BMW M3 Forum
BMW M3 Forum BMW M3 Gallery BMW M3 Reviews BMW M3 Social Groups BMW M3 Chat M3Forum Sponsors >>
Loading


Mobile M3forum
Go Back   BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X) > BMW M3 Discussions > E46 M3 (2001-2006)
Tire Rack Buy Winter Tires Now!
Not a member? Register Now!
Register Gallery All Albums Garage Search Today's Posts Mark Forums Read Calendar FAQ

E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


Reply
 
Thread Tools Display Modes
Old Mon, Sep-17-2018, 12:37:35 AM   #1
ShaikhA
Fat Cat Motorsports
 
Join Date: Sep 2015
Posts: 147
Reputation: 0 ShaikhA is on a distinguished road
Location: Redwood City

United States




Default FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffness)

I created this 'Ride Harmonizer' suspension spreadsheet for the E46 M3 community to use as a way to numerically understand changes to their M3's handling behavior based on key suspension components such as the sway bars, spring rates, and bump stops. The general vehicle inputs are at the bottom of the sheet - items like vehicle weight, driver / passenger weight, tire and wheel weight, and front weight distribution (in case you've lightened the car enough to change that from factory). Or you can leave the general vehicle inputs at the default which are pre-filled for the E46 M3 coupe.




Then, in the top section under 'FRONT and REAR tubular or Solid Sway Bar inputs' you can enter front and rear sway bar OD/thickness, front and rear spring rates, and front and rear bump stop rates (if you know them). I've already created a few lines with info you can examine so see how the factory suspension behaves in terms of the bounce frequencies (which does create Flat Ride), the Front Roll Couple %, and the roll stiffness.

I'll describe these terms later but for now, I want to express my strong recommendation that you use this sheet to a) check that any spring rate change you make maintain at least a few percent rear-biased in the bounce frequencies which creates 'Flat Ride' and b) you keep the FRC in a range near the factory so you don't create excessive oversteer (too low FRC) or understeer (too high FRC).

For part a), the rear bounce frequency should be higher than the front bounce frequency, often by 10% or so. The spreadsheet will indicate FLAT RIDE when that's the case. There's different degrees of Flat Ride but I consider 10-15% a minimum for a softer-sprung BMW and 3-5% for a race M3. The factory M3 suspension comes with about 17% rear Flat Ride bias!

For part b), the choice of spring rates will work together with the sway bar diameter to create the FRC % and keep the car's handling neutral, or appropriately biased to your level of power modifications. A higher-output engine would benefit from a higher front roll couple to keep the car neutral once throttle is applied.

In some cases, you may only want to use an upgraded front bar, instead of a 'matched front and rear set' or potentially remove the rear bar, or make other complementary changes. But by first focusing on creating Flat Ride and then aiming for a neutral FRC, you'll keep your BMW in a more optimal ride quality and handling zone. And yes, Flat Ride even applies to hardcore track setups, as I've tested and proven for my 330i and several M3s of various generations.

===

If you want to go deeper into using the sheet, you can make more use of the various sections.

Do keep in mind is that ride height / roll centers / center of gravity are NOT considered in this analysis - I assume you are keeping these variable constant and changing spring rates, sway bar diameter / arm length, and potentially looking at bump stop contributions. Getting the proper ride height is an important question and usually you don't want to 'dump' the car and expect everything to be shiny.

'Why Flat Ride Matters'

For those who want a more thorough discussion on how to use the sheet, refer to this video.

'How to use the FCM Elite Ride Harmonizer FRC and Setup Evaluation spreadsheet'

===

There are general vehicle inputs at the very bottom of the screen, then each of the three sections has some unique inputs for more refined calculations. The various parts of the spreadsheet are:

Section 1, for front and rear tubular or solid sway bars - For inputs, you would enter the front and rear sway bar outside diameter and wall thickness (if tubular, otherwise make that 1/2 the diameter for a solid bar). Enter the spring rates and bump stop rates if you know them or want to guess (typically a factory front is about 200 lb/in and rear is about 100 lb/in. This is also partly why our cars tend toward understeer in hard cornering due to the higher rate and longer length front bump stop. The sway bar arm dimensions come from the inputs at the very bottom of the spreadsheet.

You will see outputs for the bounce frequency (or ride frequency), whether you have FLAT RIDE or PITCH (you want Flat Ride!), what the front roll couple percent is (FRC%), the total roll stiffness as well as distribution between front and rear, and how much comes from sway bars vs. springs. The front roll couple % is a useful metric that indicates how much weight transfer occurs across the front wheels as a percent of the total weight transfer. The lower the number, the more weight you have going across the rear wheels and the more oversteer you'll experience. I find that ~70-74% is a good range for an E46, with an M3 being driven hard potentially needing a few percent higher FRC so you can use the throttle more aggressively on corner exit.

Section 2, for adjustable sway bar arm length - You can enter different hole positions for both front and rear bars to see how the FRC changes. Useful to get a sense of the range of adjustment you have available on your setup. Keep in mind that packers / bump stop spacers are quick and easy ways to make balance changes, as well as spring rubbers which are like bump stops 'donuts' that fit between the spring coils!

Section 3, Racer's Edge - Here you can enter corner weights and spring rate at each corner and see the resulting ride frequency. Yeah, pretty cool right?! Some of you may know that weights can differ noticeably especially once you've done some lightening. I'm actually using different springs between left front and right front, and left rear vs. right rear. My friend Peter, who was user 'pyce' on VWVortexforum many moons ago, introduced me to the idea that VW had many different spring available based on model and option package. They took their ride frequency selection very seriously! Granted, if it's less than 0.1-0.2 Hz different between left and right you're likely not going to notice that, but it's worth checking out if you have corner weight data or any weight addition/reduction that could impact the overall weight balance. It sure did in my case!

===

Okay, all well and good but how about some examples of how it could help you? Here are 4 I can quickly think of:

Example 1: I tested some E46 H&R 'Race' lowering springs, which I'm not generally a fan of but I wanted to see how they worked. I estimated the spring rate (via # of coils / coil thickness / approximate coil ID method) and found that the front was about 300 lb/in (when loaded) but the rear was around 500 lb/in. That's the 3rd line down in Section 1 of the spreadsheet (you can see this in the middle-right side of the above image).

This 300/500 spring rate combination would have resulted in a lower rear frequency than front, causing pitch. I know pitch sucks - the factory springs provide Flat Ride so why would I screw that up!? - and didn't want to make problems for myself. So, I bought the Ground Control rear weight jacker and played with the spreadsheet to find a spring rate that would create about a 10% higher rear frequency. That ended up being a 650 lb/in. This combo is the 4th line down, below the 300/500 H&R combo. I installed that rear 650 lb/in rear spring w/GC jacker plus the H&R Race front spring and really enjoyed the way the car rode and performed! It would have NOT felt or handled as well with the standard H&R Race rear.

Example 2: MANY coilover setups use softer-than-optimal rear springs. This can work 'okay' for smoother tracks that aren't exciting the car very much, but there is always a subtle (or not so subtle, depending on the damper tuning) oscillation / bouncing occurring. A TC Kline setup with their standard 400/700 is *close* to Flat Ride, but I calculate the front frequency being a little higher than the rear. A stiffer rear would help the car 'smooth out' faster over bumps/dips/track or road imperfections.

Example 3: I've worked with more E36 M3s than I have E46 M3s, especially for dual-purpose street and track use, along with dedicated NASA ST3/ST4 race use. The spring rates I came up with on a few of those setups (to give at least a few percent rear bias for some Flat Ride) were 425 front and 700 rear. The drivers had great praise for how our Elite setups worked, and one (Percy, NASA racer in the SF Bay Area) said it was smoother than he expected on the street while working far better than the TC Kline D/As he took off the car to put ours on.

Example 4: I'll discuss this in more detail in the F80 section, but I spent a good bit of time doing consulting for an enthusiast going between KW Clubsport and Bilstein PSS10. He'd been following my Suspension Truth Youtube channel for a while and was familiar with the concept and application of Flat Ride. He didn't like how either setup worked with the standard springs and sought my help to pick different spring rates. Due to availability, he had limited options to begin with, but each step we took to get the front a little softer and the rear a bit firmer made the ride better - at the same or even SOFTER damper settings! His comments are below, once he could really experience Flat Ride:

---

---

His F80 spring rate changes were a very revealing experiment and he's much happier now with Flat Ride than he was at the start. He's also got 2 young boys and a wife he's concerned about bouncing around unnecessarily, so it's not just about performance (which he says it even better and more consistent than before) but about the ride quality benefits from Flat Ride. He did add a bigger front bar while keeping the rear stock, as I recommended so the FRC would stay in a neutral (~70%) range.

