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

[elbert]

IIRC I'm also 6", but I went with Eibach's "extreme travel" line of springs to have sufficient travel. They're basically barrel springs, so you can more compression without binding.
https://eibach.com/us/i-83-eibach-xt...me-travel.html
^ not my actual spring, just a link to a product in the line

Hmm, seems to be available only in 2.5" diameter. Bah.

[maupineda]

Perches and adapters are easy and cheap to source.

[Obioban]

Hmm, seems to be available only in 2.5" diameter. Bah.

They work fine on 65mm perches, as well. I switched over to Ohlins perches for just that reason.

[The M]

Thanks for all the responses guys. It's great to not have to reinvent the wheel so I can hopefully order the right length this time.

[cobra]

IIRC I'm also 6", but I went with Eibach's "extreme travel" line of springs to have sufficient travel. They're basically barrel springs, so you can more compression without binding.
https://eibach.com/us/i-83-eibach-xt...me-travel.html
^ not my actual spring, just a link to a product in the line

At full compression, if I didn't have a bump stop (metal on metal), I'd be 2mm more compressed than the springs allow for. But, I do run a bump stop, and it should never get compressed to less than 2mm, so I should be in range at all times. There has been zero evidence of any coil bind, so reality seems to back up the theory.

All that said, I'm going through that because I want the spring above the tire, because I like to run ET35 tires on track. If you're an ET25 person, just run a longer spring. :P

Hmm... even with the XT springs, a 6" 350lb version only has 4.1" of travel. How much bump travel do you have and what rate are you running?

Also, random question.... anyone know what the maximum wheel width and offset is allowed to fit a 2.25" spring next to the tire/wheel?

[The M]

In the rear...
Your spring length will depend what adapters and ride height adjusters you are using since they are different thicknesses. The stock spring pads are 5mm (0.20") each.

Stock springs are 8.75" long and compress just under 3 inches statically, at which point it moves into the 550lb/in region (progressive rate). So the total height of the stock spring + pads is: 8.75 + 0.20" + 0.20" = 9.15".

If you are running 550lb straight rate springs in back, they will compress just under 2.0 inches statically, so a 1.0 inch difference. At the wheel that translates to about a 1.4 inch difference. So if you wanted to maintain stock ride height, you would want a spring + adjuster height of 9.15" - 1.0" = 8.15". So you'll need to measure your spring adjuster minimum height and see what it is. I'm guessing it's probably .75" ish, meaning the longest spring you can run is a 8.15 - .75 = 7.4" or a 7" spring. If you want to lower it, then the 6" that you have sounds right. How low is it and what is your height adjuster set to?


In the front...
Are those 60mm ID Swift springs? They only have 4.1 inches of usable stroke and 4.5" max stroke. At 336lb/in, you are already using 2.5" just to hold up the car, meaning you only have 1.6" of travel before it starts to bind. Depending on your shock setup (bump travel avail) you might need to consider stiffer springs, longer springs (8 or 9 inch), and/or barrel springs.


At least, I think those numbers are right. I am going through this right now.

My rear has Ground Control weight jacks extended nearly all the way up but with the 6" springs it's still too low for me. Height was perfect with my previous track only setup of 900lb 6" springs but the 550 street springs just compress too much.

And yes, the fronts are 60mm Swifts. I guess I wasn't thinking clearly enough about how much the softer springs would compress, leaving barely enough spring remaining for dynamic travel.

The car height looks nice with the short springs but I'll get new ones to raise it to be more usable.

imageimage

[cobra]

Yeah, 7" springs should do the trick.

[Cronenberged]

1) ~45 lbs
2) 59 lbs
3) ~50 lbs
4) ~45-50 lbs... mostly wire

Do you have the DIY on 3?

[Obioban]

Hmm... even with the XT springs, a 6" 350lb version only has 4.1" of travel. How much bump travel do you have and what rate are you running?

Also, random question.... anyone know what the maximum wheel width and offset is allowed to fit a 2.25" spring next to the tire/wheel?

Just saw this. My shocks don't have a ton of travel-- 110mm total IIRC, but there's a bump stop in there so functional travel is even less. have it set at 60% bump travel, of which some of that is the bump stop-- so 66mm of "travel", but really more like 40-45.

I have a 375lb on the driver side and 350lb on the passenger side IIRC.

I am absolutely right at the design limit of the spring-- but there's zero evidence that coil bind has ever occurred.

[Obioban]

Do you have the DIY on 3?

For others reading:

3) lithium ion battery/battery cable delete

4 cylinder e46 coupes (not sold in the USA) had the battery installed in the drug bin. My lithium battery is 5.6 lbs, so it wasn't doing anything meaningful for weight distribution in the trunk. I bought the factory under hood wiring parts for a 4 cylinder car and made a bracket to mount it in the drug bin. I pulled all the factory battery mounting hardware out of the trunk and, since my interior was already gutted at the time, pulled the positive battery cable that runs to the trunk (which was surprisingly heavy-- 8 lbs per real OEM IIRC).

I even happen to have an up to date picture on hand, as I took a picture of the washer fluid level a month ago to see if I'm losing fluid (just replaced the pump gasket because I was).

[Chas3n]

Anyone with the Eibach pro kit springs play around with their sway bar sizing?

I have the Hotchkis on there now, but want to shoot for an optimized freq.

[lvm3sm46]

I recently had my corner weights taken and started messing with the spreadsheet. What section of the spreadsheet should I start with?
Regarding the spring rates, aren't we limited to what is actually available for sale? Like 700# 750# etc.

I am trying to get 1.9 hz front, 2.1hz rear like Obioban mentioned.

attached is my corner weights and what I have input at the moment.

[Cronenberged]

Should be able to order the weights you want
from GC thats where I'm ordering mine from.

[cobra]

I recently had my corner weights taken and started messing with the spreadsheet. What section of the spreadsheet should I start with?
Regarding the spring rates, aren't we limited to what is actually available for sale? Like 700# 750# etc.

I am trying to get 1.9 hz front, 2.1hz rear like Obioban mentioned.

attached is my corner weights and what I have input at the moment.

Just get close with the rate, I highly doubt anyone can tell the difference between a few % difference or imbalance. Besides - springs don't always measure what they're labeled at. I bought an Eibach 600lb spring that measured 580 on a calibrated tester.

[Obioban]

Yeah, you're limited to what exists. You can game it by using metric spring rates, and springs are cheap enough that you can buy a couple and measure them to get one close to what you're looking for. E.g. but a couple 700s and use the one that measures high.