Unstable rear end while shifting and turning solution

[M3MATT]

I figured this might be helpful for a few people a few years down the line, so I lights as well put it out there!

I usually drive my car with mdm on and in DCT setting 5. And if I shift around redline while turning, the rear end seamed to wiggle and become unstable.

The simple solution is go to DCT setting 4! Shifts are still just as quick, but just less violent, it almost feels like it slips the clutch a bit to make the car become less unsettled.

This made a great difference on track and on backroads for me!

[omgzirra_exe]

no. the solution is to get solid rear subframe bushings.

[Redd]

Yeah you haven't really driven an E9x M3 until you've driven one with solid rear subframe bushings.

[CamasM3e93]

Originally Posted by Redd

Yeah you haven't really driven an E9x M3 until you've driven one with solid rear subframe bushings.

Tell us more! Just did coil overs and a set of GAS monoball front control arms with plans for diff and diff / rear subframe mounts as my next step, probably next spring. What specific benefits and drawbacks do you experience with solid subframe bushings?

[Redd]

A lot more chassis rigidity. You can actually feel the springs and dampers working. The chassis just feels tighter and newer. Greatly improved rear end stability. The rear end shimmy over bumps, bridge joints is gone. Rear end just feels more stable and predictable and gives you more confidence overall.

Drawbacks - none. No additional NVH. Aside from cost there is no reason not to do this mod. The E9x GTS came with solid rear subframe as did the F10 M5 and F8x M3/4. Imho the E9x M3 should have come from factory with solid rear subframe.

[MineralWhiteF80]

The benefit of solid subframe bushings and essentially "WOT powershifting" in a turn are two completely different things. If you are in a fast DCT shift setting and you are full throttle around a fast corner and shift mid-corner, the car is going to try to chirp the tires due to the violent shift speed, which makes the car unstable and want to step out. Having solid subframe bushings does not cure this mid-corner shift instability but it does help the heavy braking stability.

Separate example: My F82 DCT with solid rear everything gets crazy loose on a race track when when I shift mid corner in the fastest shift setting. Sometimes it chirps the tires shifting into 4th gear on the street in S3 shift speed. I only ever drive the car on a race track in the middle S2 shift setting because of how rowdy the shifts are in mid-corner.

[omgzirra_exe]

Originally Posted by MineralWhiteF80

The benefit of solid subframe bushings and essentially "WOT powershifting" in a turn are two completely different things. If you are in a fast DCT shift setting and you are full throttle around a fast corner and shift mid-corner, the car is going to try to chirp the tires due to the violent shift speed, which makes the car unstable and want to step out. Having solid subframe bushings does not cure this mid-corner shift instability but it does help the heavy braking stability.

Separate example: My F82 DCT with solid rear everything gets crazy loose on a race track when when I shift mid corner in the fastest shift setting. Sometimes it chirps the tires shifting into 4th gear on the street in S3 shift speed. I only ever drive the car on a race track in the middle S2 shift setting because of how rowdy the shifts are in mid-corner.

Gears 1, 2, and 3 are very aggressive, while gears 4 through 7 are rather smooth in my experience. I don't use that garbage GTS tune either; I just use your standard Euro ZB flash.

Although I do not disagree with you, as I do use S3 in the rain religiously, I don't use anything higher. This is more to do with keeping the car stable out of corners when I am in a full WOT upshift.

The rear end tends to move around too much with the standard rubber bushings, affecting everything connected to it. Upgrading to solid rear subframe bushings and upgraded diff bushings should minimize drivetrain slop and stabilize the subframe, which would make the rear end more stable in every scenario. So technically it's the combination of the subframe bushings and the diff bushings... since the diff bushing is foam... lol.

Even in my S2000, I had to buy rigid collars to basically lock the subframe in place and prevent it from shifting around so much because from the factory, it had a solid 2mm gap around the bolts, which created too much instability on the track.

[Shrike360]

Originally Posted by CamasM3e93

Tell us more! Just did coil overs and a set of GAS monoball front control arms with plans for diff and diff / rear subframe mounts as my next step, probably next spring. What specific benefits and drawbacks do you experience with solid subframe bushings?

FYI, my car is literally in the shop right now with the rear subframe dropped for solid bushings, hotchkis sway bar and fresh OEM diff bushings. Also, completely refreshed every arm up front, along with monoballs and sway bar. May have to figure out a PDX area meetup at some point.

