Question for Mechanical Engineers or deep knowledge OG's

Merlin_83 · 01-31-2023, 10:03 AM

Greetings,

I just figured out that by design, the engine in the M3 is supported by the engine mounts, which are part (connected to) the lower sub-assembly. That subassembly essentially 'sits' on the ground, thereby transferring all the weight to the hubs, wheels, etc. - I'm sure this same design concept is used throughout many if not all modern BMWs.

It's pretty neat and ingenious that the frame or chassis per se do not really support all that weight - but in contact with the ground.

Do I have this right?

Cheers,
Merlin

bstone801 · 01-31-2023, 10:29 AM

And how have you arrived to this conclusion?

lagunablue1 · 01-31-2023, 10:45 AM

Every car I've ever worked on has had the engine connected to the subframe via the motor mounts, and control arms connecting the subframe to the hubs.

Transmission still mounts to a crossmember which is bolted directly to the chassis.

(exception being proper body on frame trucks)

pbonsalb · 02-01-2023, 07:16 AM

My 1975 2002 engine bay showing cross member and mounts.

tdott · 02-01-2023, 08:29 AM

The subframe is bolted to the frame.

The weight of the car is supported by the suspension, but that is always the case so i'm not sure what you are getting at?

nrubenstein · 02-01-2023, 08:58 AM

The weight of the car is supported by the springs, specifically. The weight of the engine is absolutely supported by the frame.

Merlin_83 · 02-01-2023, 09:56 AM

Okay I am apparently wrong, but still, it at least appears from a perspective of weight and gravity all the load-bearing forces are from the engine mounts to the sub-frame - and then ultimately hubs, wheels tires, etc.

Guys, it's cool - I was wrong.

Cheers,
Merlin

nrubenstein · 02-01-2023, 11:41 AM

Quote:

Originally Posted by Merlin_83

Okay I am apparently wrong, but still, it at least appears from a perspective of weight and gravity all the load-bearing forces are from the engine mounts to the sub-frame - and then ultimately hubs, wheels tires, etc.

Guys, it's cool - I was wrong.

Cheers,
Merlin

Effectively all weight travels through the spring. It's really simple.

Longboarder · 02-01-2023, 12:02 PM

Quote:

Originally Posted by nrubenstein

Effectively all weight travels through the spring. It's really simple.

Curious how is this affected by airbags?

Maybe the same way I suppose.

01-31-2023, 10:03 AM	#1
Merlin_83 Merlin 474 Rep 730 Posts Drives: 2012 BMW M3 6MT w/ZCP Join Date: Feb 2014 Location: United States iTrader: (0) Garage List 2012 BMW M3 ZCP [0.00] 2008 BMW 335i [0.00] 2008 BMW 335xi [0.00]	Question for Mechanical Engineers or deep knowledge OG's Greetings, I just figured out that by design, the engine in the M3 is supported by the engine mounts, which are part (connected to) the lower sub-assembly. That subassembly essentially 'sits' on the ground, thereby transferring all the weight to the hubs, wheels, etc. - I'm sure this same design concept is used throughout many if not all modern BMWs. It's pretty neat and ingenious that the frame or chassis per se do not really support all that weight - but in contact with the ground. Do I have this right? Cheers, Merlin __________________ 2012 E92 M3 ZCP \| 2008 E90 335xi \| 2008 E90 335i \|
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01-31-2023, 10:29 AM	#2
bstone801 Private First Class 94 Rep 198 Posts Drives: Alpine e90 M3 slick stick Join Date: May 2015 Location: Boise, ID iTrader: (0)	And how have you arrived to this conclusion?
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01-31-2023, 10:45 AM	#3
lagunablue1 Second Lieutenant 348 Rep 207 Posts Drives: E90 M3 / F97 X3M Join Date: Jun 2020 Location: ON iTrader: (1)	Every car I've ever worked on has had the engine connected to the subframe via the motor mounts, and control arms connecting the subframe to the hubs. Transmission still mounts to a crossmember which is bolted directly to the chassis. (exception being proper body on frame trucks) __________________ -2007 Z4M - Interlagos Blue -2008 E90 M3 - Interlagos Blue, 6MT, slicktop -2020 X3MC - Phytonic Blue Last edited by lagunablue1; 01-31-2023 at 10:56 AM..
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02-01-2023, 07:16 AM	#4
pbonsalb Lieutenant General 5231 Rep 10,614 Posts Drives: 18 F90 M5, 99 E36 M3 Turbo Join Date: Feb 2011 Location: New England iTrader: (4)	My 1975 2002 engine bay showing cross member and mounts. Attached Images
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02-01-2023, 08:29 AM	#5
tdott Brigadier General 3941 Rep 3,986 Posts Drives: M3 Join Date: Nov 2010 Location: South FL / 6ix iTrader: (4)	The subframe is bolted to the frame. The weight of the car is supported by the suspension, but that is always the case so i'm not sure what you are getting at? __________________ N/A S65 Headers Before/After Dyno Results
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02-01-2023, 08:58 AM	#6
nrubenstein Captain 567 Rep 801 Posts Drives: E30 M3/E36 M3/E46 M3/E90 M3 Join Date: Dec 2016 Location: Washington, DC iTrader: (2)	The weight of the car is supported by the springs, specifically. The weight of the engine is absolutely supported by the frame. __________________ 2011.75 E90 M3 \| 2006 GMC Sierra LBZ \| 2004 X5 3.0i 6MT \| 1995 M3 S50B32 \| 1990 325is \| 1989 M3 S54B32 Hers: 1996 911 Turbo \| 1989 325iX
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02-01-2023, 09:56 AM	#7
Merlin_83 Merlin 474 Rep 730 Posts Drives: 2012 BMW M3 6MT w/ZCP Join Date: Feb 2014 Location: United States iTrader: (0) Garage List 2012 BMW M3 ZCP [0.00] 2008 BMW 335i [0.00] 2008 BMW 335xi [0.00]	Okay I am apparently wrong, but still, it at least appears from a perspective of weight and gravity all the load-bearing forces are from the engine mounts to the sub-frame - and then ultimately hubs, wheels tires, etc. Guys, it's cool - I was wrong. Cheers, Merlin __________________ 2012 E92 M3 ZCP \| 2008 E90 335xi \| 2008 E90 335i \|
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