e46 M3 suspension setup, or how to not downgrade your car with suspension mods

[SQ13]

My current ratio is 1.05 - 1.87F/1.96R Hz (336/628 lb/in). Target speed ends up being 155 MPH lol. Even if I switch to 700 lb/in springs, that puts me at 95 MPH. Booooo

[LSB4Me]

Maybe it's the bad LA roads, not sure. Moving back to a 350/500 setup completely eliminated the oscillating rear, but I felt the front end needed to be stiffer.

We are in the same boat. It's definitely our roads.

I have been chasing a comfortable, OEM+ setup on with my Ohlins RT setup on LA roads for 6 months. Funny, like you I found that moving to 500 (9kg / 504lb, to be exact) in the rear also stopped my oscillation problem. With 9kg springs out back, I have a rear that is more composed and less prone to bobbling over each and every one of the many road imperfections in LA. To be clear, my car has and will never see the track, so I don't care about anything other than attaining a comfortable ride with a reasonable ride height that doesn't scrape in/out of every transition in our not-so-flat city.

I have learned a few interesting things worth sharing along the way: (1) Ohlins says that their pressurized struts add to the effective spring rate thereby making the car stiffer than the stated spring rates--Koni struts can be compressed by (strong) hands, Ohlins require 70ish pounds of pressure to compress; and (2) Ohlins increased their spring rates at least on the e9x platform to create a v2 kit after receiving complaints that their setup was too soft--read, more road-focused than track-focused. The latter point was a bit of an "ah-hah" moment for me as the RT kit I had on my e9x many years ago was simply sublime. I have come to realize that I had their v1 (softer) kit and, thus, I began moving down in spring rates on my e46.

You are more than welcome to come drive my setup, if it will help you on your journey. I've found that the Rose Bowl loop is a pretty good testing ground for suspension setups, given the broken pavement and undulations.

[duracellttu]

If you're dropping the front spring rate, you need a commensurate increase in sway bar rate to keep handling neutral. For a street car, you'll want to target your pitch balanced speed to a common speed you drive (35-70mph is a good range) and for a track car you'll want to target your average track speed (80-120mph or so). It's not binary.

Everything is subjective of course, and perhaps your setup with high front ride frequency really is faster for you in the canyons, but I'd $5 bet that it's not (if you're high enough in front) . The place where a higher front ride frequency really helps is if you're eating up all of your travel with mid corner bumps. Other than that, your car will maintain a more stable contact patch if your chassis is pitch balanced.

My car is setup for the street, and to my feel a front higher ride frequency is both a bit slower and also feels 'soggy' in the rear as the rear bounces higher and longer on road interruptions. The rear is more sensitive to camber change than the front, so this should be relatively more upsetting if not balanced with the front. The math is consistent with my experience setting up here for me personally.

All this said to counter your point for future readers that flat ride is for track cars only. It's for all cars, just set your pitch balanced speed, ride height and roll rate balance appropriately based on how/where you're driving.

edit: why are you targeting such high ride rates for an OEM+ setup? Are you running big 200 tread wear tires on the street and running out of travel in corners? Softer springs should be faster, especially on the street, if you're setting everything up right.

For those who are working solely off of the flatride spreadsheet and aiming for target ride frequencies of F 1.92 / R 2.05 which FCM considers a “sport” setting, this results in a 1.07 bounce frequency ratio, 74% FRC, and achieves flat ride. Those same F & R frequencies also give you a 125mph target road speed. From your point, that is much too high to be comfortable on the street, so it should target ~55-60mph. To achieve this, assuming you keep the same rear freq of 2.05, you need to lower the front spring rate to ~300# which give you a 1.18 bounce frequency ratio (close to stock). So I agree that it flat ride can be tuned for street setups. However, it is my option that when doing so and lowering the front spring rate down to even 336# to front end wasnt firm enough. YMMV.

All that to say, is that every setups will have trade offs. I've gone through lots of trial and error to come to the conclusions discussed and others are going through the same journey. Based on my experience TCK's recommend spring rates are pretty spot on for those who want an OEM+ street feel and aren't lying to themselves about how often they go to they go to the track.

[Bry5on]

My journey for a OEM+ comfortable street setup continues. As you mentioned my attempt at using 350/700 on the TCK SA didn't work out. After reaching out to TC he told me that the SA damper limit was a 700# spring, but didn't have enough compression to be good and recommended a DA. I didn't want to go that route so I opted for a FCM custom setup. Even with those dampers I wasn't getting a comfortable ride with a 700#. I've attempted to get flat ride to work on my street car with little success. Maybe it's the bad LA roads, not sure. Moving back to a 350/500 setup completely eliminated the oscillating rear, but I felt the front end needed to be stiffer.

