Calming down the rear on a Z4Mc

[StealYourFace2]

Hey folks,

I got stockish (oem plus) 07z4 coupe last year, crazy clean 39k mile (
I’m
Up to 52000 miles now with the car put up for the winter) - so I like it


First Hpde at the glen was open solo so I got a lot of time with the car…. Rear was twitchy as hell ( I’m used to 330s and e36 m3, less power and longer wheelbase) … on Kuhmo 730 staggered.


The long hood and sitting so far back feels like a c5 or 6 vette which brings me to my tank slapping oversteer. ( a different alignment helped -3.0 0 toe front, -2.0 and a total 1/10 toe in rear).

c6 z06 guys put smaller rear bars on to calm things down… I feel like 22 mm bar in the back of this short wheelbase 330 hp car is a bit much… I have to think any e46 rear bar will work ( I’m also sure there’s a dozen different ones from Europe 318i to drop tops to wagons Ect)


Advise?

Thanks!

[Michael9218]

Shouldn’t be twitchy and over steering. Mine is every bit as neutral and planted as my old E36 M3 racecar.

Is the suspension all stock? Check the condition of the bushings, particularly the rtab.

[belcom]

bit more camber like 2.2-2.5 and 1/16 total toe rear, sticky tires, good suspension setup configured on the softer side and rear likes to be low on this chassis (not inside the fender low, but maybe like a finger or a bit higher). Front is ok, if you are not under steering but could always use more camber, zero toe is good.

But the thing is, E86 is twitchy. Short wheel base, quick steering etc. I've driven e46 m3, e92 m3 and those cars feel like fast race boats in comparison. Gotta learn to drive the Z4M smoothly to keep it under control.

Also, program the M mode for traction control. Its kinda in between on and completely off. It is way less intrusive than full traction control but will still catch you if things get real. Its pretty awesome actually and allows you to get more confident pushing the car. Eventually once you get everything sorted and with some R compound tires you probably will turn off traction control completely.

[vt100]

How old are the tires?

[StealYourFace2]

^new

[Vanne]

if you think the issue is with a too tights rear bar, disconnect it and see how you go. If your running original shocks and springs after all this time, id start there instead of the rear sway.

[3002 tii]

Originally Posted by StealYourFace2

Hey folks,
First Hpde at the glen was open solo so I got a lot of time with the car…. Rear was twitchy as hell ( I’m used to 330s and e36 m3, less power and longer wheelbase) … on Kuhmo 730 staggered.

The long hood and sitting so far back feels like a c5 or 6 vette which brings me to my tank slapping oversteer. ( a different alignment helped -3.0 0 toe front, -2.0 and a total 1/10 toe in rear).

c6 z06 guys put smaller rear bars on to calm things down… I feel like 22 mm bar in the back of this short wheelbase 330 hp car is a bit much… I have to think any e46 rear bar will work ( I’m also sure there’s a dozen different ones from Europe 318i to drop tops to wagons Ect)

Welcome back bud. I used to frequent the E90 N52 section back when I had my 3.0si coupe.

As for rear end being squirrely, I'll echo Michael9218 suggestion on RTAB. I recently swapped out mine for a pair of SDW monoball RTABs and it made a huge difference. But keep in mind the second you start updating 1 component back there, other "issues" may surface given 1) age of car and 2) mix of oe and non-oe parts. Do you happen to have any videos? That would be helpful in understanding what you're experiencing and under what circumstances.

As for sitting far back, that takes some getting used to but eventually your ass will develop a spidey sense for when the rear end kicks. And the M's hydraulic steering makes correction way easier than the EPS on other models. But overall, I'd say the Z4 M is way harder (but more rewarding) to drive than an E46 M3. Those cars better balanced and easier to drive at the limit imo.

I was at the Glen back in July w/ Metro PCA. Not sure if i'll make it up again before season end but we should try to coordinate events, perhaps NJMP in Oct. =)

[dre99gsx]

Go for the 3.0si rear sway, it's 18mm and is what I run. No rear sway will hurt you in other areas of that track (but you can try it as well).

I ran the Glenn a few times and the rear felt alive, but not twitchy. Your coilover damper settings (Rebound/compression) may have manage that effect to give you more time to feel the back end coming around.

[StealYourFace2]

^^ are there any fitment issues with the si bar?

[amcp]

Previous owner installed Turner Front/Rear sways on my M coupe and I had the same issue with rear end twitchiness. Reverting to the OEM rear sway is 100% the way to go.