Planning to do MCS coilovers next year. Didn't feel like dropping $12k on the car in one year 😬

[M3MATT]

Originally Posted by CamasM3e93

Tell us more! Just did coil overs and a set of GAS monoball front control arms with plans for diff and diff / rear subframe mounts as my next step, probably next spring. What specific benefits and drawbacks do you experience with solid subframe bushings?

What Redd said. So worth it!

I sell CMP arms/bushings on my site. His raise the subframe up 8mm for roll center and bump steer correction. Pretty kick ass imo!

[M3MATT]

Originally Posted by omgzirra_exe

no. the solution is to get solid rear subframe bushings.

Haha. Cars had them in for a while- the solid bushings irritated the issue slightly. The subframe use to soak up some of that “kick” but with solid it just goes right to the wheels.

My car has solid bushings in every position, along with adjustable arms in ever position. it’s a ring tool but with an interior.

[PACarGuy]

Originally Posted by Redd

Yeah you haven't really driven an E9x M3 until you've driven one with solid rear subframe bushings.

Just got some installed on mine. Feels so much better...

[omgzirra_exe]

Originally Posted by M3MATT

Haha. Cars had them in for a while- the solid bushings irritated the issue slightly. The subframe use to soak up some of that “kick” but with solid it just goes right to the wheels.

My car has solid bushings in every position, along with adjustable arms in ever position. it’s a ring tool but with an interior.

that wild lol

im in the same boat as you. everything is done minus interior.

[M3MATT]

Originally Posted by PACarGuy

Just got some installed on mine. Feels so much better...

Such a worth it mod. Front thrust arm bushing, adjustable rear toe arm, and rear lower inner control arm bushing are great too. I sell them on my store 🤘

[TboneS54]

Originally Posted by M3MATT

What Redd said. So worth it!

I sell CMP arms/bushings on my site. His raise the subframe up 8mm for roll center and bump steer correction. Pretty kick ass imo!

That's for E46 where you epoxy/weld in plates that are about 1/8" thick. It corrects for the additional thickness.

Doesn't make sense to raise the subframe on e9x/e8x chassis.

[M3MATT]

Originally Posted by TboneS54

That's for E46 where you epoxy/weld in plates that are about 1/8" thick. It corrects for the additional thickness.

Doesn't make sense to raise the subframe on e9x/e8x chassis.

On lowered bars or cars they spend time higher up in travel (compressed springs) yes, it does. It returns back to OEM geometry on lowered cars, and makes “ideal” geo last longer on the stroke…

It does the same thing with the diff too. It corrects your axle angle. It all works great!

You can take a look on my site for more info on how it works. Schirmer cars use roll center and bump steer correction in subframes too. It’s fast!

Heres a link!

[TboneS54]

Ah how could I forget the slammed cars with ruined suspension geometry.

[M3MATT]

Not even slammed. Stock cars that go through travel often can still benefit from it. But slightly lowered cars (track spec rideheight) have the best benefit

[darren p.]

Originally Posted by M3MATT

Schirmer cars use roll center and bump steer correction in subframes too.

meaning their solid subframe bushings are similar to yours in height to correct roll center and bump steer? Curious as I have a set of Shirmer bushings I have yet to install.

[omgzirra_exe]

Originally Posted by darren p.

meaning their solid subframe bushings are similar to yours in height to correct roll center and bump steer? Curious as I have a set of Shirmer bushings I have yet to install.

a true Schirmer spec e9x uses a rear diff lift where they raise the diff completely to bring the whole driveline to neutral.

[M3MATT]

Originally Posted by darren p.

meaning their solid subframe bushings are similar to yours in height to correct roll center and bump steer? Curious as I have a set of Shirmer bushings I have yet to install.

Yes, but I’m not sure what the number/geo effect is. They also have excentric bolts that you can also buy.

I have a buddy with a Schimer car and he said it’s nothing too out of the ordinary- one car has a bladed sway bar. Rest are normal.

They just have CRAZY setups and even crazier drivers

[M3MATT]

Originally Posted by omgzirra_exe

a true Schirmer spec e9x uses a rear diff lift where they raise the diff completely to bring the whole driveline to neutral.

Thats what CMP’s diff lift kit does. It raised both thr Subframe and diff up +8mm. It’s a really unique piece of kit. I love mine!

It keeps everything in line! While turning/compressing, or when dropped. So his bushings even have benefit on stock cars.

Theres a reason I sell his stuff! He’s the only one doing it

[amrazM]

Originally Posted by omgzirra_exe

a true Schirmer spec e9x uses a rear diff lift where they raise the diff completely to bring the whole driveline to neutral.

I considered doing this but for my street car it just seemed like too much, I raised the car as much as my clubsports would go.