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Differences Between Non-M and M3 Suspension

157K views 100 replies 42 participants last post by  A930rocket 
#1 · (Edited)
Here is some info and pictures about both setups.


Struts, front: Interchangeable only with appropriate strut bearing assembly, bump stops(if used), and dust boots(if used).
Strut mounts, front: Interchangeable only with appropriate strut and removal of factory alignment pin. NOTE: Changes alignment range.
Shock and mount, rear: Interchangeable
Springs, front: Interchangeable only with appropriate strut mount assembly or modification of spring.
Springs, rear: Interchangeable
Anti-sway bars, front: Interchangeable only with appropriate bushings and brackets
Anti-sway bar, rear: 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. M3 struts are fully extended at rest, no fluid can be heard if shaken, and are harder to compress.

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 people. 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.
 
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#2 ·
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.
 
#4 ·
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

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.
 
#6 ·
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...
 
#13 ·
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". :dunno:

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.
 
#14 ·
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
 
#27 ·
You've got me curious. Do you have a link to the specs pages?
 
#28 ·
i figured you wouldn't believe me.
last line of the E46 M3 FRONT SUSPENSION SPECS

 
#35 · (Edited)
In that last picture of the strut bearing:
Rotated 240 degrees clockwise from original, it seems to give the highest camber and caster when used on non M.

Has anyone set it like this and performed a wheel alignment ?

What is the measurement for camber and caster ?

Visually I would guess around -3 degrees camber.

Anyone have data or a more educated guess ?
 
#40 · (Edited)
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."
I know for a fact that non-M-shock-absorbers are twin-tube-design. However - the OEM-Sachs-shocks on my 330 (M-package) did fully extend in resting position (even after 5 years / 90.000km). Even the rear ones that were leaking oil did fully extend - indicating that there was still pressure inside.

Same goes for my brand new Bilstein B4 replacement shock absorbers which are listed as twin-tube-design - they fully extend - all by themselves. If your E46 Sachs/Bilstein shocks dont fully extend its likely they are worn out/shot/dead. I know - there are cases were brand new twin-tube-shocks dont fully extend but the twin-tube Sachs/Bilstein E46 shocks do!

Note: twin design shocks break down slowly. They even work (kind of) when they are in the process of failing. This is why a lot of people dont notice that their shocks are gone. It usually happens so slowly that they get used to feel. Mono-tubes usually last longer than twin-tubes but when they fail -> you know immediately :)

BTW - if you look up the E46 M3 shocks in the Bilstein catalog you will see that the B4 replacement shocks are listed as twin-tube-design as well. That of course does not prove that the OEM M3 shocks (I guess Sachs) are twin-tube-design but its an indication.
 
#51 ·
I know for a fact that non-M-shock-absorbers are twin-tube-design.
yes i already posted that back in jan in post #13. but looks like the OP finally fixed this and edited it out now several months later. :hi:

and how to modify M3 springs to fit non-M strut mounts: http://forum.e46fanatics.com/showthread.php?t=1000631
that has to be the worst thing you can do to a set of springs. cutting a section of coil out that's not a "dead section" is like changing the whole spring rate and matched set of springs. that's Honda stuff. Don't cut your coils in your springs. :nono:
 
#43 · (Edited)
As a chassis engineer, I can triple confirm that both M and non-M struts are twin tubes. The non-M pictured has a rebound spring, which is an internal spring that acts against the normal coil spring to increase roll stiffness. In the resting state, the spring is extended, which holds the rod in the position you see in the picture. If you grab the rod and pull really hard, you would compress the spring and you'd be able to pull the rod out almost as far as the M3 strut.

Rebound springs act sort of like a stiffer stabilizer bar, with some key differences:

  1. They also reduce body float and prevent the suspension from topping when you hit a large pothole, which helps prevent wheel and tire damage
  2. They still work when the wheels are moving vertically together
  3. They maintain full independence of the left and right suspension
 
#45 ·
okay guys i have a question... I lowered my car(330i) yesterday on tein-s tech springs. after installing the tein springs, i found out that all 4 corners shocks/struts were blown. My car was sitting really low (about 2 inch drop). The mechanic said that my car was sitting really low because my shocks/springs were out. I can't afford koni/bilsteins shocks atm and there is someone local to me selling a full set of m3 suspension. From research, i found out i can directly swap out the rear shocks of an m3 to non-m but how would i go about doing the front. Would i still be able to use my tein (non-m) springs on m3 front struts and top hats? What else would i need to replace and/or tweak. any info would help. thanks guys!
 
#46 ·
1) I've already addressed the shocks/struts being blown. I've told the forum over and over that your stock struts/shocks, if original OE, are blown after 40k miles.

2) The used M3 stuff you're going to buy will also be considerably reduced in capability if not severely blown.

3) As discussed, it's not a direct swap. You'd need M3 front strut mounts which would blow your budget.

My advice to you is to save up for stuff you really want instead of installing junk on your car then spending even more money and time later installing the stuff you really want.

Don't nickel and dime things. Do it right the first time. GL! :thumbsup:
 
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