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      08-10-2019, 01:26 PM   #23
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Quote:
Originally Posted by Dackelone View Post
The main reason to use both M3 suspension links is bc the bushings are much more robust and don't allow for any deflection. I think this is what "fixed" my bumpsteer from the rear suspension. Btw... I already had M3 rear subframe bushings before any of these parts were installed.

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Yeah, I was just saying part #17 actually has the same bushings as the OEM arm. Arm #18 is the one that has the bearing upgrade.

Still, even with the same bushings, the M3 arm #17 still looks way cooler and is a little lighter.
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      08-10-2019, 05:23 PM   #24
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Check out the OE vs M3 control arms thread. There's a new product in the works for toe arms that would allow you to go full spherical (in that part) with no deflection or Group N bushings for minimal deflection plus some spring rate contribution....

OE vs M3 Rear Suspension Arms
https://www.1addicts.com/forums/show....php?t=1079383



Stay tuned!
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      08-10-2019, 07:16 PM   #25
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Quote:
Originally Posted by duder13 View Post
Yeah, I was just saying part #17 actually has the same bushings as the OEM arm. Arm #18 is the one that has the bearing upgrade.

Still, even with the same bushings, the M3 arm #17 still looks way cooler and is a little lighter.

???

The factory 135i rear suspension parts are cheap stamped steel with a steel insert that sits inside a soft rubber bushing.

The M3/1M bits are light alloy arms with a hard bearing pressed into the arm. The black rubber is quite hard compared to the 135i bits.

The differences are night and day.




Some pics for reference, from the interwebs....
Name:  1 M3 Exploded View.jpg
Views: 458
Size:  89.1 KB

Name:  e9x_bush.jpg
Views: 452
Size:  70.5 KB

non M and ///M rear suspension...
Name:  E90M3RearSuspension.jpg
Views: 448
Size:  57.7 KB

///M rear suspension...
Name:  IMG_83441-1024x768.jpg
Views: 446
Size:  128.2 KB

stock 135i suspension...
Name:  inv_015622__16681.1523310721.jpg
Views: 444
Size:  63.2 KB
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      08-10-2019, 08:42 PM   #26
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Quote:
Originally Posted by Dackelone View Post
???

The factory 135i rear suspension parts are cheap stamped steel with a steel insert that sits inside a soft rubber bushing.

The M3/1M bits are light alloy arms with a hard bearing pressed into the arm. The black rubber is quite hard compared to the 135i bits.

The differences are night and day.




Some pics for reference, from the interwebs....
Attachment 2118068

Attachment 2118064

non M and ///M rear suspension...
Attachment 2118065

///M rear suspension...
Attachment 2118066

stock 135i suspension...
Attachment 2118067
Oh, I guess you haven’t seen the classic fe1rx thread. Check it out below. He tested all of it, and despite being made of steel, the OEM arms have the same strength as the aluminum ones, albeit uglier and a little heavier. The bushings/bearings of the the 1M wishbone (upper) arms (#17) are also the same as OEM, so, from a performance perspective, the guide rods (#18) and toe arms are the only things that need to be upgraded, weight not withstanding.

You can even see in your pic above that the OEM wishbone arms have a bearing on one side and bushing in the other.

https://www.1addicts.com/forums/show....php?t=1079383

Last edited by duder13; 08-10-2019 at 08:49 PM..
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      05-24-2020, 11:03 PM   #27
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Those roll centre change and camber gain/loss graphs are fantastic, particularly on the front end. The interplay between a linear loss in camber and an accelerating roll center drop (and its affect on weight transfer front to rear) would be good to understand in depth - or just take home that controlling roll is important for predictable high speed cornering behaviour.
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      06-18-2020, 04:20 PM   #28
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Quote:
Originally Posted by fe1rx View Post
The principal dimensions for the chassis related to the front suspension are shown in the figure below. For design purposes, front camber of -3.0° was selected, and a caster angle of 7.3°. These settings establish the strut top position for design purposes, which is assumed to be adjustable by means of a camber/caster plate.

Attachment 2031189

To complete the picture up front we also need the geometry of the steering knuckle, strut and suspension arms.

The true length of the suspension arms (ball-to-ball) requires some careful setup to measure.

Attachment 2031190

Attachment 2031191

Measuring the steering knuckle must be done with particular precision due to the close proximity of the various pivot points. This required disassembly of the steering knuckle, installation of spherical targets (recovered from actual suspension components to ensure proper geometry).

