Spring interchangeability

[JGood]

The e90 drop hat thread got me thinking... if the spring hats are the same, that means the springs are the same diameter. I'm curious how the spring rates/lengths compare? What other models have the same dimensions springs? With all the aftermarket springs available for the various models, this could really open up some options as far as ride height and spring rates go. For instance, maybe H&R Race springs for another model would have an e30 at the same ride height as the e30 Race springs, with a higher spring rate, which would be nice.


I found this:

http://www.turnermotorsport.com/html...Race%20Springs

If that spring fits both e30's and e36's M3's (using the 95 M3 upper perch), that leads me to believe they are interchangeable. And it also sounds like the 95 M3 may have a similar upper perch to the e30, possibly interchangeable and/or different in stack height?

Does anyone have any experience or ideas in swapping out parts between other models?

[nando]

what's the point? it's not like you can't get 2.5" or 2.25" springs and perches in any rate/length you want for $400..

[JGood]

what's the point? it's not like you can't get 2.5" or 2.25" springs and perches in any rate/length you want for $400..

Because I'd like to know? Because going to a coil-over setup may take someone out of a class they'd be in with stock style springs? It doesn't really matter why. Questions like these are why we have e36 steering racks, e90 drop hats, e28 diff ratio's, etc...

If I can get a set of springs that do what I want for $200 and don't have to convert to a $400 coil-over and deal with the involved labor, then I'd prefer to do that.

[nando]

you don't neccesarily need the coilover perches to use 2.5" springs. it was just a suggestion..

[JGood]

you don't neccesarily need the coilover perches to use 2.5" springs. it was just a suggestion..

They work with stock perches?

I figured your post was a "why are you wasting forum space with this thread" deal. Sorry.

[Philo]

Curb weight should be taken into account. E90s are tanks compared to the E30. It's like putting M20 springs on a car with a M42, times ten. Just a thought.

[nando]

Curb weight should be taken into account. E90s are tanks compared to the E30. It's like putting M20 springs on a car with a M42, times ten. Just a thought.

that really depends on their length. none of those rates are really that crazy on an E30, although 1000lbs/inch is pretty stiff for the front.

[JGood]

Curb weight should be taken into account. E90s are tanks compared to the E30. It's like putting M20 springs on a car with a M42, times ten. Just a thought.

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

According to that,

-The stock e30 front spring is 90-100 lb/in, and 14" long.
-The e90 335i sport front springs are 115-130 lb/in, and 13" long.

So if they are the same dimensions, The e90 springs would lower the car a bit and would make it slightly stiffer. Not saying that's what I'm after, but if they are that close stock, then maybe the e90 aftermarket has a good option that would be better then the e30 aftermarket options.

I don't know what the e90 wheel rate is, but I'd assume the front is not much different then an e30.

[nando]

yeah, jeeze, BMW hadn't changed the basic front suspension since the E21? I think they only recently went to a multi-link front?

[JGood]

e46 was the same basic control arm I think, e90 has this, whatever it's called: