Differences Between Non-M and M3 Suspension

Here is some info and pictures about both setups.


Front struts: Interchangeable only with appropriate strut bearing assembly, bump stops(if used), and dust boots(if used).
Strut bearings: Interchangeable only with appropriate strut and removal of factory alignment pin. NOTE: Changes alignment range.
Rear dampers and mounting bushings: Interchangeable
Front springs and spring pads: Interchangeable
Rear springs and spring pads: Interchangeable
Front anti-sway bars: Interchangeable only with appropriate bushings and brackets
Rear anti-sway bars: Not interchangeable (forum supplied information; reasonable to believe because of dimensionally different rear subframes, differentials, and difference in spare tire well)


Strut assembly pieces in order:

Stock Non-M:


Stock M3:




The M3 strut bearings are mirrored left to right and have an offset strut attachment hole that changes alignment between the M3 and non-M. The non-M strut bearings have a concentric attachment hole and are identical left and right. The M3 strut bearings can be clocked or swapped left to right to change the alignment range; the factory alignment pin must be unscrewed to do so. I am not sure of any long term integrity or accelerated wear problems caused by this, but I have observed no ill effects on two non-Ms with modified position M3 strut bearings.

Original M3 position strut bearing orientation on left strut; reducing camber and increasing caster compared to non-M:


M3 strut bearing rotated 120 degrees clockwise from original position; decreases camber and decreases caster compared to non-M, increases camber and decreases caster compared to original:


M3 strut bearing rotated 240 degrease clockwise from original postion; increases camber and increases caster compared to non-M, increases camber and decreases caster compared to original:


Underside of M3 strut bearings showing they have substantially more material, are designed for much greater rigidity, and a larger, stronger, sealed bearing is used, greatly increasing service life and reducing chances of strut tower mushrooming with the downside being roughly $90 more expensive per strut bearing:




Non-M struts are partially compressed at rest position, fluid can be heard if shaken, and easier to compress, strongly suggesting a low-pressure twin-tube design. M3 struts are fully extended at rest, no fluid can be heard if shaken, and are harder to compress, strongly suggesting a high-pressure mono-tube design.

Non-M left, M3 right


The threaded shaft length above the taper is why non-M(left) and M3(right) struts must be used with the appropriate strut bearings and vice versa:



Appearance, ride, and handling of M3 suspension on a non-M: M3 suspension on a non-M looks similar to non-M sport suspension in terms of ride height, but spring rates are considerably higher and damping is much greater as well. There is no noticeable lift in the front relative to the rear as rumored by some by running M3 suspension on a non-M. The ride feels very similar to an M3 meaning much more road feedback and the car follows the road more sharply. I haven't driven any of these cars hard enough to comment on at-the-limit handling.


*Everything here is through actual experience from working on and driving multiple E46 unless stated. This only info only applies to US market M3 and rear wheel drive non-M.

All of the above confirmed (from experience with a couple of cars).

I've also kept non-M front suspension (KW V2) on a non-M and swapped in M3 front king pins, control arms, bearings, brakes, and tie rods. Caster is within non-M spec.

I'm also running fine w/ m suspension on non-m. Found out about the taper difference on the front struts the hard way

I don't know much about the e46 M3 cuz I never own or driven one (always wanted one but bought the e90 M3 instead) but I know a member who actually knows his M3 and that is Alex323ci. Alex and I might not agree on certain issues but when it comes to the M3 it seems like he knows his stuff (just giving credit where credit is due).

anyhow...this is what Alex323ci wrote regarding retrofitting M3 suspension into the non M

Originally Posted by Alex323Ci

I'm pretty sure if you have a non-m and only the rear M3 swapped over you'll want the non-m parts. M3 shocks and springs are tuned/valved for the M3 and actually tall. So some aftermarket Sport version of the non-M shocks/springs will be best.

Swaybars, I forget if the M fronts even fit correctly by the endlinks on non-m. and I don't recall if the rear M3 would take a different non-M designed bar. Swaybars you may have to mix. SLO_Town has a write up/thread on oem swaybars that may give options/answers.

I'm still surprised this is something that goes on. Is it people trying to save money by buying the M3 pieces?

Originally Posted by 323ci newbie

I'm still surprised this is something that goes on. Is it people trying to save money by buying the M3 pieces?

It's information to give people more options for their car's suspension.

