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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.


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Old Thu, Oct-11-2018, 06:43:22 PM   #71
pawa_k2001
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Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

Trying to get my head around this while I am in the middle of rebuilding my suspension.

Just had my AST 4100s rebuilt which I wanted to run with my previous setup of 550f 6" spring/650r 5" spring. I also have a Hotchkis 30mm front sway bar.

If I am to understand this correctly, it would be beneficial for me to go to a 350lbs front spring? If it helps any, M3 will be around 13.5f/13r ride height from where it will be corner balanced(will be raising corners since I don't want to go below the 13.5/13 setup)
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Suspension: AST 4100 GTS Suspension, Vorshlag camber plates, Mason front strut bar
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Old Thu, Oct-11-2018, 07:22:30 PM   #72
gearhead55
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Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

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Originally Posted by pawa_k2001 View Post
Trying to get my head around this while I am in the middle of rebuilding my suspension.

Just had my AST 4100s rebuilt which I wanted to run with my previous setup of 550f 6" spring/650r 5" spring. I also have a Hotchkis 30mm front sway bar.

If I am to understand this correctly, it would be beneficial for me to go to a 350lbs front spring? If it helps any, M3 will be around 13.5f/13r ride height from where it will be corner balanced(will be raising corners since I don't want to go below the 13.5/13 setup)
What do you use the car for?
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Old Thu, Oct-11-2018, 07:31:24 PM   #73
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Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

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Originally Posted by gearhead55 View Post
What do you use the car for?
I do a weekend at the track every other year. M3 is used for Tail of the Dragon and roads like that mostly these days(I host multi-day drives once in a while). Basically, imperfect roads and slower speed corners.

My old E30 that is now sold.
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Suspension: AST 4100 GTS Suspension, Vorshlag camber plates, Mason front strut bar
Engine: Evolve R Software, Status Gruppe SCZA exhaust
Exterior: Status Gruppe front valance
Brakes: Bimmerworld brake stiffener kit
Wheels: Apex ARC-8 18x9.5" W/ Dunlop Star Spec tires 275/35/18
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Old Thu, Oct-11-2018, 07:52:50 PM   #74
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Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

Quote:
Originally Posted by pawa_k2001 View Post
I do a weekend at the track every other year. M3 is used for Tail of the Dragon and roads like that mostly these days(I host multi-day drives once in a while). Basically, imperfect roads and slower speed corners.

My old E30 that is now sold.
Morning run at Hwy 151, Heavens Ascent in a E30 BMW 325i S52 Swapped - YouTube
Gotcha. And how do you feel about the ride quality and stiffness as it is now?
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Old Thu, Oct-11-2018, 08:01:18 PM   #75
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Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

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Originally Posted by gearhead55 View Post
Gotcha. And how do you feel about the ride quality and stiffness as it is now?
Its on the firmer side but livable(wouldn't want any firmer). I had to go to softest front sway bar setting since it was pushing in the slow corners.
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Suspension: AST 4100 GTS Suspension, Vorshlag camber plates, Mason front strut bar
Engine: Evolve R Software, Status Gruppe SCZA exhaust
Exterior: Status Gruppe front valance
Brakes: Bimmerworld brake stiffener kit
Wheels: Apex ARC-8 18x9.5" W/ Dunlop Star Spec tires 275/35/18
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Old Thu, Oct-11-2018, 08:21:06 PM   #76
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Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

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Originally Posted by pawa_k2001 View Post
Its on the firmer side but livable(wouldn't want any firmer). I had to go to softest front sway bar setting since it was pushing in the slow corners.
So yea, dropping the front rate some would probably be a good way to go. 350 front 650 rear would give you a 2% flat ride, which is similar to what my set up will be. You could also up the rear rate slightly and drop the front rate.

Iíll let Shaikh chime in with the expert opinion though.
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Old Fri, Oct-12-2018, 07:36:11 PM   #77
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Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

I'm very happy to see you guys using / testing these ideas with the spreadsheet as a tool.

Quote:
Originally Posted by pawa_k2001 View Post
Trying to get my head around this while I am in the middle of rebuilding my suspension.

Just had my AST 4100s rebuilt which I wanted to run with my previous setup of 550f 6" spring/650r 5" spring. I also have a Hotchkis 30mm front sway bar.