Attachment 2031192

Attachment 2031193

A spherical target makes it easy to find the exact centre of rotation of each pivot location. I used a dial indicator to centre on each ball, and a digital readout on the vertical mill to find the location of each ball in x-x-z space. Desired accuracy is ±0.2 mm.

Attachment 2031194

The front strut has its own coordinate system (as specified in SusProg3D), centered on the wheel hub mounting surface. The assembly is measured with no camber or caster.

Attachment 2031195

With this data we can create both a CAD model and a SusProg3D model to visualize and characterize the suspension. The dual ball joint design of our front suspensions actually steers about a virtual lower ball joint that moves continuously with respect to the knuckle during both steering and vertical motion. Using CAD to find the virtual ball joint location for the one design condition is difficult but not impossible. Using it to solve for the location at a variety of suspension height is definitely impractical. Luckily SusProg3D handles this task with ease. Having both the CAD and SusProg3D models is useful to provide a cross check for logical consistency.

Attachment 2031196

To complete the model, the following additional data is required:

Initial Wheel and Tire data: I chose 18” x 8.5” ET45 wheels with tires with a rolling radius of 312 mm. These can easily be changed later in the SusProg3D model if desired.

Initial ride height: I chose 640 mm from ground to wheel well datum (corresponding to 328 mm wheel centre plus 312 mm rolling radius). Again once the model is established, ride height can be altered at will.
fe1rx, firstly a massive thank you for sharing so much of your hard work with us! I'm using your data to create a CAD model of my E91 suspension - I don't have the time, facilities, tools or even patience to get all these measurements myself, and your work is clearly so much better than mine could be.

Not meaning to look a gift horse in the mouth, I think I've found an error somewhere in your front suspension measurements:

Firstly, entering the coordinates for the front upright/strut into cad, I find that the angle between the strut and the hub flange is actually 8.38deg. I've gone through the coordinates multiple times, but can't find my error.

Inserting this component into an assembly with the front arms and chassis pickup points, along with the -3deg of camber, I find that the top strut point is some 21.25mm shy of the chassis coordinate in that location. The strut top point is nearly vertically below the chassis point; I aligned the plane of the front axle/strut with the chassis point, so that the strut/hub was constrained from rotating. I get 6.95deg caster. These measurements assume 0deg toe, though that can't account for all the discrepancy.

I'm sure the issue is just a typo somewhere, otherwise the diagrams you've posted would look significantly different, but I thought I should share at least this part of my findings in case it helps you or anyone else fix an error.

EDIT: I think the error is in the strut top coordinate, in the hub/strut model; I think this should be 0.0, 222.1, 442.5 instead of 0.0, 222.1, 422.5.

Last edited by Tambohamilton; 06-19-2020 at 12:02 PM..
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      06-19-2020, 12:44 PM   #29
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Quote:
Originally Posted by Tambohamilton View Post
fe1rx, firstly a massive thank you for sharing so much of your hard work with us! I'm using your data to create a CAD model of my E91 suspension - I don't have the time, facilities, tools or even patience to get all these measurements myself, and your work is clearly so much better than mine could be.

Not meaning to look a gift horse in the mouth, I think I've found an error somewhere in your front suspension measurements:

Firstly, entering the coordinates for the front upright/strut into cad, I find that the angle between the strut and the hub flange is actually 8.38deg. I've gone through the coordinates multiple times, but can't find my error.

Inserting this component into an assembly with the front arms and chassis pickup points, along with the -3deg of camber, I find that the top strut point is some 21.25mm shy of the chassis coordinate in that location. The strut top point is nearly vertically below the chassis point; I aligned the plane of the front axle/strut with the chassis point, so that the strut/hub was constrained from rotating. I get 6.95deg caster. These measurements assume 0deg toe, though that can't account for all the discrepancy.

I'm sure the issue is just a typo somewhere, otherwise the diagrams you've posted would look significantly different, but I thought I should share at least this part of my findings in case it helps you or anyone else fix an error.

EDIT: I think the error is in the strut top coordinate, in the hub/strut model; I think this should be 0.0, 222.1, 442.5 instead of 0.0, 222.1, 422.5.
Good catch! You are right, the strut top at ride height should be 442.5. Those balloons with the dimensions were populated manually so it as a typo. Thankfully when I entered the dimensions into SusProg3D I got them correct.

I really appreciate your double checking my work though.
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      06-20-2020, 07:51 AM   #30
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Good good! I'm sure you would also have found it, if you'd used the wrong numbers yourself...

