FCM E46 M3 Ride Harmonizer suspension spreadsheet - aka Flatride !!!

[e46m3_06]

I don't seem to be running out of bump travel per the tie wraps but it's close.
I worked backwards through the spreadsheet and it looks like when i set the weight distr. to 50/50 and enter the same spring rates front and rear I get a wheel rate to spring rate ratio of .88 front and .49 rear. From what I've read the rear's are a bit high but the front is really low. Some sites say .98 F and .44 R. I used 3415 pound car. i coulda made a mistake but the rates are close enough that I'm assuming I didn't.

[maupineda]

the factor is .88 F and .45 R. this is derived from a motion ratio of .94F and 0.67R

[e46m3_06]

Ahh darn I realize now he actually put his measured motion ratio in the spreadsheet at the bottom. He's using .938F and .7R. I suppose the only difference could the angle of the struts/shocks but that's not a large factor considering a degree or two.It's hard to see how people get such different measurements though.

[Gearhead55]

Hey guys. I was active on the M3forum.net before it died under the same username, just signed up here.

I have been running a flat ride set up with MCS 1wnr dampers on the street for a while now and just did my first track day with the set up last Sunday. I had been very happy with the set up on the street and in the canyons. Even with track-car-stiff springs rates the ride was reasonable on the streets. Now I am again impressed after tracking it. The car had tons of grip, minimal body roll, and it managed track surface imperfections and undulations much better than my previous Bilstein PSS set up. The predictability gave me much more confidence and allowed me to put down very consistent times and beat my PB even though it had been more than a year since my last track day. The only "downside" to the set up is the front end dive under braking, which I honestly don't mind that much because it allows for deliberate weight transfer. If it was a dedicated track car I might consider a stiffer front spring.

As it sits I am running 448/840 swift springs with a 30mm whiteline front bar on the middle setting, stock rear bar. I think that puts me at 1.05 R/F and 77.8% FRC. I will be switching to the softer front bar setting before my next track day, as I wouldn't mind it being biased more towards oversteer. If that isn't enough I may convert the rear to a true-coilover and pick a rate for a higher R/F.

[Chas3n]

Question, whom here has messed with the spring rates on the Eibach coil overs? Were there any limitations?

Thanks

[Obioban]

Question, whom here has messed with the spring rates on the Eibach coil overs? Were there any limitations?

Thanks

I had them on the wagon, but didn’t bother— the shocks just felt like junk. Replaced them with Koni yellows and was much happier.

[r4dr]

I had them on the wagon, but didn’t bother— the shocks just felt like junk. Replaced them with Koni yellows and was much happier.

Did you pair them with Eibach Pro-Kit springs? Or Dinan?

I've got an E91 wagon on Pro-Kit springs & B4 sport shocks, wish I had gone with Koni yellows in hindsight.

[Obioban]

Did you pair them with Eibach Pro-Kit springs? Or Dinan?

I've got an E91 wagon on Pro-Kit springs & B4 sport shocks, wish I had gone with Koni yellows in hindsight.

I have Dinan springs with the konis on the wagon.

Our former e91 had konis with eibach springs and it was... eh, fine. I think the non M e9Xs just aren’t a great handling platform, and not because of springs or shocks.

[r4dr]

I have Dinan springs with the konis on the wagon.

Our former e91 had konis with eibach springs and it was... eh, fine. I think the non M e9Xs just aren’t a great handling platform, and not because of springs or shocks.

Was it AWD? Manual?

[Obioban]

Was it AWD? Manual?

Rwd manual.

[r4dr]

Rwd manual.

That's exactly what I've got. Love it as a DD, but it's about due for an upgrade to the M control arms + bushings.

[Obioban]

That's exactly what I've got. Love it as a DD, but it's about due for an upgrade to the M control arms + bushings.

Yeah, I did the m3 subframe bushings and it helped some.

[Chas3n]

I had them on the wagon, but didn’t bother— the shocks just felt like junk. Replaced them with Koni yellows and was much happier.

That’s not good news to hear.. What didn’t you like about them?

I believe the the ZCP‘s I’m looking at a 350 f and a 650ish R. My question if the rear damper will comply well with that much of an increase in sprig rate.

[D-O]

After getting jerked around by Eibach I am planning to move to TCK SA. After fooling with the spreadsheet for a while I am beginning to get a feel for it, and have come up with some options. This is strictly a street car.

Here are three options that include the stiff Turner sways front and rear:



How much different are these going to feel? I see the difference in bounce freq. and bar and spring ratios, but how do these translate to driving feel?

Here is an option with a Hotchkis bar on the front (set to med) and the stock bar in the rear.



Flat ride in the neutral zone of FRC, but much less roll stiffness, with the springs doing more of the work and the sways doing less. How will this feel compared to the above options?

Anyone have the wall thickness and bar and arm lengths for the Hotchkis rear bar? I would like to plug it in and see how it compares to the Turner.

The GC bars look very interesting, but the purchase options on the their website don't really coincide with the spreadsheet.

TIA.

Jesse

[Obioban]

Neutral FRC is ~75. Those a look a bit oversteer biased to me.

I ended up in the middle of you’re range— ~362 up front, ~675 in the rear.