Can someone please explain any differences between the IC & IS suspension components?

[Cobra Jet]

Hi folks,

I have a 1991 318ic and just need a little verification or help on some parts... I've tried searching and there are not any real definitive threads on multiple BMW sites/forums about the actual (or factual) differences between the E30 318ic and 318is suspension components...

From what I have deduced so far is that the following components are exactly the same (including part #'s) and interchangeability between the IC & IS:

front brake rotors
front brake calipers (and pads)
front brake hoses
front wheel hub assemblies
front spindle nuts
front tie rod assemblies (both inner/outer)
front strut mounts
front bump stops
front control arms
front control arm ball joints
front sway bar end links
front "lollipops"
rear control arms
rear hubs
rear axle nut
rear wheel bearings
rear brake rotors
rear brake calipers (and pads)
rear brake hoses
rear sway bar end links
rear shock mounts
steering rack



What I cannot seem to get a real confirmation on, as far as compatibility, are the following parts:

front springs
rear springs
front strut inserts
rear shocks



What are the major differences of those parts (springs/struts/shocks) between the IC & IS??

Does anyone know the actual factory spring rates & heights for an IC vs IS?

Does anyone know if the standard 318is struts & shocks will work for a 318ic?

What is the diameter of the front strut housing on a 91 318, is it 51mm for a 91 318ic and is this the same for a 318is?

Can a set of E30 M3 springs be used on a 318ic?



I'm trying to price out front struts & rear shocks for my 91 318ic and some sites don't list any "ic specific" parts, while others do... the same holds true for aftermarket spring sets....

Please Help!






(oh yea, the same holds true if one is searching for compatibility between the same parts mentioned above for the E30 325ic vs the 325is)

[NC325iC]

IC springs are stiffer in the rear to support the extra weigh on the back wheels with the top down. dont know about the other ones.

[thereisnoyun]

if you look on the bentley, there are a ton of different springs for the same car. They also use springs across the dfiferent model cars for lowering per bmw spec.

[nando]

other than being slightly stiffer, there's no real reason why springs/shocks from any E30 won't work with your car. They will all fit, they just might not be ideal.

[Cobra Jet]

So, essentially what some of you are saying is, I *can* use front struts and rear shocks for a 318is on my 318ic?

I was looking at a set of Bilstein Tourings for the front & rear, however, if I look by using my specific model, the same shocks/struts are not listed - but if I use the same year vehicle and use a 318is instead of 318ic designation for model, the Bilstein Tourings are listed.... makes absolutely no sense, especially IF the shocks & struts will install and fit either vehicle...

Any other comments/opinions?

Thx!

[nando]

yes they will fit

the reason they aren't listed for your car is because it weighs more and the distribution of that weight is different. So they sometimes adjust that balance to suit your car.. however I'm not even sure there is a real difference between any of the E30 struts/shocks, except for maybe the front of an ix and the M3. You would have to cross reference part #s to find that out.

if there are just bilstein tourings with stock springs, they will be fine.