US vs Euro E36 M3 suspension difference

[daytonabitch]

It was always my understanding that although the US E36 M3 had less power than the Euro, its chassis tuning etc was the same. Recently however I've seen it written in a contemporary report that the US version had different spring and damper rates -- nothing minor!

Does anybody know definitively what the truth is about this?

My suspension needs freshening, and frankly, if there is a difference I'd rather put on new OEM Euro parts (if available) than take my chances with any aftermarket upgrades.

Thoughts?

[bluptgm3]

You can observe part numbers for the Euro cars, the M3 and the Evo in www.realoem.com. It would be simpler with a VIN for each, but it can be done.
Compare the Strut part number to those of a LWT, a 1995M3 and a 1996+M3. Unfortunately the spring part numbers are not show as a fully loaded Lux version could get fitted with different springs than a ‘slick top’ manual seat car.

You can observe a LWT VIN here -
https://bmwmregistry.com/models.php?id=38


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[daytonabitch]

Good suggestion. I went with realoem and input the VIN for my US car, and for the spring/strut it says ...

Part 31312226987 was found on the following E36 vehicles:

• 3' E36, M3, Convertible, S50, MANUAL, EUR, (BJ91) : Front spring strut/shock absorber
• 3' E36, M3, Convertible, S50, MANUAL, EUR, (BJ92) : Front spring strut/shock absorber
• 3' E36, M3, Coupe, S50, AUTO, USA, (BF03) : Front spring strut/shock absorber
• 3' E36, M3, Coupe, S50, MANUAL, EUR, (BF91) : Front spring strut/shock absorber
• 3' E36, M3, Coupe, S50, MANUAL, EUR, (BF92) : Front spring strut/shock absorber
• 3' E36, M3, Coupe, S50, MANUAL, USA, (BF93) : Front spring strut/shock absorber
• 3' E36, M3, Coupe, S50, MANUAL, EUR, (BF99) : Front spring strut/shock absorber
• 3' E36, M3, Sedan, S50, MANUAL, EUR, (CB91) : Front spring strut/shock absorber
• 3' E36, M3, Sedan, S50, MANUAL, EUR, (CB92) : Front spring strut/shock absorber

So if I'm reading that right, it confirms the Euro and US spring/strut combos were the same.

[bluptgm3]

Note that for at least the US, there are two versions of the struts/shocks for the M3

1995 Strut
LH STRUT 31312226987
RH STRUT 31312226988
REAR SHOCK 33522227794

1996+ Strut
LH STRUT 31312228007
RH STRUT 31312228008
REAR SHOCK 33522228415

This is in addition to the King Pin, FLCA, FLCAB, front Spring (rate) and Strut Mounts differences between 1995M3 and 1996+M3.

Early Euro LH Drive
LH Strut 31312226987
RH Strut 31312226988
Rear Shock 33522227794
Supersedes 33522226989
Superseded by 33522227798 and 33522228415


Late Euro LH Drive
LH Strut 31312228007
RH Strut 31312228008
Rear Shock 33522228415
Supersedes 33522227794, 33522226989, 33522227798

[daytonabitch]

Note that for at least the US, there are two versions of the struts/shocks for the M3

1995 Strut
LH STRUT 31312226987
RH STRUT 31312226988
REAR SHOCK 33522227794

1996+ Strut
LH STRUT 31312228007
RH STRUT 31312228008
REAR SHOCK 33522228415

This is in addition to the King Pin, FLCA, FLCAB, front Spring (rate) and Strut Mounts differences between 1995M3 and 1996+M3.

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THANKS. Mine is a 1995. Do you happen to know what the nature of the differences are between the 95 and the 96+?

[daytonabitch]

Bottom line, did the 96+ changes materially improve the steering feel or handling (other than a revised-ratio rack I believe was also introduced for 96). I have the non-M Z3 rack on my 95. Am I losing out in any way by having the 95 control arms?
Thanks

[bluptgm3]

Am I losing out in any way by having the 95 control arms?

Probably not losing because of the control arms alone. The 1996+M3 FLCA + Centered FLCABs on a 1996+M3 King Pin is stated as replicating the 1995 M3 FLCA + Offset FLCABs on a 1995M3 King Pin ‘caster geometry.’

BimmerWorld used to have a pallet of 1996+M3 King Pins for a package that included the 1996+M3 King Pins, Meyle HD FLCA (E30, E36, 1995M3 geometry) and offset 1995M3 FLCABs.
Not sure if the target market was 1995M3 owners allowing more camber (and more camber at full steering lock) or was it an ‘upgrade’ package for non-“M” cars...or both.
Additionally the 1996+M3 King Pins were at one point in time part of the complete BimmerWorld Roll Center Correction Package.

[BimwadM42]

Bottom line, did the 96+ changes materially improve the steering feel or handling (other than a revised-ratio rack I believe was also introduced for 96). I have the non-M Z3 rack on my 95. Am I losing out in any way by having the 95 control arms?
Thanks

There's nothing special about the 96+ rack, which is common to the rest of the series.

[MParallel]

The EU cast-iron S50 weights considerably more than the US S50/S52 so it makes complete sense the springs/dampers are different.

What would it matter?

[bluptgm3]

The EU cast-iron S50 weights considerably more than the US S50/S52 so it makes complete sense the springs/dampers are different.

What I could find on Weight, the 35 lb difference in US/Euro engine weight might possibly be equal to the difference in weight between power and manual seats in the US market -
Engine kg (lbs)
S50B30 Dual VaNos
151 (333) – EU
S50B30 Single VaNos
135 (298) – US


The 1995 US M3 shares same damper/strut p/n with early Euro M3.
The 1996+ US M3 shares same damper/strut p/n with late Euro M3.

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[daytonabitch]

bluptgm3
thanks for all the good, detailed info. At the end of the day, however, I'm still not clear what was the intent of the changes BMW made for 1996, other than the revised ratio of the steering rack. In particular, was it intended to increase understeer, or reduce it?
Thanks for your patience!

[blckstrm]

bluptgm3
thanks for all the good, detailed info. At the end of the day, however, I'm still not clear what was the intent of the changes BMW made for 1996, other than the revised ratio of the steering rack. In particular, was it intended to increase understeer, or reduce it?
Thanks for your patience!

The tire changes were intended to increase understeer, not the suspension changes.

Who knows why they made the rest of the changes. The only hard change was that the revision reduced caster. Everything else remained the same or was as adjustable as it was before. However, with the change you could now swap strut tops for "track" camber. That works out so nicely I can't help wondering if it was planned.

[bluptgm3]

The tire changes were intended to increase understeer, not the suspension changes.

Who knows why they made the rest of the changes. The only hard change was that the revision reduced caster. Everything else remained the same or was as adjustable as it was before. However, with the change you could now swap strut tops for "track" camber. That works out so nicely I can't help wondering if it was planned.

The 1996+M3 front springs got slightly more stiff (stiffness adds understeer tendency), the upper winding got tighter/smaller requiring a different spring ‘hat’ or upper perch.
Additional changes occurred in ‘sway bars’ (don’t recall diameters) for the 1996+M3s.
edit: added diameters
95 M3 22.5mm front / 19 mm rear
96+M3 23mm front / 20mm rear

The caster inherent (set back) in the 1995M3 Guide Support/Strut Mount was retained in the 1996+M3 Guide Supports, but the strut stands more upright by moving the upper mounting point in the Guide Support outboard.
Standing the strut more upright dramatically raises the front roll center, swapping the strut mounts L<>R, R<>L dramatically drops the roll center.

1995M3
http://3.bp.blogspot.com/-mux2zVZXq2...0/IMG_7420.jpg
1996+M3, swapped L-R. R-L
http://1.bp.blogspot.com/-6XakoeHMRG...0/IMG_7422.jpg

This loss of camber was regained (at least in part) by adding material on the inboard side of the King Pin at the location of the two lower attach fasteners, pivoting the King Pin up/out at the fore-aft facing strut/KP attach point, at the sacrifice of tire-to-strut clearance. (I believe standing the strut more upright causes less camber gain in compression of the strut.) the caster removed by going to a centered FLCAB (from 1995M3 offset FLCAB) was compensated for by positing the King Pin ball Joint further forward in FLCA and redesigning the attach point on the King Pin. (I believe this change corrected a ‘flaw’ in the instant center of the control arm pivot axis caused by using the 1995M3 offset FLCAB.)


For those classes that did not allow camber plates, swapping the Guide Supports L-R, R-L worked nicely in the 1996+M3 chassis for added camber.
The axle centerline was then angled up on the outboard ends to gain back the camber lost to standing the strut more upright.
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[GG///M3]

95 m3’s also had parallel lower rear control arms which made for slightly better handling allowing the rear to have more oversteer where the 96-99’s were not which made them have more understeer .

Front control arm bushings were off centered on 95’s . 96-99’s centered.

95’s handled slightly better in my opinion. With square setup from the factory. 96-99 staggered


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[blckstrm]

The 1996+M3 front springs got slightly more stiff, the upper winding got tighter/smaller requiring a different spring ‘hat’ or upper perch. Additional changes occurred in ‘sway bars’ (don’t recall diameters) for the 1996+M3s.
The caster inherent (set back) in the 1995M3 Guide Support/Strut Mount was retained in the 1996+M3 Guide Supports, but the strut stands more upright by moving the upper mounting point in the Guide Support outboard. This loss of camber was regained (at least in part) by adding material on the inboard side of the King Pin at the location of the two lower attach fasteners, pivoting the King Pin up/out at the fore-aft facing strut/KP attach point, at the sacrifice of tire-to-strut clearance. (I believe standing the strut more upright causes less camber gain in compression of the strut.) the caster removed by going to a centered FLCAB (from 1995M3 offset FLCAB) was compensated for by adding length to the FLCA and redesigning the attach point on the King Pin. (I believe this change corrected a ‘flaw’ in the instant center of the control arm pivot axis caused by using the 1995M3 offset FLCAB.)

For those classes that did not allow camber plates, swapping the Guide Supports L-R, R-L worked nicely in the 1996+M3 chassis for added camber.


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I guess this answers the question of, "who knows why..."

blueptgm3, that's who knows why. In a nutshell - lots of small things impacting some of the suspension dynamics.

I didn't necessarily mean to say that nothing changed, just that of all the small changes that they implemented, there was relatively little from a static setup perspective that changed. Front caster was reduced, front camber was more or less the same, front toe was always adjustable, and all of the rear was always adjustable.

But this is a great explanation of the little improvements (and their trade offs) they carved out here and there.

95 m3’s also had parallel lower rear control arms which made for slightly better handling allowing the rear to have more oversteer where the 96-99’s were not which made them have more understeer .

Front control arm bushings were off centered on 95’s . 96-99’s centered.

95’s handled slightly better in my opinion. With square setup from the factory. 96-99 staggered


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Can you explain this a little more? All the rear suspension parts are the same (subframe, trailing arm, upper and lower control arms) for all E36 M3 (including both generations of both US and Euro cars). What are the lower rear control arms parallel to? The ground? The upper arms? If all the parts are the same, how is the geometry any different?

[MParallel]

^^
Exactly. This is some randomized weird fact thrown in the mix.

Apart from the Compact and Z3’s E30 rear axle, they are all the same.

[daytonabitch]

^^
Exactly. This is some randomized weird fact thrown in the mix.

Apart from the Compact and Z3’s E30 rear axle, they are all the same.

Theoretically, at least, the rear control arms could have different geometry if the mounting points changed, even if the arm itself was unchanged.

[bluptgm3]

All the rear suspension parts are the same (subframe, trailing arm, upper and lower control arms) for all E36 M3 (including both generations of both US and Euro cars).

Theoretically, at least, the rear control arms could have different geometry if the mounting points changed, even if the arm itself was unchanged.

Ya, that was my impression also, but then I remembered seeing a part number difference in the RTA part numbers, and no one seems talk about this.

The 1996+M3 got solid Ball Joints in the rear outer upper and rear outer lower positions while 1995M3 got a solid upper BJ and a Rubber Mounting in the lower position.
The 1996+M3 solid BJ part 33306852895 fits the 1995M3 RTA in both the outer upr and outer lwr locations.

Anyone know what changed on the RTA?

Part numbers of rear suspension major components -
1995M3
Rear Axle Carrier 33312227800
Upper Wishbone - Left 33321095555
Upper Wishbone - Right 33321095556
Lower Wishbone 33326770813
Trailing Arm - Left 33322227077
Trailing Arm - Right 33322227078
Ball Joint (upr) 33326775551
Rubber Mounting (lwr) 33326771828

1996+M3
Rear Axle Carrier 33312227800
Upper Wishbone - Left 33321095555
Upper Wishbone - Right 33321095556
Lower Wishbone 33326770813
Trailing Arm - Left 33322227985
Trailing Arm - Right 33322227986
Ball Joint (upr) 33306852895
replaces 33326775551
Ball Joint (lwr ) 33306852895

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[blckstrm]

Theoretically, at least, the rear control arms could have different geometry if the mounting points changed, even if the arm itself was unchanged.

That's why I included the subframe and trailing arm along with the control arms - they include both the in board (subframe) and outboard (trailing arm) mounting points. I thought all the part numbers were the same, but the trailing arms have a different part number.

Ya, that was my impression also, but then I remembered seeing a part number difference in the RTA part numbers, and no one seems talk about this.

The 1996+M3 got rear outer upper and rear outer lower solid Ball Joints while 1995M3 got a solid upper BJ and a Rubber Mounting in the lower position.
The 1996+M3 part 33306852895 fits the 1995M3 RTA in both the upr and lwr locations.

Anyone know what changed on the RTA?

Part numbers of rear suspension major components -
1995M3
Rear Axle Carrier 33312227800
Upper Wishbone - Left 33321095555
Upper Wishbone - Right 33321095556
Lower Wishbone 33326770813
Trailing Arm - Left 33322227077
Trailing Arm - Left 33322227078
Ball Joint (upr) 33326775551
Rubber Mounting (lwr) 33326771828

1996+M3
Rear Axle Carrier 33312227800
Upper Wishbone - Left 33321095555
Upper Wishbone - Right 33321095556
Lower Wishbone 33326770813
Trailing Arm - Left 33322227985
Trailing Arm - Right 33322227986
Ball Joint (upr) 33306852895
replaces 33326775551
Ball Joint (lwr ) 33306852895

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When I checked real OEM I must have clicked on the wrong part. I wonder if it was just the ball joint VS bushing change. Given the control arms are the same, the camber is adjustable, and you only have so much room to work with, at best the change would be a little higher or lower in the arc of the lower arm, and would either slightly accelerate or decelerate the camber gain on compression.

If the 95 trailing arm is set up so the lower control arms were parallel to each other and the ground, 95s would gain less camber in compression than a 96+ car where the lower arms are angled downward.

Think of a clock, and the arm moves from 3:00 to 2:00 - that 2:00 position is closer to the clock center line, so the bottom attachment point is moving inward on a 95 car. Not as fast as the top attachment point on the trailing arm, but moving inward. On a 96+ car you're moving from 4:00 to 3:00 - the lower connection point is moving away from the center of the clock, while the top point is moving in. In theory that should give you a lot more camber gain.

If you assume BMW revised the suspension to add camber faster because the car could make better traction, then this would all make sense. Improving rear traction would obviously move the understeer / oversteer balance toward the front.

All that said, I doubt the intention was to dial in more understeer. It was probably more of a second - or third - order impact.

[Edit] I found a picture of the 95 trailing arm, and the lower control arm mounting point is definitely an inch or two higher than a 96+ arm.

Guess it puts that to rest.

I don't think I'd make understeer / oversteer the basis of my decision - you can go 0 toe and get PLENTY of oversteer in either car...

[GG///M3]

That's why I included the subframe and trailing arm along with the control arms - they include both the in board (subframe) and outboard (trailing arm) mounting points. I thought all the part numbers were the same, but the trailing arms have a different part number.



