BMW M2/M3/M4 Suspension Deep Dive!

[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

[dvq]

Excellent information as usual. The measured motion ratio is probably slightly different on the F80/F82 right? I've been meaning to go and measure it all myself but dealing with an injury preventing me from doing so right now.

I've been watching a few of FCM's videos and researching all of the different concepts yet but it hasn't all clicked for me quite yet. Waiting for it to make sense before I really make any suspension changes.

Was really surprised by the lack of travel before engaging the bumpstops — explains the very low spring rate up front for this car and the stiff progressive bumpstops.

[chrisjguzman]

[FaRKle!]

Originally Posted by dvq

The measured motion ratio is probably slightly different on the F80/F82 right?

The subframes, control arms, knuckles/wheel carriers are common between the F87 and F80/82/83 so the motion ratios are the same.

Originally Posted by dvq

I've been watching a few of FCM's videos and researching all of the different concepts yet but it hasn't all clicked for me quite yet. Waiting for it to make sense before I really make any suspension changes.

I've spent A LOT of time (and going through many configs) validating the trends FCM professes both on and off the track before I bought in, and I have to say Shaikh's been right. It's been very illuminating going from pitch, to slightly flat ride, to higher flat ride ratios and seeing how the car responds on specific corners at the track, how the smoothness in daily driving is impacted, and how going from rebound biased to compression biased really supports and helps the car get less upset over uneven surfaces (from curbing/alligators teeth to offroad).

[dvq]

Originally Posted by FaRKle!

The subframes, control arms, knuckles/wheel carriers are common between the F87 and F80/82/83 so the motion ratios are the same.

Awesome, that would be the first time I've seen anyone on the F80 forum ACTUALLY measured the motion ratios then. Lots of estimates, control arm measurements, and incorrect numbers from Ohlins being quoted.

Front Spring/Damper: 0.95 (Mentioned in the second video)
Rear Damper: 0.76 (Mentioned in the second video)
Rear Spring: 0.58 (Measured in the first video, but is this correct?)

[BWT]

Originally Posted by FaRKle!

The subframes, control arms, knuckles/wheel carriers are common between the F87 and F80/82/83 so the motion ratios are the same.



I've spent A LOT of time (and going through many configs) validating the trends FCM professes both on and off the track before I bought in, and I have to say Shaikh's been right. It's been very illuminating going from pitch, to slightly flat ride, to higher flat ride ratios and seeing how the car responds on specific corners at the track, how the smoothness in daily driving is impacted, and how going from rebound biased to compression biased really supports and helps the car get less upset over uneven surfaces (from curbing/alligators teeth to offroad).

Thanks for the useful information.

For registration purposes in Australia, the requirement is that at least two thirds of the original suspension travel should be maintained in both directions (extension and compression) if a car is lowered. My car is an F80 M3 Competition, would you know if this requirement would be met if I lowered the car 20mm front and 5-10mm rear using these Eibach springs?

https://eibach.com/us/c-178-product-...bmw-m3-m4.html

Many thanks in advance.