Squirrelly-Loose feeling in rear end

spitfun · Post by **spitfun** » Sun Feb 05, 2023 5:01 am

I have finished the front suspension on my car along with an MHD stage 1+ tune. Car runs great and the front seems good but I am noticing a loose feeling in the rear on acceleration and I am not breaking traction,it just seems to sway back and forth. What do I need to upgrade in the rear to get rid of that??

Marcoose · Post by **Marcoose** » Sun Feb 05, 2023 5:23 am

Like il Commendatore said, every car understeers and oversteers, it depends how you drive it. He also said convertibles are for playboys. He was quite the icon.

IMHO, this is still a new car to you and you need to find its sweet spot. You just need more seat time. (That’s my saying.)

Besides, suspension works with everything else; tyres, alignment, balancing, brakes, pedal control, driving style, road condition, etc. And you’ve just made the front stiffer. That’s bound to affect the rear. It can be a number of things. On the internets, you’ll get 36,000 opinions, most wrong, starting with mine.

Chippie · Post by **Chippie** » Sun Feb 05, 2023 10:06 am

Are the roads damp? What tyres do you have on the rear?
It sounds like the traction control is trying to keep the rear wheels under control and struggling with the extra power of your remap

B21 · Post by **B21** » Sun Feb 05, 2023 10:28 am

At least two possible issues…

They all do that sir…trying to put 400 ish BHP through two tyres can result in a yaw from the two rear wheels as they struggle to feed the power down with the DSC system implementing its faux LSD strategy…

Another option is if the RTAB bushes are worn then you get toe out effects under load which will give a rear wheel steering effect with a pronounced fish tailing effect.

General wear n tear is another issue plus of course wheel alignment..have you had that checked?

spitfun · Post by **spitfun** » Sun Feb 05, 2023 12:11 pm

I should mention the car has 110k miles on it. I am going to check the rear bushes today. I am feeling this at partial throttle too,just more pronounced the more you push it. I do not believe it is a break in traction-I am not pushing it that hard when it happens, it just doesn't feel as stable back there-it has been mentioned here quite often. What do you guys think of this,would it be beneficial in your opinion?

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B21 · Post by **B21** » Sun Feb 05, 2023 12:30 pm

I’d go for an uprated / new set of bushes all round on the rear …

Then a geometry check

The incorrect ARB won’t help..

Once you’ve done ALL those things maybe look at chassis stiffening…

The E89’s chassis stiffness is not its greatest vulnerability…

enuff_zed · Post by **enuff_zed** » Sun Feb 05, 2023 1:02 pm

Marcoose wrote: ↑Sun Feb 05, 2023 5:23 am .... you’ve just made the front stiffer. That’s bound to affect the rear. ....

I was about to say exactly the same thing.
Even if you replaced the front with OEM stuff it is going to be much more efficient than the old stuff on the rear.
I think I'd be looking to do the rear to match the front and see what happens then.

spitfun · Post by **spitfun** » Sun Feb 05, 2023 1:05 pm

I think the lower wishbone bushing at the wheel is shot (I can move it with very little effort) ,the one at the diff seems to be fine (no movement) also the one at the trailing arm front will be replaced as I already bought the uprated full rubber,stiffer one for it along with the spacers.

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B21 · Post by **B21** » Sun Feb 05, 2023 1:22 pm

I see you have one of the two bushes 2,3 for the ball joints but what you almost certainly need is 4..

Obviously 6 and 14 may be worn..but its 4 then 2,3 that are the priority.

You may find 18 doesn't give youe nough adjustment on toe in FWIW

Assume ride height is stock tehn camber should be able to be brought in...

FWIW even new those adaptive dampers were not the greatest..

spitfun · Post by **spitfun** » Sun Feb 05, 2023 2:58 pm

I have ordered 3,4 and 6. I am at stock ride height so I do not believe I need to change 18... I know the stock adaptive shocks are not the best,but I don't think that is making the rear end seem like it is steering left and right under acceleration .

B21 · Post by **B21** » Sun Feb 05, 2023 6:41 pm

spitfun wrote: ↑Sun Feb 05, 2023 2:58 pm I have ordered 3,4 and 6. I am at stock ride height so I do not believe I need to change 18... I know the stock adaptive shocks are not the best,but I don't think that is making the rear end seem like it is steering left and right under acceleration .

Normal hallmark of RTAB tired resulting in toe out..lots of write ups on various BMW forums ...shops on the matter..

FWIW I've gone with adjustable toe plates

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and these babies to special order..

https://www.hardrace.com/Product_detail ... &MainType=

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