[FaRKle!]

I thought it'd be fun to take a deep dive into the suspension on the M2/M3/M4. In the videos below I show you the design, layout, and some measurements of the F8x architecture. Additionally, Fat Cat Motorsports was kind enough to lend their expertise on our suspensions and measured the springs, bump stops, sway bars, and dampers (part 2).

Originally Posted by Index

-0:00 Intro
-0:28 Ride height
-1:15 Under the hood design
-2:59 Front strut/spring assembly
-6:05 Front endlinks, sway bar, and control arms
-9:04 More front strut
-9:53 Rear control arms layout
-12:10 Rear alignment adjustments
-14:29 Rear damper and spring
-16:24 Rear sway bar

Originally Posted by Index

-0:00 Intro
-0:26 Motion ratios
-2:10 Bump stops
-6:24 Springs
-8:03 Ride frequencies
-8:40 Damper dynos
-10:38 Sway bars

[NISFAN]

Awesome, thank you for adding technical detail on a level rarely seen. Explains a lot about the standard BMW M car setup.

[M Fifty]

Debate about component naming conventions in 3...2...

[M2C_PLUS]

Originally Posted by M Fifty

Debate about component naming conventions in 3...2...

: :

[H20neun]

thanks! I was surprised that the space between shock and bump stop is so small

even if people cut the bump stop or use shorter ones, I am pretty sure that heavily lowered car often do have no space between shock and bump stop at all!
ride quality must suffer from that..

[FaRKle!]

Originally Posted by H20neun

thanks! I was surprised that the space between shock and bump stop is so small

even if people cut the bump stop or use shorter ones, I am pretty sure that heavily lowered car often do have no space between shock and bump stop at all!
ride quality must suffer from that..

Absolutely! This is why I'm such a big proponent of either getting or cutting bump stops when using lowering springs. It's pretty common for cars to be resting on their bump stops at static ride height if they don't do that.

It also applies to coilover kits too. If you take a B16 set and run it near the lower ride height vs higher you can feel the ride quality change due to the bump stop engagement.

[chief1richard]

Originally Posted by FaRKle!

Absolutely! This is why I'm such a big proponent of either getting or cutting bump stops when using lowering springs. It's pretty common for cars to be resting on their bump stops at static ride height if they don't do that.

It also applies to coilover kits too. If you take a B16 set and run it near the lower ride height vs higher you can feel the ride quality change due to the bump stop engagement.

Would you know what the OEM ride height is for 18" wheels. Measured from bottom of wheel to top fender lip.

[FaRKle!]

Originally Posted by chief1richard

Would you know what the OEM ride height is for 18" wheels. Measured from bottom of wheel to top fender lip.

It'll be fender to center of hub measurement plus the radius of the wheel.

You know the fender to center of hub measurement from my video. Then add the radius of an 18" wheel to that.

[chief1richard]

Originally Posted by FaRKle!

It'll be fender to center of hub measurement plus the radius of the wheel.

You know the fender to center of hub measurement from my video. Then add the radius of an 18" wheel to that.

Unfortunately I did not take a measurement before I started my suspension job. I have no reference point now. I'm trying to lower 10mm from OEM with my Ohlins. Would you know what the OEM measurement is?

[M Fifty]

Maybe just go with the MPS settings? So 595mm front/600mm rear (19") or 574mm front/579mm rear (18")

Both measured from bottom of wheel to top fender lip.

HTH

[chief1richard]

Originally Posted by M Fifty

Maybe just go with the MPS settings? So 595mm front/600mm rear (19") or 574mm front/579mm rear (18")

Both measured from bottom of wheel to top fender lip.

HTH

Delete

[chief1richard]

Originally Posted by M Fifty

Maybe just go with the MPS settings? So 595mm front/600mm rear (19") or 574mm front/579mm rear (18")

Both measured from bottom of wheel to top fender lip.

HTH

I would do that but my suspension recommends 10mm drop from OEM. I am not looking for more than that. Ohlins kit I have does not lower as much as others for optimum performance, which is what I am after, not aesthetics.

[M Fifty]

Well - to be clear - if aesthetics were the main reason for replacing the stock suspension I could have spent a lot less than the cost of the MPS.

it offers a 20mm drop over standard, so a little arithmetic should see you on your way.

But. The Ohlins - surely - offers independent adjustment of ride height and spring preload for a given spring rate? So, perhaps you could explain how the damper is only good for up to 10mm of ride height change. It seems to defeat the object.

Hope you eventually find what ever it is you're looking for.

[BMW DIY Guy]

Absolutely stellar information thank you!

In regards to sway bars: What I heard was rears are not worth changing, as the load is so minimal. For the fronts, I was incredibly pleased (as I am in the middle of a crank hub change) to see the front is SO incredibly easy to change.

Is it worth it to change the front?

I know that is a subjective question as the answer depends on usage model, which for me is 99% daily driver, 1% rare driving day, maybe track (some day) club driving event type of model.

I am just stunned on how easy (by comparison to the front and rears I did on my F32) it would be to change the front.

[MR RIZK]

FaRKle! regarding the rear motion ratio of 0.76. In the video it is stated as 0.76 to the damper. What was the ratio to the spring?

Btw thanks for the videos!

I think for part 3 you should go further in-depth how the rear motion ratio will be affecting your suspension choice since you have provided some info around the dyno graphs and wheel frequencies. Hint hint.

[FaRKle!]

Originally Posted by MR RIZK

FaRKle! regarding the rear motion ratio of 0.76. In the video it is stated as 0.76 to the damper. What was the ratio to the spring?

Btw thanks for the videos!

I think for part 3 you should go further in-depth how the rear motion ratio will be affecting your suspension choice since you have provided some info around the dyno graphs and wheel frequencies. Hint hint.

The spring motion ratio is 0.6375, so wheel rate is 0.406 of the actual spring rate.

Thanks for the suggestion for part 3! I'm sure I'll tie that into how I choose my spring rates for my bespoke FCM suspension (or maybe even an intermediate one...).

[Whatleytom]

edit: ignore

[BMW DIY Guy]

Originally Posted by FaRKle!

The spring motion ratio is 0.6375, so wheel rate is 0.406 of the actual spring rate.

Thanks for the suggestion for part 3! I'm sure I'll tie that into how I choose my spring rates for my bespoke FCM suspension (or maybe even an intermediate one...).

As always FaRKle! you are killing it thank you! I am excited on how easy it is to swap the M2C front sway bar, but the question is SHOULD it be done?

With all of your analysis, is it worth it in general?

Thanks as always for your analysis!

[n8dgr84]

This is super interesting nerd shit.
Thanks for sharing!

Would love to hear about your formulas and results.

[mr_lab_rat]

This is incredible, I learned so much!

For part 3 I would be curious to see an analysis of what stiffer springs (while keeping the stock dampers) do, mainly going from progressive to linear.

[M Fifty]

Originally Posted by FaRKle!

I thought it'd be fun to take a deep dive into the suspension on the M2/M3/M4. In the videos below I show you the design, layout, and some measurements of the F8x architecture. Additionally, Fat Cat Motorsports was kind enough to lend their expertise on our suspensions and measured the springs, bump stops, sway bars, and dampers (part 2).

Well, a Wind Sock isn't going to fix the sound on Part 2, but maybe a FIM-92 Stinger?

[M Fifty]

Noting that there is always variability between dyno's (which is why you should always do Before:After on the same setup), JetBill's findings for comparison:

https://f87.bimmerpost.com/forums/sh...31&postcount=1