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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 Wed, Oct-02-2019, 10:31:48 PM   #781
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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 TheGenius46M View Post
Good then my theory has to be correct! Lol.

Front: 425lb 2.25ID 7” Hyperco

Rear: 850lb 2.25ID 5” Hyperco

I have weight jacks in the rear but feel getting that preloaded as well wouldn’t hurt. Right now the front is the primary issue though.




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hi mate. can you measure the amount of bump travel available when the car is at static height?
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Old Thu, Oct-03-2019, 12:31:37 AM   #782
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Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

Quote:
Originally Posted by TheGenius46M View Post
Good then my theory has to be correct! Lol.

Front: 425lb 2.25ID 7” Hyperco

Rear: 850lb 2.25ID 5” Hyperco

I have weight jacks in the rear but feel getting that preloaded as well wouldn’t hurt. Right now the front is the primary issue though.




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I hope my 6” 425 springs will work…


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Old Thu, Oct-03-2019, 07:33:38 AM   #783
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Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

I'd say the 6" 425 is a good direction, I'm using 6" 430 and 400 on LF and RF (to get symmetric left and right front ride frequencies for the different LF and RF corner weights).

I'm also using a Bilstein ~100 lb/in 2" (IIRC) helper spring up front (no helper in the rear, not needed). I find a front helper an important addition to keep the spring in full contact at full droop unless your damper is droop limited. A front bar being present will also limit droop but I don't like to rely on that.
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Old Thu, Oct-03-2019, 12:28:24 PM   #784
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Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

Quote:
Originally Posted by TheGenius46M View Post
Good then my theory has to be correct! Lol.

Front: 425lb 2.25ID 7” Hyperco

Rear: 850lb 2.25ID 5” Hyperco

I have weight jacks in the rear but feel getting that preloaded as well wouldn’t hurt. Right now the front is the primary issue though.




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I can't find any stroke specs listed for those springs, anywhere
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Old Thu, Oct-03-2019, 03:41:08 PM   #785
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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 Obioban View Post
I can't find any stroke specs listed for those springs, anywhere
I've always found that annoying about Hyperco, as opposed to Eibach who lists all that info in their catalog.
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Old Thu, Oct-03-2019, 03:58:03 PM   #786
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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 Zzyzx85 View Post
I've always found that annoying about Hyperco, as opposed to Eibach who lists all that info in their catalog.
Yeah-- as does Swift, as does Vogtland, etc...
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Old Thu, Oct-03-2019, 04:12:39 PM   #787
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Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

FWIW Helper springs are very low spring rates (like just enough to keep the spring against the perch) and usually made from flat stock. They should be fully compressed under the weight of the car and are only there to keep the spring on the seat when the suspension is at fool droop: jacking or jumps. Tender springs are just shorter main springs and are used in conjunction with stiff main springs and should not be fully compressed under just the weight of the car. A softer tender with a stiffer main spring essentially gives you a progressive spring rate without a progressive spring.

Also your front end vagueness on the highway is likely more alignment then the spring coming unloaded. assuming your car weights 3200lbs and there is about the same amount of weight on each corner. with your 425lb/in front spring your front end would need to come up almost 2 inches before your springs would even unload. Usually front end vagueness is caused by not enough front toe, either toe-in or toe-out. Toe-in gives better front end stability at speed and during braking. Toe-out makes the car more willing to change direction quickly at the expense of stability and too much can make the car feel darty. Zero toe is bad and makes for vague steering.
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Old Thu, Oct-03-2019, 08:12:44 PM   #788
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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 Obioban View Post
I can't find any stroke specs listed for those springs, anywhere


Here’s the info I acquired from a Hyperco engineer over the phone back in February before I switched spring rates. This is just what I was able to jot down over the phone so excuse the informality.




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Old Thu, Oct-03-2019, 08:33:12 PM   #789
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Default Re: FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffn

Quote:
Originally Posted by Cristov9000 View Post
FWIW Helper springs are very low spring rates (like just enough to keep the spring against the perch) and usually made from flat stock. They should be fully compressed under the weight of the car and are only there to keep the spring on the seat when the suspension is at fool droop: jacking or jumps. Tender springs are just shorter main springs and are used in conjunction with stiff main springs and should not be fully compressed under just the weight of the car. A softer tender with a stiffer main spring essentially gives you a progressive spring rate without a progressive spring.

Also your front end vagueness on the highway is likely more alignment then the spring coming unloaded. assuming your car weights 3200lbs and there is about the same amount of weight on each corner. with your 425lb/in front spring your front end would need to come up almost 2 inches before your springs would even unload. Usually front end vagueness is caused by not enough front toe, either toe-in or toe-out. Toe-in gives better front end stability at speed and during braking. Toe-out makes the car more willing to change direction quickly at the expense of stability and too much can make the car feel darty. Zero toe is bad and makes for vague steering.


So since I switched to 7” springs and replace my steering lower u-joint (the long rod not just the guibo) I noticed a big improvement in the vagueness.

I am running zero toe which I’m fully aware doesn’t help, but I’ve been running zero front toe on this car up front for 6 years now but never once had an issue until the mcs. I’m on Dunlop z3s which also doesn’t help. My federal 595 rsrrs on my track wheels have much less vagueness.

I think the issue became more obvious as suspension components wore out. I replaced the remaining half of the front end this past year because I couldn’t take it anymore and that slowly made the issue better but I always was under the impression the 6” spring by itself may have been unloading, especially given I was running only 3 clicks of compression from soft. Front sway has always been set to full stiff because I prefer it.

Now if I go with a 6” 425 and do a tender, how do I figure out the appropriate tender rate and length for MY application (not just what’s accepted norm) so that I can pretty much just use the tender for smaller stuff but the main spring will take over for when I want the feedback of my 425? I feel I would realistically want like a 100lb tender spring to accomplish this but don’t believe they exist?

There is only 0.5” of play at best that I could visually see (will have to measure this) at full droop so a friend of mine and I were talking last night and feel that for what I want to accomplish maybe it makes sense to have a custom spacer made to fit between the spring and spring perch that is just enough to preload the spring at full droop, but also allows me to not have to worry about any disadvantages of a dual spring rate setup?

I would want as low as possible of a tender spring rate to prevent the cross over from tender to main spring being abrupt. I was read that a lot of racers do this for that very reason.

Thoughts?


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Old Thu, Oct-03-2019, 09:19:15 PM   #790
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Default FCM E46 M3 Ride Harmonizer suspension spreadsheet (bounce freqs, FRC, roll stiffness)

Wrong thread
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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)