Now neither the M3 nor non-M people need to pass up a good deal on a set of Bilstein coilovers because they were made for the "other" model, people will know what the exact differences are instead of figuring it out after taking the struts off the car, it's a nice picture guide in case your set of struts didn't come instructions for the order of parts, etc...

Originally Posted by 323ci newbie

I'm still surprised this is something that goes on. Is it people trying to save money by buying the M3 pieces?

In my case I had stock over 80k and they were going noticeably squishy; wanted Bikstein coilovers but didn't have the loot and found a set of M3 parts that were taken out after only several years use by someone building a track car (purchased from respectable shop that builds many race cars). Cost was very low even with labor and needing to buy some components that Iacked (top hats specifically). Outcome was a better handling 330 than it had ever been (I bought as second owner at 50k).

Now I lucked into a cheap set of Bilstein PSS and Miles did the install, and while some decry drop I'm very pleased indeed and the handling is planted.

Spent afternoon lightly rolling fenders.

A big thanks to Mkodama for all the hard work on car and providing facts here as some chose to insult and condescend m3 rationale endlessly despite lack of factual basis. I had checked on viability of swap with a longtime BMW technician who is a friend if a friend and he had said it was fine... But in the intarnetz some prefer their own idealogical bluster over objective facts.

Pics of my car from oem to m3 to PSS:

Keep this on topic.

Thanks for this info! I'm due for struts and was considering running stock m3 struts up front, I also like the fact that the m3 top hats give more alignment range

And knowing is half the battle!

the BC's I have on my car are made for M3. so, yeah they work fine.

Great information! Thanks!

Nice tid bit of info compromised for comparison.

According to BMW ///M, the E46 M3 has "twin-tube gas-pressure shock absorbers with hollow piston rods to minimize inertia and mass". Which is contrary to your thoughts it's a "high pressure mono tube design".

Of note I would like to point out is that the M3 ZCP (and all E46 M3s after 12/04) received revised springs and shocks. These specs aren't exact but are accepted to be taller and softer than earlier M3 springs/dampers.

As for the M3 strut bearings "..reducing the chances of strut tower mushrooming". Perhaps some since it's offset, but I wouldn't suggest much. Although the M3 Strut bearing/mount appears to have more surface area, it is rounded down on the edges. The amount that touches the top tower is almost the same. M3s have strut tower mushrooming and cracking just like non-Ms. This is mostly on the early M3s that didn't have the factory M3 strut brace installed. I would not expect any less mushrooming or cracking by just using M3 strut mounts. But they are suppose to be a tad more isolated.

Gents,

You seem to have tried all possible variations. Kudos !

Can you provide info on final camber and caster values in the best position.
To me, this would be highest (biggest -ve number) camber setting.

I want to push more camber into the front of the car but camber plates are not really an option with the state of our roads.

I have used RE fixed camber plates but they are not aggressive enough and TMS fixed camber plates are never is stock.

This solution may be a winner giving me the aggressive alignment I want with beefier struts.

Rick

^^+1. Will M3 strut bearings on a non-m change the caster adjustment range to be similar to the E46 M3?

Originally Posted by ZHP6

^^+1. Will M3 strut bearings on a non-m change the caster adjustment range to be similar to the E46 M3?

Just changing the strut bearings won't get you the same adjustment range as the M3. The M3 has different control arms and kingpins, altering alignment.

Originally Posted by mkodama

Just changing the strut bearings won't get you the same adjustment range as the M3. The M3 has different control arms and kingpins, altering alignment.

Is there a way to swap those in as well, or do you need the E46 M3 subframe? I'm trying to figure out if it's possible to get at least 7 degrees of caster with camber plates and a few mods.

Originally Posted by ZHP6

Is there a way to swap those in as well, or do you need the E46 M3 subframe? I'm trying to figure out if it's possible to get at least 7 degrees of caster with camber plates and a few mods.

Front subframe and suspension mounting points are all the same. You can swap everything over.

Originally Posted by mkodama

Front subframe and suspension mounting points are all the same. You can swap everything over.

That would give you the E46 M3 adjustment range then, correct? If you have the entire subframe, will a non-m still sit the same height as a non-sport non-m?

Originally Posted by ZHP6

Is there a way to swap those in as well, or do you need the E46 M3 subframe? I'm trying to figure out if it's possible to get at least 7 degrees of caster with camber plates and a few mods.

I've done exactly that. Front subframe was left stock (it's already the same part number as the M3).
http://forum.e46fanatics.com/showpos...&postcount=487