Next question; that coordinate for the top of the strut - where is that in relation to the top flange of the strut mount/camber plate, where it bolts up to the chassis, please? I assume the coordinates refer to the centre point of the rubber bushing where the strut attaches to the mount, but in order to get useful geometry for my purposes I need to know where that is relative to the chassis attachment.

I've got a functional model in CAD now, but I just need to know that one bit of information in order to transpose it for the e90/1. (And I'm just going to change the rear ride height by the same amount as the front, and pretend that's accurate).

Thanks!
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      06-20-2020, 11:30 AM   #31
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Quote:
Originally Posted by Tambohamilton View Post
Good good! I'm sure you would also have found it, if you'd used the wrong numbers yourself...

Next question; that coordinate for the top of the strut - where is that in relation to the top flange of the strut mount/camber plate, where it bolts up to the chassis, please? I assume the coordinates refer to the centre point of the rubber bushing where the strut attaches to the mount, but in order to get useful geometry for my purposes I need to know where that is relative to the chassis attachment.

I've got a functional model in CAD now, but I just need to know that one bit of information in order to transpose it for the e90/1. (And I'm just going to change the rear ride height by the same amount as the front, and pretend that's accurate).

Thanks!
I have revised the strut image to show the strut and spring compressed, and added the location of the mounting flange, which should clarify that the top dimension you were asking about is centred on the rubber bushing a you assumed. Note that my geometry includes a 10 mm spacer where the strut buts up against the upright. You have probably noted that I added this to increase my ride height while eliminating the need to add spring preload. Also, I am using a custom camber plate (based on a Ground Control street plate, but taller and angled to align the spring axis with the strut axis), so the dimensions I have provided are unique to my setup. The basic strut dimensions are Ohlins, of course. To the extent your setup differs, you will need to adjust your strut and camber plate / top fitting geometries. If you are using the original strut top fitting, note that the rubber deflection of this part under static loading is significant (about 5 mm) and needs to be accounted for too.

Name:  Front Strut Geometry.jpg
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      06-20-2020, 04:39 PM   #32
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Thanks a lot! That's super helpful.

Unfortunately I'm getting lost now.

I've measured my struts, top mount flange (@ chassis) to the top datum of the knuckle; 466 at full droop; 367.6 at ride height.
Using a measurement from your Ohlins install thread (372 top mount flange to knuckle datum @ 326mm ride height; 2mm lower than these geometry measurements), the top mount flange to knuckle datum for this setup should be 373.92.
Now, my car has stock non-sport springs, koni special active struts, and Xd top mounts...I seriously doubt it's lower (367.6 vs 373.9) than your track setup! I thought I could just plug in your coordinates, adjust based on strut length @ ride height, and arrive at my geometry...but it's not worked out.

I don't really think that the wheel arch/fender reference will be the same on both chassis, but at this stage I think I might have to use it. Ride height on mine is 354; 26mm higher than yours to the arch...that sounds like the right ballpark. And I doubt that the fenders are as much as 30mm-ish higher relative to the suspension points on the e90/1. Come to think of it, how sure am I that all the suspension points transfer 100% between the two cars?

Time for me to take stock, and figure out a better way to get my model set up

All this just for some spreadsheet fun in the evenings, while I contemplate shoehorning M3 springs into the front of my car

Last edited by Tambohamilton; 06-20-2020 at 04:45 PM..
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      06-26-2020, 12:44 PM   #33
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Eventually figured I could just measure the Z height of a reference point front in each of the front and rear (wishbone inner end at the front, and camber arm inner end at the rear). I measured from a string line under the tyres, with the wheels up on a couple of 1" boards just to make sure the string line was off the ground.

At some point I'll need to go back through the whole model and check it all, but for now I'm content that it's giving me reasonable figures. Magic number spreadsheet is coming together now...just a few bumps to iron out.

Thanks again, fe1rx for the data!
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      06-26-2020, 01:46 PM   #34
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Quote:
Originally Posted by Tambohamilton View Post
Eventually figured I could just measure the Z height of a reference point front in each of the front and rear (wishbone inner end at the front, and camber arm inner end at the rear). I measured from a string line under the tyres, with the wheels up on a couple of 1" boards just to make sure the string line was off the ground.

At some point I'll need to go back through the whole model and check it all, but for now I'm content that it's giving me reasonable figures. Magic number spreadsheet is coming together now...just a few bumps to iron out.

Thanks again, fe1rx for the data!
You are welcome.

Good to see that you are cross checking your assumptions against real world measurements. This is definitely essential!
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