That being said, my current setup is 400/600 but I don't have much seat time since I'm doing some new engine and tune upgrades. TC's recommendation for “great balance” is 400/500 on a street car. After all the experimenting, I agree that most would be happy with that setup. If you want stiffer, TC recommended 400/700. TBoneM3 has a lot of good suspension info on his journal page, which I've been following. He has gone down this same path we are discussing.

IMO flat ride should only be considered for track cars. It has proven results and many members really like it. Some might argue otherwise, but for me it wasn't providing the street solution I was looking for. Hope this helps.

If you’re dropping the front spring rate, you need a commensurate increase in sway bar rate to keep handling neutral. For a street car, you’ll want to target your pitch balanced speed to a common speed you drive (35-70mph is a good range) and for a track car you’ll want to target your average track speed (80-120mph or so). It’s not binary.

Everything is subjective of course, and perhaps your setup with high front ride frequency really is faster for you in the canyons, but I’d $5 bet that it’s not (if you’re high enough in front) . The place where a higher front ride frequency really helps is if you’re eating up all of your travel with mid corner bumps. Other than that, your car will maintain a more stable contact patch if your chassis is pitch balanced.

My car is setup for the street, and to my feel a front higher ride frequency is both a bit slower and also feels ‘soggy’ in the rear as the rear bounces higher and longer on road interruptions. The rear is more sensitive to camber change than the front, so this should be relatively more upsetting if not balanced with the front. The math is consistent with my experience setting up here for me personally.

All this said to counter your point for future readers that flat ride is for track cars only. It’s for all cars, just set your pitch balanced speed, ride height and roll rate balance appropriately based on how/where you’re driving.

edit: why are you targeting such high ride rates for an OEM+ setup? Are you running big 200 tread wear tires on the street and running out of travel in corners? Softer springs should be faster, especially on the street, if you’re setting everything up right.

[duracellttu]

duracellttu
Been reading and learning about flat ride all weekend. Just finished all 25 pages here among others.
You seem to have gone down a very similar path and asked the same questions I have had going through all of it.

Bought a set of TCK D/A with 400/500 as recommended by Mr. Kline. Is a dedicated track car that sees some backup-daily usage. 3350lb no driver. 50% corner balanced. Looking into flat ride info and had a few questions about your journey.

I see you went down the path of TCK S/A with ~350 and ~700. Said it was pretty bumpy? Did some adjustments and didn't really hear if it helped? Think you even debated getting D/A rears it seems.
You also inquired about why TCK recommended the 400/500 to you (My setup). Without much further forum discussion. Just trying to see what angle he has vs the flat ride mentality. If you ever maybe discussed that elsewhere.

Curious where you landed after all this time. Did you get the original 350/700 setup to work?
Did you end up happy with the outcome after doing flat ride on the tck?

Just looking for some tips. Literally just did my corner balance and yearly alignment last month. Kinda wish I had learned all this before that! lol. My car has felt great the last few track days but now this has me intrigued.

My journey for a OEM+ comfortable street setup continues. As you mentioned my attempt at using 350/700 on the TCK SA didn't work out. After reaching out to TC he told me that the SA damper limit was a 700# spring, but didn't have enough compression to be good and recommended a DA. I didn't want to go that route so I opted for a FCM custom setup. Even with those dampers I wasn't getting a comfortable ride with a 700#. I've attempted to get flat ride to work on my street car with little success. Maybe it's the bad LA roads, not sure. Moving back to a 350/500 setup completely eliminated the oscillating rear, but I felt the front end needed to be stiffer.

That being said, my current setup is 400/600 but I don't have much seat time since I'm doing some new engine and tune upgrades. TC's recommendation for “great balance” is 400/500 on a street car. After all the experimenting, I agree that most would be happy with that setup. If you want stiffer, TC recommended 400/700. TBoneM3 has a lot of good suspension info on his journal page, which I've been following. He has gone down this same path we are discussing.

IMO flat ride should only be considered for track cars. It has proven results and many members really like it. Some might argue otherwise, but for me it wasn't providing the street solution I was looking for. Hope this helps.

[STAATS]

Well let’s give it another shot then. Weird.

CG location change_332it.xlsx

edit: I think I managed to fix the original post too. Hopefully.

There it is!

Most appreciated

[Bry5on]

Hmm I am definitely missing something then... I can see the spreadsheet Cobra attached a few posts above yours but nothing attached to yours just the link to your build thread, the link to the onshape model and the 3 screenshots...

