F80 DCT front spring will still work on your car, but won't lower as much as a manual transmission spring (could be same ride height as now). You'll have to look at the weight difference of your car vs ZF 8HP 435i to gauge how much higher/lower it'll be. For the rear spring you can use shims on the spring cup like I have to raise the rear if you feel you need it.
.

Forgive me bumbling through this, suspension is not something I have messed with yet so trying to learn asap.

From what I see about weight, the 6MT (3494lbs) and auto (3527) are nearly identical, am I comparing the correct weights? I read the similar age M3 is 3439lbs, so slightly lighter.

[FaRKle!]

Originally Posted by BMW DIY Guy

Forgive me bumbling through this, suspension is not something I have messed with yet so trying to learn asap.

From what I see about weight, the 6MT (3494lbs) and auto (3527) are nearly identical, am I comparing the correct weights?

You need to think about the corner weights and the load on each spring. So take the vehicle weights, then the weight distribution to find the load on each axle, then divide that by two to get the weight on each spring/corner on that axle. If the weights are really close, then you don't really need to worry about much of a difference in ride height. If there's a large load difference, then you might want to try and calculate what that could be in terms of ride height by using Hooke's law (F=kx). You can use the F8x the spring rate stated previously (one spring rate you'll have to guess, but you can assume the 2-3% delta I stated in the original post).

Since the mfg tolerance ranges of the DCT and manual springs overlap (by a good amount too), it's possible to get a DCT spring that gives you the same rate and drop as a manual spring. Of course without testing your exact spring you wouldn't know the rate.

[BMW DIY Guy]

Ok.. lets see.. finding weight distribution wasn't quick that is for sure.

435i - 51.1% to the front and 3494lbs (6MT)

Front - 1785 (892 each side)
Rear - 1701 (854 each side)

F80 M3 - 52.2% to the front and 3596lbs (DCT)

Front - 1877 (938.5 each side)
Rear - 1719 (859.5 each side)

So the way I read this, the rears will be nearly identical, and the fronts could be slightly higher? Assuming the springs themselves coiled are the same height?

How did I do?

[FaRKle!]

Originally Posted by BMW DIY Guy

Ok.. lets see.. finding weight distribution wasn't quick that is for sure.

435i - 51.1% to the front and 3494lbs (6MT)

Front - 1785 (892 each side)
Rear - 1701 (854 each side)

F80 M3 - 52.2% to the front and 3596lbs (DCT)

Front - 1877 (938.5 each side)
Rear - 1719 (859.5 each side)

So the way I read this, the rears will be nearly identical, and the fronts could be slightly higher? Assuming the springs themselves coiled are the same height?

How did I do?

Sorry, I meant compare the weight difference between F32 8AT vs F32 6sp. From what I've calculated before there should be ~1/3" front drop from F32 8AT front springs to F80/82 DCT front springs, so whatever delta you calculate from F32 8AT to F32 6sp you can subtract from that 1/3".

[BMW DIY Guy]

Originally Posted by FaRKle!

Sorry, I meant compare the weight difference between F32 8AT vs F32 6sp. From what I've calculated before there should be ~1/3" front drop from F32 8AT front springs to F80/82 DCT front springs.

Ah ok.. but thank you for figuring that out, sounds like I am good to go once I make sure I have the right tools. Likely will do the work this weekend then.

[Jerich0]

Hello Guys,

Great work here...

Question about the ZCP DCT carbon roof springs... since they are progressive will this be the softest rear setup I can use?

How much stiffer did your cars get using F80 springs, especially on small bumps and cracks...

Thanks!

JC

[FaRKle!]

Originally Posted by Jerich0

Hello Guys,

Great work here...

Question about the ZCP DCT carbon roof springs... since they are progressive will this be the softest rear setup I can use?

How much stiffer did your cars get using F80 springs, especially on small bumps and cracks...

Thanks!

JC

The soft rate on the ZCP springs isn't too far off from the M-sport rate on some of the F3x vehicles. The travel on the soft rate isn't too much. Harshness over bumps/cracks is largely a function of dampers.

[Jerich0]

Thanks Farkle...

So which one will you choose if you are going for the softest setting?

[Gen13 F36]

According to your post... concerning ride height, I have 428i GC.. there is a possibility it will raise it more because the 428i GC lighter on the front.

Just one question, because this is a M springs means the highest height is the same as an M car. Will it raise the car because its lighter than an M car?

[FaRKle!]

Originally Posted by Jerich0

Thanks Farkle...

So which one will you choose if you are going for the softest setting?

I'm not sure what exactly you're trying to accomplish. You want softer springs than OE, you want the softest M3/4 springs, or something else?

Originally Posted by Gen13 F36

Just one question, because this is a M springs means the highest height is the same as an M car. Will it raise the car because its lighter than an M car?

Not necessarily because the height of the lower spring perches probably differs on M-cars. You really have to do ride height calcs relative to your OE springs.

[Jerich0]

Originally Posted by FaRKle!

I'm not sure what exactly you're trying to accomplish. You want softer springs than OE, you want the softest M3/4 springs, or something else?




Not necessarily because the height of the lower spring perches probably differs on M-cars. You really have to do ride height calcs relative to your OE springs.

Im looking for the softest F80 rear spring, at least initially.

Thanks!
JC

[FaRKle!]

Originally Posted by Jerich0

Im looking for the softest F80 rear spring, at least initially.

Thanks!
JC

The soft rate on the ZCP rear spring is softer than the non-ZCP spring.

[cart75]

I have a F30 335 xdrive auto and l have a set of f80 dct mb springs how much lower would it be with these springs right now l have H&R springs with a set of B6 rides firm but big bumps are not nice.

[Jerich0]

How much harsher did your ride get with F80 springs?