===

In summary, I've found this spreadsheet and the concepts I apply in it to be extremely useful and I know it'll be a benefit to this community. I'll be very happy to see more people asking about / thinking about ride frequencies when picking setups or changing springs. Ask your vendors 'what are the bounce frequencies of this setup you're selling?' They NEED to know! Because you'll be IMPACTED by what they design in, whether intentionally or by accident. I want to encourage more discussion and utilization of concepts like Flat Ride vs. pitch.

At a deeper level, the damper's behavior is absolutely critical but that's another topic for another time (and another spreadsheet!). Understanding concepts like 'jacking down' (i.e. excessive rebound damping vs. compression damping) and the impact of damper gas pressure make a big difference to help select / modify suspension components that achieve your goals with the least negative impact. To me, that means minimizing ride harshness / passenger discomfort / instability for emergency situations or inclement weather while maximizing grip, control, and confidence. It's why I call this the 'Ride Harmonizer' spreadsheet as it helps point you toward a really well-dialed setup.

P.S. I do already have a free sheet for damping calculations and analysis but it's a bit busy and I'm not sure how many people would be ready / able to use it unless I cleaned it up a bit. If someone is interested in access to that, PM me and I'll send you the link and the 'how-to' video I made for it.
__________________


FCM Elite Ride Harmony suspension spreadsheet for: E46 M3, Shock dyno testing / driving feedback: E46 M3 (with Eric_SMG)

Take our short Ride Harmony survey and earn a credit on FCM Elite Bilstein damper services
Jump to top ShaikhA is offline   Reply With Quote
Sponsored Links
Register now and remove these ads
Old Mon, Sep-17-2018, 03:25:29 AM   #2
whips333
Registered User
 
whips333's Avatar
 
Join Date: Jun 2009
Posts: 854
In the garage:
Reputation: 0 whips333 is on a distinguished road
Location: New Britain

United States




Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

Sub'd
Jump to top whips333 is offline   Reply With Quote
Old Mon, Sep-17-2018, 02:14:51 PM   #3
Obioban
Moderator
 
Obioban's Avatar
 
Join Date: Jul 2003
Posts: 36,459
In the garage:
Reputation: 54 Obioban has a spectacular aura about
Location: SE PA

United States




Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

excellent!

... I wish we had stifness data on the stock CSL sway bars, with their variable thickness-- no idea how to enter those.
__________________

Current Cars: 2005 IR/IR M3, 2001 LMB/blk M5, 03 530i, 04 M3 wagon, and some boring stuff
Past cars: 04 M3, 96 M3, S50B32 e36 M3 CM race car
Jump to top Obioban is offline   Reply With Quote
Old Mon, Sep-17-2018, 10:07:20 PM   #4
ShaikhA
Fat Cat Motorsports
 
Join Date: Sep 2015
Posts: 147
Reputation: 0 ShaikhA is on a distinguished road
Location: Redwood City

United States




Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

Cheers, Obioban! Do you have a link to threads with more info? I'm not sure how much the thickness varies but it's not likely to make a difference of more than 1-2% FRC. If you have an average thickness to use then just plug that in and change other variables like springs and bump stops.

The spreadsheet is intended for semi-quantitative comparisons between different setups, so if you're making a change it'll help you predict how the handling (FRC), ride quality (bounce frequencies), overall stiffness (roll stiffness) will change.
__________________


FCM Elite Ride Harmony suspension spreadsheet for: E46 M3, Shock dyno testing / driving feedback: E46 M3 (with Eric_SMG)

Take our short Ride Harmony survey and earn a credit on FCM Elite Bilstein damper services
Jump to top ShaikhA is offline   Reply With Quote
Old Mon, Sep-17-2018, 10:34:51 PM   #5
M spec
Rembrandt Audio
 
Join Date: Jan 2018
Posts: 672
Reputation: 0 M spec is on a distinguished road
Location: Irvine, CA

Austria




Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

Does FCM have re-valved Bilstiens for sale for our cars?
Jump to top M spec is online now   Reply With Quote
Old Mon, Sep-17-2018, 10:47:15 PM   #6
Obioban
Moderator
 
Obioban's Avatar
 
Join Date: Jul 2003
Posts: 36,459
In the garage:
Reputation: 54 Obioban has a spectacular aura about
Location: SE PA

United States




Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

Quote:
Originally Posted by ShaikhA View Post
Cheers, Obioban! Do you have a link to threads with more info? I'm not sure how much the thickness varies but it's not likely to make a difference of more than 1-2% FRC. If you have an average thickness to use then just plug that in and change other variables like springs and bump stops.

