M3 corner/high speed stability issues

[ChuMpion3]

Add me to the list. The car felt like a video game understeer. It wasn’t unstable (no wheel noise) but also wasn’t going where I was pointing it. Conditions were dry.

[Brasko]

Originally Posted by silverstar335

Get the GTS differential coded and a set of rear toe links, problem should go away.

Exactly what I was thinking.

[paliknight]

Taken ramps at upto 85MPH in my 18 M3 base and 18 M3 ZCP no issue. DSC on.

[mechanic75]

Originally Posted by paliknight

Taken ramps at upto 85MPH in my 18 M3 base and 18 M3 ZCP no issue. DSC on.

Mine was at low speeds not high.

[paliknight]

Originally Posted by mechanic75

Mine was at low speeds not high.

I know that's why I put up to. I tried it at multiple times at different speeds. Just trying to give another datapoint if it helps.

[termigni]

Originally Posted by neilum

What tires on it? and what condition?

My old S2000 used to do that mid-corner. If you lifted the entire rear of the car would become suddenly unsrpung and felt very unnerving. However, I have not noticed this behavior in the F80, there is no mid-corner weight transfer, that I can feel at least.

Car is actually very planted.

Sounds like something is off, I was doing 140 at the track and the car was solid.

Are all of the bolts connected to the front or rear sway maybe? Was the car ever modified?

How did you solve that issue on your old S2000? I have that issue with my S2 and I think it's mainly due to the wrong tire size in the front and/or the tire brand. was it something else for you? It scares the crap of me when I track this car. The tires are too new to consider replacing already...

[Nikolas]

I didn't notice this on my ED this month. I cruised at 125 mph on the autobahn (A7) for some pretty long stretches and the car felt very planted. The wife didn't even complain. I also took it up the Grossglockner and it really did well - even in some sketchy passing zones where the road was so narrow I had literally inches between the bus I was passing and a rock wall - pucker moment (wife did complain here).

Mines a competition package 6 speed if that makes any difference?

[TanzaniteBlue]

Appologies for bumping an old thread, but I have a 2018 F80 ZCP, with 666Ms with PSS, full GTS software and CS EDC and it still occurs. This is an issue on all of their software. Even in the winter when I first got my car it did this on the factory winter set. My 2015 M4 that I used to have would rock back and forth between under and oversteer on the OEM winter set. MDM gets rid of it entirely. GTS software does not solve this. I haven't touched my factory alignment, my steering wheel is perfectly straight and the car does not drift. I will say that the GTS MDM/DSC has dramatically reduced DSC cutting in during the 2-3 and 3-4 gear change on full throttle.

[viva_brasil]

Try turning traction control off entirely? I could tell in MDM mode the diff and / or rear brakes are being actuated in a way that makes the car either want to tighten the steering radius or widen it. I don't fight it, just maintain throttle + steering input and it usually helps get better drive through and out of the corner. This is only on the street, at the track I turn everything off and I don't notice it trying to intervene as much (by intervene I mean with the dynamics of the car, not cutting power).

I find it interesting in MDM mode, though I think they still haven't figured out how to make it smooth and consistent. The rear wheel steer is a much easier way to get the intended effect in a simpler more consistent manner.

[TanzaniteBlue]

After driving some more on GTS software, it still occurs. If you take a freeway off ramp at normal speed and hold the throttle or never get on it, it does not occur. If you release the throttle it almost always immediately triggers the weird behavior. Does not occur in MDM from what I can tell, and it does not occur on twisty roads.

[Kimeran]

What tyres are you all running with?

So my friend has a 2014 M4, only thing done was H&R springs and spacers.
His car was always perfectly fine. Recently he changed rear tyres and put Michelin PSS 285/35/19 (still has the 255/35/19 at the front), his car now behaves exactly like what all of you are talking about.
We swapped wheels and he put my 666M wheels on his car and it's perfectly normal again, no traction cutting in etc.

[nicknaz]

Originally Posted by TanzaniteBlue

After driving some more on GTS software, it still occurs. If you take a freeway off ramp at normal speed and hold the throttle or never get on it, it does not occur. If you release the throttle it almost always immediately triggers the weird behavior. Does not occur in MDM from what I can tell, and it does not occur on twisty roads.

Maybe it's the car telling you not to lift so much and so abruptly mid corner

[ROBERT1183]

I just felt this on my 2018 competition 6mt today. Coming off an exit ramp doing about 35-40 I let off the throttle and the rear got squirrelly. Never felt like that before. Have taken a few turns at much higher speeds and couldn't believe how well it handled. Car has 1200 Miles on it. It was 90 degrees out and I was driving for 45 min on the highway before exiting so it's definitely not cold tires.

