Spring Rate Explanation

[danewilson77]

Typically listed in lbs.......what does it mean?

What does about "about 400 lbs front and 650 lbs rear" vice "about 400 lbs front and 470 lbs rear" mean.

I think I know.....but just wanna make sure I know.

Thanks

[zhpnsnv]

I believe that's lb/sq inch, but I could be wrong on that. Basically, it's how stiff the springs are. Springs serve to allow the shock to do its job - if they're not matched well (or perfectly), you get an oddly handling/riding suspension.

As far as front to rear spring rate theory and practice, that's way beyond me. Suffice to say that for the dynamics/characteristics of our cars, we have stiffer springs in the rear. 400 lbs would probably be a decent street setup for an E46. 650 would be pretty stiff, I'd imagine. I have 6-somethings on my MINI, and it's wayyyyyyy too stiff for the street.

One thing I learned is that when/if you buy coilovers and have them installed (or install them), test and check the spring rate. I bought from a VERY reputable suspension company (KW V2) only to find that the springs they sent me were progressive (not good for track) instead of linear and NOT the correct rates. Had I not tested them, I'd have found out mid-corner at the limit when the rate changes. Oooops!

All of these variables/uncertainties/areas of expertise are why I tend to trust the people who do real track setups even if a person isn't looking for a track setup: TC Kline, Turner, etc...

[danewilson77]

OK......so....about 400 lbs front and 470 lbs rear.....would be a decent setup then.

Do we have stock spring rate data for zhp springs?

[Crickett]

Do we have stock spring rate data for zhp springs?

I believe that's a much more complicated can of worms than you'd expect; I do not believe that there is one spring rate for all ZHPs. From what I can remember (I'll redo the research in a bit), the spring rate for your car takes into account all of the options it was ordered with; things like the H/K sound system, navi, auto vs 6MT, etc. all change the weight distribution & therefore what springs you got.

Somebody on E46F had compiled a lot of data from users on what springs they have on what models; I'll see if I can't dig that up.

[zhpnsnv]

I have no way to tell if that's a decent setup or not. I'd be more concerned with whether or not the springs were linear or progressive, first. Linear springs keep their rate throughout their travel; progressive are different depending on the load. Personally, I don't like that feel.

And I don't know the stock spring rates; 400 and 470 sounds pretty mild to me.

[Crickett]

Ok, after digging a bit through E46F, I found one of my original responses to someone asking nearly the same question:

Here's the thread I was thinking about***********: http://forum.e46fanatics.com/showthread.php?t=397880

Secondly, here's a good post that sums it up:

The parts that come with this package are exactly the parts that the ZHP differs from the sports package. The springs are not there, because the springs that the factory puts on the cars depend on how much the car weighs after all the options the car is equipped with, and not on what package the car comes with (talking about ZHP vs. ZSP here).

Also, from the pictures folks had posted of their springs, the E46 has linear front springs & progressive rear springs. The rate of the springs are indicated by color-coded stripes; I believe most ZHPs (& ZSPs) have three green stripes on the rear springs.

And here's a response about spring rates specifically:

It's a bit difficult to specify "a rate" for a progressive rate spring. I can link you to the following site though where the force required for up to the first 4-5 inches or so of spring compression has been measured.

http://spreadsheets.google.com/pub?key=pjaUgOkna3I3mP8cOvc5vZQ

As you can see, the front springs are close to being a linear 140 lb/in rate. Rears are progressive and vary from roughly 375-750 lb/in. The ZHP spring measurements were made using the springs from my car.

This should give you an approximate answer to your question but... why do you ask?

And finally, here's the latest (as of Nov 06) spreadsheet of color codes & options complied by E46F's JPR: Spring Data 253.pdf (http://tcholo.net:8080/docs/SpringData253.pdf)

[johnrando]

Thanks for all that info. Unfortunately, it says I can't access the Spring Rate Data PDF.

[danewilson77]

I have no way to tell if that's a decent setup or not. I'd be more concerned with whether or not the springs were linear or progressive, first. Linear springs keep their rate throughout their travel; progressive are different depending on the load. Personally, I don't like that feel.

And I don't know the stock spring rates; 400 and 470 sounds pretty mild to me.

I would think Turner set them up well though.

Droid + Tapatalk = FTW!

[Crickett]

Thanks for all that info. Unfortunately, it says I can't access the Spring Rate Data PDF.

Bah . . . m'bad. Should be fixed.

[johnrando]

Bah . . . m'bad. Should be fixed.

Thanks! I can view it now. Bummer it doesn't have mine.