The spreadsheet is intended for semi-quantitative comparisons between different setups, so if you're making a change it'll help you predict how the handling (FRC), ride quality (bounce frequencies), overall stiffness (roll stiffness) will change.
CSL front is 30.8mm but "hollow" (how hollow unknown).

CSL rear is 22.5mm solid, but isn't changes shape a bit depending on location. My assumption is that it acts, on average, like a 22.5mm bar.

I suppose we could make an educated guess at how hollow it is by comparing the weight to the weird of the smaller ID/solid stock sway, which would probably be ~good enough since the center of the bar doesn't contribute that much...

Quote:
Originally Posted by M spec View Post
Does FCM have re-valved Bilstiens for sale for our cars?
Yes. EricSMG posted a review of them a while back.
__________________

Current Cars: 2005 IR/IR M3, 2001 LMB/blk M5, 03 530i, 04 M3 wagon, and some boring stuff
Past cars: 04 M3, 96 M3, S50B32 e36 M3 CM race car
Jump to top Obioban is offline   Reply With Quote
Old Mon, Sep-17-2018, 11:43:01 PM   #7
M3 dude
Registered User
 
Join Date: Jan 2014
Posts: 393
Reputation: 0 M3 dude is on a distinguished road

Australia




Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

thanks for making this!

the dilemma i have going on in my head is that this flat ride concept is sound. makes sense.
however, any time we talk about spring rates for the e46 m3 to be driven in anger, the 100 lb/in split fr / rr is used (eg 500/600, 700/800 etc).

any way you cut it, this won't achieve flat ride. what's the story there?
Jump to top M3 dude is online now   Reply With Quote
Old Tue, Sep-18-2018, 01:08:53 AM   #8
M spec
Rembrandt Audio
 
Join Date: Jan 2018
Posts: 672
Reputation: 0 M spec is on a distinguished road
Location: Irvine, CA

Austria




Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

Quote:
Originally Posted by Obioban View Post
CSL front is 30.8mm but "hollow" (how hollow unknown).

CSL rear is 22.5mm solid, but isn't changes shape a bit depending on location. My assumption is that it acts, on average, like a 22.5mm bar.

I suppose we could make an educated guess at how hollow it is by comparing the weight to the weird of the smaller ID/solid stock sway, which would probably be ~good enough since the center of the bar doesn't contribute that much...



Yes. EricSMG posted a review of them a while back.
Searched, but couldn't find it, have the link handy by chance?
Jump to top M spec is online now   Reply With Quote
Old Tue, Sep-18-2018, 01:34:00 AM   #9
Volke
Registered User
 
Join Date: May 2017
Posts: 268
Reputation: 0 Volke is on a distinguished road
Location: Chicago

United States




Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

Nice work!

There's a small part you got wrong though. A race M3 should have a higher frequency up front unless you're on a really bumpy track. It allows for faster response on corner entry, less ride height variation up front(especially with front aero which is more pitch sensitive) and gives better rear wheel traction for corner exit. It does come with a less comfortable ride penalty though.

The reason street cars have a higher rear frequency is because it makes the ride more comfortable when going over bumps by allowing the front and rear suspension to absorb the bump in unison.
__________________
Peter
Mechanical Engineer

Last edited by Volke; Tue, Sep-18-2018 at 01:46:58 AM.
Jump to top Volke is offline   Reply With Quote
Old Tue, Sep-18-2018, 01:50:11 AM   #10
Obioban
Moderator
 
Obioban's Avatar
 
Join Date: Jul 2003
Posts: 36,459
In the garage:
Reputation: 54 Obioban has a spectacular aura about
Location: SE PA

United States




Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

Quote:
Originally Posted by M spec View Post
Searched, but couldn't find it, have the link handy by chance?
http://www.m3forum.net/m3forum/showthread.php?t=534318
__________________

Current Cars: 2005 IR/IR M3, 2001 LMB/blk M5, 03 530i, 04 M3 wagon, and some boring stuff
Past cars: 04 M3, 96 M3, S50B32 e36 M3 CM race car
Jump to top Obioban is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



All times are GMT. The time now is 04:37:48 AM.


Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
M3Forum.com and M3forum.net is in no way sponsored, endorsed or affiliated by or with BMW NA / BMW AG or any of it's subsidiaries or vendors.
BMW and M3 (E90 M3 | E92 M3 | E93 M3 | E46 M3 | E36 M3 | E30 M3) are registered trademarks of BMW AG.
M3Forum Terms of Service
Copyright 1999-2017 M3Forum.com
Discussing FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffness) in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)