[minn19]

Originally Posted by nicknaz

Maybe it's the car telling you not to lift so much and so abruptly mid corner

^This, you are just asking for problems. As an old motocrosser I learned this the hard way a couple of times. Never chop the throttle if you can help it.

Originally Posted by ROBERT1183

I just felt this on my 2018 competition 6mt today. Coming off an exit ramp doing about 35-40 I let off the throttle and the rear got squirrelly. Never felt like that before. Have taken a few turns at much higher speeds and couldn't believe how well it handled. Car has 1200 Miles on it. It was 90 degrees out and I was driving for 45 min on the highway before exiting so it's definitely not cold tires.

I’ve only had mine for 1400 miles and thankfully I’ve not come across anything close to this behavior. Either with full nannies or in MDM. I hope you guys find an easy solution.

[nicknaz]

Originally Posted by minn19

I hope you guys find an easy solution.

Changing the driver inputs is a free mod.... e.g. don't lift

Could also check out the rear alignment, particularly the toe (my '15 came from the factory almost 0 rear toe, and i liked it better when i added rear toe in)

[SenorFunkyPants]

Originally Posted by nicknaz

Could also check out the rear alignment, particularly the toe (my '15 came from the factory almost 0 rear toe, and i liked it better when i added rear toe in)

I had an alignment check a couple of months ago on my 2017 CP and that made quite a difference as the rear toe on one tyre was out...an alignment would be my first check, a disparity between rear wheels can make the car drive really quite strangely.
The spec is 7 minutes toe in each rear wheel for a total of 14 mins...plus/minus 6 mins.
After the alignment and now that the MPS4S I have on the rear have worn in, the car handles exceptionally well....gone is the feeling that the car wanted to chuck you off the road the first chance it got.

[mechanic75]

Originally Posted by nicknaz

Changing the driver inputs is a free mod.... e.g. don't lift

Could also check out the rear alignment, particularly the toe (my '15 came from the factory almost 0 rear toe, and i liked it better when i added rear toe in)

Its not a driver input issue. When you get it you will know what we are talking about. Its a quirk.

I have a M3CS now and it has not done it once.

I drove my old CP briefly last week and I got it. CP was corner balanced, professionally geo'd and on PS4S. I have also had it on hot Cup 2's.

[nbennettksu]

2015 F80, M adaptive here... I've cornered long swooping highway exits in the 80's with no unsettling issues...

[minn19]

Originally Posted by mechanic75

Its not a driver input issue. When you get it you will know what we are talking about. Its a quirk.

I have a M3CS now and it has not done it once.

I drove my old CP briefly last week and I got it. CP was corner balanced, professionally geo'd and on PS4S. I have also had it on hot Cup 2's.

I don't want to speak for him, but I don't think he was saying it was the fix to the entire issue. It definitely looks like a legitimate issue and it sucks when you have a weird one like that.

Congrats on the CS by the way!

[FC]

TLDR, but I have a mid-June 2018 ZCP and see no such issues. Tracks dead straight, massive amounts of grip, full control and predictability in all situations. Drove it 1400+ miles in Europe and and a 100+ in the US.

...must be my moonroof spec.

[TRZ06]

Originally Posted by ROBERT1183

I just felt this on my 2018 competition 6mt today. Coming off an exit ramp doing about 35-40 I let off the throttle and the rear got squirrelly. Never felt like that before. Have taken a few turns at much higher speeds and couldn't believe how well it handled. Car has 1200 Miles on it. It was 90 degrees out and I was driving for 45 min on the highway before exiting so it's definitely not cold tires.

It is the poor rebound damping.

All, and I mean ALL of the rear-end instability, whether from lifting throttle, braking, or hitting a dip in the road, left my car the day I trashed the shitty stock shocks for Ohlin R/T coilovers.

[minn19]

Originally Posted by TRZ06

It is the poor rebound damping.

All, and I mean ALL of the rear-end instability, whether from lifting throttle, braking, or hitting a dip in the road, left my car the day I trashed the shitty stock shocks for Ohlin R/T coilovers.

I came around and ended up mostly agreeing with you about the early non comp pack cars suspension tuning. But, the ZCP (at least 18s and I'm guessing earlier ones as well) don't have the same tuning issue. It would be happening on all of the cars and that doesn't appear to be the case, it certainly isn't with mine. It seems to be something else and not the basic setup of the suspension.