If I am to understand this correctly, it would be beneficial for me to go to a 350lbs front spring? If it helps any, M3 will be around 13.5f/13r ride height from where it will be corner balanced(will be raising corners since I don't want to go below the 13.5/13 setup)
Right now, assuming about 51% front weight distribution on your E46 M3, if you followed gearhead's great recommendations to use 350/650, you'd be around 1.90 Hz front, 1.99 Hz rear or 5% Flat Ride. That would be very reasonable. The current 550/650 gives 2.38 Hz front and 1.99 Hz rear which is very pitch-biased and wouldn't make for stable / confidence-inspiring driving especially on uneven or damp roads as you're likely to encounter on the Dragon.

There's also a calculation you can make for the ideal Flat Ride bias based on your nominal road speed. If you're driving windy backroads (say 40-50mph avg speed) then you may want a little more rear frequency bias vs. if you're primarily driving a track (say 80mph average speed). The faster you go, the lower your rear frequency bias needs to be as the vehicle covers the distance between front and rear wheels (the wheelbase) more rapidly. I actually plan to add that 'ideal Flat Ride bias' calculation based on road speed to an upcoming rev.

For backroad use I generally like to keep the rear frequency under 2.0 Hz. You have much better compliance. The 350/650 would be good to test. Those rates would lower your FRC slightly (from ~81.0 with 550/650 to ~79.4% with 350/650) which reduces understeer, plus give you 5% Flat Ride instead of pitch. At lower road speeds your rear suspension would be able to catch up to the front more quickly and the car would settle faster and be ready for the next turn / transition. A key to making this all work is having enough front negative camber plus front caster (which becomes dynamic camber gain) available to plant the outside front tire and keep it flat in cornering.

Generally, if you're getting understeer you may want to soften the front dampers on rebound and bump. It's also possible you're getting bump stop engagement (if there's one present, assuming there is). Also - and importantly - keep in mind that the presence of excessive front gas force (which is quite possible assuming it's an AST with at least 19mm front shaft diameter) would induce a higher perceived oscillation frequency and cause more understeer on the front end as it could be fighting for grip as the tire bounces across the road at ~5Hz or higher frequency just from the damper's gas spring. If there's an external reservoir, I would like to see the fill pressure at 100psi or lower and use as soft a bump setting as possible. Dyno testing is the ideal way to know how low you can go with gas fill pressure but I did this on a set of Motons (related designed to AST although not necessarily the same as what you have) a couple years ago and there was no cavitation although slightly higher hysteresis. The front strut gas force dropped from 115 lb (!!!) to 57 lb. That's still quite high, but anything around 40-50 lb would be more tolerable.


Can you get tire temps at an autocross / track day or some other safe environment? Usually it's bump stops first, then damper settings, then insufficient front negative camber. Also watch for too much rear toe-in, and you'd want some front toe-out to aid in initiating front tires slip angle / turn-in response.

Also, you can use a 58mm or 76mm rear bump stop from 5Xracing (or anywhere that sells Speedthane bump stops) and do further tuning with bump stops spacers / packers to increase rotating. Our 47mm 'strut' style bump stop will fit over a 19mm shaft (and more tightly on a 22mm shaft) and may be softer density than what AST provides. In this way, you can use the bump stops to encourage *slightly more* rear bump stop contact to help keep the car neutral when in hard cornering instead of having the front bump stop dominate the cornering behavior.


Just some ideas to help you fine-tune for as close to perfect, neutral handling for your driving style and conditions.
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'02 Fat Cat Motorsports E46 330i / 3.46 Wavetrac / FCM Elite Bilstein suspension / lightened / NASA TTC prep / Team Rival S

Best laps: 1:48 Laguna Seca / 2:11 Thunderhill w/bypass / 2:16 Buttonwillow 1CW

Last edited by ShaikhA; Fri, Oct-12-2018 at 07:43:22 PM.
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Old Fri, Oct-12-2018, 08:24:48 PM   #78
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Default FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffness)

Wow, thank you ShaikhA. I understand somethings, try to understand other but a few are over my head. Lol

I run 2.8-2.9 degrees negative camber, 0 toe and max caster(that Vorshlag plates give me) in the front. Rear I run 1.8-2.0 negative camber with around factory toe in.

I did get a synopsis sheet from the AST suspension rebuild, canít say I understand it much.

At Petit LeMans right now but I was able to find a few pictures on my phone that may help.

Every time I rebuild my suspension I try take it to the next level that is within my understanding(or lack of). This time I want to do the following

- Custom alignment
- Corner balance
- Set sway bars to neutral
- Play with suspension compression settings
- Possibly change a few things to test this new to me FCP/pitch/flat ride.

IMG_0954.JPGIMG_9058.JPG


Sent from my iPhone using Tapatalk
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Suspension: AST 4100 GTS Suspension, Vorshlag camber plates, Mason front strut bar
Engine: Evolve R Software, Status Gruppe SCZA exhaust
Exterior: Status Gruppe front valance
Brakes: Bimmerworld brake stiffener kit
Wheels: Apex ARC-8 18x9.5" W/ Dunlop Star Spec tires 275/35/18
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Old Fri, Oct-12-2018, 08:50:54 PM   #79
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Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

Czesc, Pawel! Na pewno. The alignment settings seem reasonable though you would enjoy some slight front toe-out (say -0.150 deg total which is less than 1/16 inch on 18" wheels).

The AST damper dynos do show a pretty strong and typical linear-piston bias toward rebound as the shock speeds get higher. That would suggest jacking down as the road gets rougher. I'd run the dampers as soft as possible. You'd have a much better setup if you could get a double-digressive piston (DDP) which I think they finally started making some years ago. Bilstein has used them for decades!

The dyno sheet also indicates 150psi, which calculates to 66 lb gas force on a 19mm shaft, or 88 lb gas force on a 22mm shaft. Even at 66 lb, that's going to be very noticeable on rougher / rippled surfaces as an additional 'bouncing' of the tires over the surface. I can't say how little nitrogen pressure the ASTs need to still operate properly so that's up to them to advise you. You may be at the minimum allowable nitrogen pressure already.

For now, with the 350/650 springs and the other changes (including bump stop investigations) including corner balancing and alignment you should have a more neutral and fun M3!
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'02 Fat Cat Motorsports E46 330i / 3.46 Wavetrac / FCM Elite Bilstein suspension / lightened / NASA TTC prep / Team Rival S

Best laps: 1:48 Laguna Seca / 2:11 Thunderhill w/bypass / 2:16 Buttonwillow 1CW
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Old Fri, Oct-12-2018, 09:47:06 PM   #80
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Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

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Originally Posted by gearhead55 View Post
So to update you guys, I spoke with Shaikh a couple weeks ago about my build and Iíve started compiling parts.

Some background info:
The previous owner of my car installed PSS9s, which have been on there for at least 40k miles now. They perform quite well as a dual purpose suspension but as the car becomes more of a track car for me (and as my skill has improved) Iíve started to feel that itís time to switch to a stiffer linear spring. I originally planned on having Bilstein revalve them for me, but then I found the various threads in which Shaikh discusses his process and decided to go that route. He helped me choose spring rates and sway bars and talked me though his revalving philosophy. Iím sold and excited to get it completed and installed.

Ultimately I decided on Swift springs because they have a reputation for high quality and consistent spring rates. I went with a 6in 8kg (448lbs) front and 5in 15kg (840lbs) rear. Using the spreadsheet this should give me a slight flat-ride (3% if I remember correctly). I plan on using the eibach 27mm front bar in the softest setting initially and then stiffen if needed.

I ordered the springs yesterday and they came today! I went with 6in front with a helper spring and 5in rear with a RE weight jacker because I was worried about not being able to go low enough in the rear with a 6in spring. I wanted to make sure the weight jacker would fully articulate. My car is quite low, as 12.5in hub center to fender height in the rear.

I love the color of the springs too:



I should have the coilovers off by the end of the month. Hopefully Iíll have everything back and re-assembled by early December.


Sent from my iPhone using Tapatalk
Thanks for this update, Jim! I really like the quality of the Swifts (or Hyperco). They definitely allow for more spring travel which is important. I've got a growing number of builds to do and need to keep valving although I love watching this thread and contributing as more people join in. I appreciate you working with Pawa The 'recipe' gets clearer once we have a basic appreciation for Flat Ride, then FRC - everything else that needs adjusting goes around that.

I wanted to mention again, since we're using PSS9s for your build, that I haven't been able to find a way to use the adjuster as a functional low-speed damping tuning aid so I turn it to 'closed' then valve (and add Ripple Reducer holes) from there. With the shaft bypass port closed, we can maximize the Ripple Reducer feature, which I feel is more valuable than trying to utilize the unusual design of the PSS9 shaft. The PSS10 is an improved design, although I would still set that closed and valve as needed.
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Best laps: 1:48 Laguna Seca / 2:11 Thunderhill w/bypass / 2:16 Buttonwillow 1CW
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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)