When I checked real OEM I must have clicked on the wrong part. I wonder if it was just the ball joint VS bushing change. Given the control arms are the same, the camber is adjustable, and you only have so much room to work with, at best the change would be a little higher or lower in the arc of the lower arm, and would either slightly accelerate or decelerate the camber gain on compression.

If the 95 trailing arm is set up so the lower control arms were parallel to each other and the ground, 95s would gain less camber in compression than a 96+ car where the lower arms are angled downward.

Think of a clock, and the arm moves from 3:00 to 2:00 - that 2:00 position is closer to the clock center line, so the bottom attachment point is moving inward on a 95 car. Not as fast as the top attachment point on the trailing arm, but moving inward. On a 96+ car you're moving from 4:00 to 3:00 - the lower connection point is moving away from the center of the clock, while the top point is moving in. In theory that should give you a lot more camber gain.

If you assume BMW revised the suspension to add camber faster because the car could make better traction, then this would all make sense. Improving rear traction would obviously move the understeer / oversteer balance toward the front.

All that said, I doubt the intention was to dial in more understeer. It was probably more of a second - or third - order impact.

[Edit] I found a picture of the 95 trailing arm, and the lower control arm mounting point is definitely an inch or two higher than a 96+ arm.

Guess it puts that to rest.

I don't think I'd make understeer / oversteer the basis of my decision - you can go 0 toe and get PLENTY of oversteer in either car...

Many have said it was to dial in more understeer when it was done(magazines, and those tracking both) . Easily corrected with adjustable lower rear control arms , and a square setup.


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[bluptgm3]

I wonder if it was just the ball joint VS bushing change.

Ya I looked for that also, however the diagram does not appear to include the BJ/Rubber Mount items in the RTA part.

Given the control arms are the same, the camber is adjustable, and you only have so much room to work with, at best the change would be a little higher or lower in the arc of the lower arm, and would either slightly accelerate or decelerate the camber gain on compression.

If the 95 trailing arm is set up so the lower control arms were parallel to each other and the ground, 95s would gain less camber in compression than a 96+ car where the lower arms are angled downward.

If you assume BMW revised the suspension to add camber faster because the car could make better traction, then this would all make sense. Improving rear traction would obviously move the understeer / oversteer balance toward the front.

[Edit] I found a picture of the 95 trailing arm, and the lower control arm mounting point is definitely an inch or two higher than a 96+ arm.

That would be great if you could share the images, I poked around a bit but was unable to locate them, both 1995M3 RTA and 1996+M3 RTA.

Many have said it was to dial in more understeer when it was done. Easily corrected with adjustable lower rear control arms, and a square setup.

While I agree, the static camber can be adjusted with aftermarket adjustable lower control arms, it is the dynamic changes that are inherent in the pickup points of the hub that I’d like to understand.
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[blckstrm]

Many have said it was to dial in more understeer when it was done(magazines, and those tracking both) . Easily corrected with adjustable lower rear control arms , and a square setup.


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I doubt it was done just to disk in more understeer. There are WAY easier ways to increase understeer - and BMW HATES changing parts for no reason. And auto journalists aren't exactly engineers.

Now, if understeer was a knock-on effect and was also something they wanted to add, that explains why they didn't add a little more camber at the front to balance it back out.

But again, they didn't give it less grip in front, they gave it more grip in the rear.

As far as getting rid of it, I don't see the reason for adjustable rear arms - the arms were always the same.

But square tires and a little more front camber should leave anyone pretty neutral, and you can fine tune with toe.

But geez, engineer or not - journalists should have been blaming the understeer on the tire change.

[blckstrm]

I had to take a picture of my car for the 96+.

Here's the 95 trailing arm I found on ebay this afternoon:

Screenshot_20200719-192848_eBay.jpg

And here's my car (a 96+ arm):

20200719_193605.jpg

It seems different enough to make at least some difference.

[MParallel]

I would have to put my 328i and (EU) M3 side by side to check for any difference besides some different spacing for the brake caliper.

[blckstrm]

I would have to put my 328i and (EU) M3 side by side to check for any difference besides some different spacing for the brake caliper.

M3s had different trailing arms than the stock cars. And even if not, both your cars are post-LCI, right?