|
|
|
|
|
|
BMW Garage | BMW Meets | Register | Today's Posts | Search |
|
BMW 3-Series (E90 E92) Forum
>
M3 rear guide rods - feedback?
|
|
01-21-2020, 03:13 PM | #23 |
Brigadier General
3058
Rep 3,909
Posts |
But either with or without the brace, the differential is wholly mounted to the rear subframe; 100% of the drive load and torque is routed in the same direction through the subframe. One way the diff can flex a bunch, the other way it can't (as much)...but the force still goes through the subframe.
...what gives? Detailed explanations welcome! |
Appreciate
0
|
01-21-2020, 03:16 PM | #24 | |
Major General
4276
Rep 9,206
Posts |
Quote:
|
|
Appreciate
0
|
01-21-2020, 04:30 PM | #29 |
Brigadier General
3058
Rep 3,909
Posts |
|
Appreciate
0
|
01-21-2020, 04:33 PM | #30 |
Major General
4276
Rep 9,206
Posts |
Are you talking about twisting the body of the half axles themselves? I'm talking about the diff wanting to twist (rotate). If the diff is mounded solid via 4th mount (diff brace or diff lockdown) that will provide lets's assume at least equal torque in opposite direction which will stop the diff rotation. If the diff is moving, wanting to twist (rotate) it will transmit all of these movements to the rest of the vehicle.
|
Appreciate
2
IllSic_Design2124.00 lab_rat394.50 |
01-21-2020, 04:47 PM | #31 |
Major General
4276
Rep 9,206
Posts |
The diff isn't mounted solid. Has only 3 mounts that are also not solid but rubber bushings allowing flex. So is lacking 4th mount, thus wanting to twist. This is an action. Every action has a reaction. So when diff is twisting is loading the tires differently. It will lift one side while push down the opposite. There are different remedies such: different shock setting side to side, different suspension pre-load side to side, or a diff brace.
|
Appreciate
0
|
01-21-2020, 05:47 PM | #34 | |
Brigadier General
3058
Rep 3,909
Posts |
Quote:
You're posting pictures of cars which probably have solid rear axles, which is completely different from the independent rear suspension on our cars. On those cars the diff is rigidly connected to the rear hubs; any movement of the diff is movement of the hub. On ours, there's no rigid connection between them. |
|
Appreciate
0
|
01-21-2020, 06:54 PM | #35 | |
Major General
4276
Rep 9,206
Posts |
Quote:
|
|
Appreciate
1
lab_rat394.50 |
01-21-2020, 07:25 PM | #36 | |
Enlisted Member
44
Rep 47
Posts |
Quote:
|
|
Appreciate
0
|
01-21-2020, 07:56 PM | #37 | |
Major General
4276
Rep 9,206
Posts |
Quote:
|
|
Appreciate
0
|
01-21-2020, 08:06 PM | #38 |
Enlisted Member
44
Rep 47
Posts |
Makes sense. That's why outboarding shocks works. But also why I asked what engine/tranny mounts are used. If diff brace and stock tranny/diff mounts then forces go there and rear end will be more stable but torque will stress engine/tranny mounts and not translate to optimum power to the wheels.
I have a 335xi and have used poweflex subframe bushings, with 335is engine mounts and stock diff bushings. I am sacrificing some power delivery to protect the unibody... a |
Appreciate
0
|
01-21-2020, 09:06 PM | #40 | |
Major General
4276
Rep 9,206
Posts |
Quote:
|
|
Appreciate
0
|
01-22-2020, 01:35 AM | #41 | |
Brigadier General
3058
Rep 3,909
Posts |
Quote:
|
|
Appreciate
0
|
01-22-2020, 03:09 AM | #42 |
Second Lieutenant
87
Rep 236
Posts
Drives: e92 335iA
Join Date: Nov 2018
Location: Prague
|
Most if not all diffs have 3 point mounting pattern because of freedom of movement, vibrations etc. I am sure that Bmw could easily do 4 point pattern if needed/beneficial. That is where I am puzzled with our brace thing, or we could call it poor mans band aid to something else that needs to be addressed...
Anyway when you take a look at these few examples - f.ex. e36 platform I am familiar with, lesser machinery is fine with upper style brace however M3 3,2 (Euro version was much like a racing car, dry sump, 100PS/litre engine, refined little details all over the vehicle incl. this diff)... brace is down, unequal arms, front bolt in a weird (actually in a direction of reaction forces) angle... This all makes me wonder why they went back to that "e30" style mount - 2 bolts up front, one rear silentblock... to save money?
__________________
"If everything seems under control, you're not going fast enough.” Mario Andretti
|
Appreciate
0
|
01-22-2020, 08:07 AM | #43 | |
Major General
4276
Rep 9,206
Posts |
Quote:
|
|
Appreciate
0
|
01-22-2020, 08:24 AM | #44 | |
Major General
4276
Rep 9,206
Posts |
Quote:
https://www.m5board.com/threads/rear...repair.599470/ https://f10.m5post.com/forums/showthread.php?t=1542282 This is not only BMW issue. Plenty of other vehicles experience the same. |
|
Appreciate
0
|
Bookmarks |
|
|