Well let’s give it another shot then. Weird.

CG location change_332it.xlsx

edit: I think I managed to fix the original post too. Hopefully.

[STAATS]

Onshape is super cool, I’m extremely impressed. You can get to your CAD from any computer, export DXFs straight from sketches, there’s even an iPhone app that works surprisingly well. I’ve switched all my personal stuff over.

As for the excel sheet, it should just be an attachment to my post above. I see it on my end, so I hope it’s showing up for everyone.

Hmm I am definitely missing something then... I can see the spreadsheet Cobra attached a few posts above yours but nothing attached to yours just the link to your build thread, the link to the onshape model and the 3 screenshots...

[Bry5on]

Awesome!
Although I can't find a link to the excel sheet?
Also thanks for the link on onshape that's a pretty cool service being that its free for hobbyists, may be a better location for me to house the random E46 M3 related CAD models I have collected over time than on Google Drive for sharing

Onshape is super cool, I’m extremely impressed. You can get to your CAD from any computer, export DXFs straight from sketches, there’s even an iPhone app that works surprisingly well. I’ve switched all my personal stuff over.

As for the excel sheet, it should just be an attachment to my post above. I see it on my end, so I hope it’s showing up for everyone.

[STAATS]

I've been detailing a bunch of suspension geometry modeling work in my build thread here - it's ready enough to share with folks here if you're interested in really getting your suspension right. If you're lowering the car, especially if you're lowering the front, it's easy to mess the balance up.

Simplified CAD model of the e46 M3 suspension: https://cad.onshape.com/documents/a1...66f543dbff2801

CG and roll modeling in attached excel (CG location change_332it.xlsx):


As well as modeling suspension curves for different height settings:

Awesome!
Although I can't find a link to the excel sheet?
Also thanks for the link on onshape that's a pretty cool service being that its free for hobbyists, may be a better location for me to house the random E46 M3 related CAD models I have collected over time than on Google Drive for sharing

[Obioban]

I've been detailing a bunch of suspension geometry modeling work in my build thread here - it's ready enough to share with folks here if you're interested in really getting your suspension right. If you're lowering the car, especially if you're lowering the front, it's easy to mess the balance up.

Simplified CAD model of the e46 M3 suspension: https://cad.onshape.com/documents/a1...66f543dbff2801

CG and roll modeling in attached excel (CG location change_332it.xlsx):


As well as modeling suspension curves for different height settings:

Awesome!

[Bry5on]

I've been detailing a bunch of suspension geometry modeling work in my build thread here - it's ready enough to share with folks here if you're interested in really getting your suspension right. If you're lowering the car, especially if you're lowering the front, it's easy to mess the balance up.

Simplified CAD model of the e46 M3 suspension: https://cad.onshape.com/documents/a1...66f543dbff2801

CG and roll modeling in attached excel ( CG location change_332it.xlsx ):


As well as modeling suspension curves for different height settings:

[Driver407]

duracellttu
Been reading and learning about flat ride all weekend. Just finished all 25 pages here among others.
You seem to have gone down a very similar path and asked the same questions I have had going through all of it.

Bought a set of TCK D/A with 400/500 as recommended by Mr. Kline. Is a dedicated track car that sees some backup-daily usage. 3350lb no driver. 50% corner balanced. Looking into flat ride info and had a few questions about your journey.

I see you went down the path of TCK S/A with ~350 and ~700. Said it was pretty bumpy? Did some adjustments and didn't really hear if it helped? Think you even debated getting D/A rears it seems.
You also inquired about why TCK recommended the 400/500 to you (My setup). Without much further forum discussion. Just trying to see what angle he has vs the flat ride mentality. If you ever maybe discussed that elsewhere.

Curious where you landed after all this time. Did you get the original 350/700 setup to work?
Did you end up happy with the outcome after doing flat ride on the tck?

Just looking for some tips. Literally just did my corner balance and yearly alignment last month. Kinda wish I had learned all this before that! lol. My car has felt great the last few track days but now this has me intrigued.

[Drewrivera]

Anyone know if alpina set ups work for M.? Was it just springs or did it have a whole set of different dampers? 😶😶

[cobra]

Can someone see if the attached excel works for them, and check my math?

I tried it on my car and it got me within 1/4" of the numbers I measured. Maybe there is something wrong with the motion ratio stuff but it at least gives you an idea...


It lets you input spring parameters, vehicle weight, and shock travel, and lets you know how close you are to coil bind at bottom-out. I also included every spring Eibach makes which is going to be reasonably close to other manufacturers of 2.25/60/2.5 springs.