BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read
M2 Technical Topics > Track / Autocross / Dragstrip > M2C Mid-Corner / Corner Exit Issues

Post Reply
 
Thread Tools Search this Thread
      09-28-2020, 08:12 AM   #1
iBrakeLate
Private
71
Rep
77
Posts

Drives: 2020 M2 Competition
Join Date: Dec 2019
Location: Miami

iTrader: (0)

M2C Mid-Corner / Corner Exit Issues

So I finally got the M2 Competition out on track after the mods, and I am having issues with the vehicle mid-corner to corner exit behavior.

The car has the Ohlins R&T with the Ohlins recommended spring rates, Ground Control Camber plates, 265/295 Yokohama A052 tires.

The front has 0 toe, rear has total 1/8th toe in. -3 camber front, -2.1 camber rear (drivers side), -2.7 camber front, -1.7 rear (passenger side). The track I visit most often is mostly all right hand turns, hence the setup being as this. Front rebound is set at 7 clicks, rear at 12 clicks (was originally 7 at rear but softened the rebound after)

The rear of the car starts letting loose from mid corner to corner exit on right hand turns. It is more prevalent on longer sweeping corners.

I am a pretty seasoned driver, and it does the above mentioned over steer with no jerking of the wheel, or rough application of power. In fact if you hold throttle steady and keep the steering angle steady the back ends up coming around.

All nannies are off, so its not a matter of the electronics throwing the car off either.

I was out on track on Wednesday, and back again yesterday (Sunday). On Sunday we took cross temps on tires and the rear can use more camber, front wasn't so bad.

I thought with the amount of stagger running with the tires the car would actually understeer from mid-corner to corner exit, however I can't even apply any power since there is way too much yaw.

I would appreciate anyone who has experience with the F87 chassis to chime in.
Appreciate 0
      09-28-2020, 08:30 AM   #2
Montaver
Captain
Montaver's Avatar
946
Rep
919
Posts

Drives: G20 330i & 981 Cayman GT4
Join Date: Jul 2017
Location: NY

iTrader: (0)

Your alignment doesn't make sense to me, I've never heard of anyone running that way it's not NASCAR. Set both rears to -1.8 with stock toe in. The Ohlins are over sprung and under damped in stock form, the f8x kit is disappointing in my experience. Try softening the rear dampers to add more grip to the rear.
Appreciate 1
Got f1?242.50

      09-28-2020, 09:25 AM   #3
iBrakeLate
Private
71
Rep
77
Posts

Drives: 2020 M2 Competition
Join Date: Dec 2019
Location: Miami

iTrader: (0)

Quote:
Originally Posted by Montaver View Post
Your alignment doesn't make sense to me, I've never heard of anyone running that way it's not NASCAR. Set both rears to -1.8 with stock toe in. The Ohlins are over sprung and under damped in stock form, the f8x kit is disappointing in my experience. Try softening the rear dampers to add more grip to the rear.
Thank you for the input, but I don't think you read anything I wrote, other than the alignment specs.

Actually on a race track where you have 80% of the turns that are right hand turns, and 20% are only left hand turns, the stagger on the camber makes perfect sense. Think about it, the reason why you are using camber is to maximize the contact patch on the corners, and a car has 4 tires. When you turn right, the camber on the right hand of the car actually does not help you with the contact patch, so by compromising a little for the left hand turns, you run less negative camber on one side and your contact patch is increased for 80% of the corners on that given track layout.

Also your recommendation of running less camber in the back again does not make sense, we did cross temps on tires, and the rear is asking for more camber.

I appreciate you trying to help though.
Appreciate 1
CrashFL118.50

      09-28-2020, 10:40 AM   #4
dvas
Lieutenant
dvas's Avatar
376
Rep
488
Posts

Drives: 2017 M2 - Mineral Gray, 6spd
Join Date: Jul 2014
Location: NYC

iTrader: (0)

Do you oversteer on exit in both left and right turns?

I typically like a loose car. But when it gets too wild softening the rear and/or stiffening the front usually does the trick.
__________________
Appreciate 0
      09-28-2020, 11:47 AM   #5
iBrakeLate
Private
71
Rep
77
Posts

Drives: 2020 M2 Competition
Join Date: Dec 2019
Location: Miami

iTrader: (0)

Quote:
Originally Posted by dvas View Post
Do you oversteer on exit in both left and right turns?

I typically like a loose car. But when it gets too wild softening the rear and/or stiffening the front usually does the trick.
The left hand corners on this track aren't really long turns, but the rear is very sensitive to steering input on the right hand turns.
Appreciate 0
      09-28-2020, 11:58 AM   #6
ZM2
Colonel
746
Rep
2,333
Posts

Drives: 2017 LBB M2
Join Date: Mar 2017
Location: Baltimore

iTrader: (0)

The first thing I’d try is equal alignment settings on both sides just to test that change before playing with the dampers. An easy test.

Other than that, it sounds too stiff in the rear.
Appreciate 0
      09-28-2020, 12:01 PM   #7
iBrakeLate
Private
71
Rep
77
Posts

Drives: 2020 M2 Competition
Join Date: Dec 2019
Location: Miami

iTrader: (0)

Quote:
Originally Posted by ZM2 View Post
The first thing I’d try is equal alignment settings on both sides just to test that change before playing with the dampers. An easy test.

Other than that, it sounds too stiff in the rear.
The toe is equal, the camber is not. But the camber will only negatively impact the corner grip if they are equaled out.
Appreciate 0
      09-28-2020, 12:04 PM   #8
ZM2
Colonel
746
Rep
2,333
Posts

Drives: 2017 LBB M2
Join Date: Mar 2017
Location: Baltimore

iTrader: (0)

Quote:
Originally Posted by iBrakeLate View Post
The toe is equal, the camber is not. But the camber will only negatively impact the corner grip if they are equaled out.
I’m following your logic, but alignment is easy to change to see how the car reacts differently before digging into the spring/damper rabbit hole.

I’ve also had a car dialed in that behaved poorly on track (-3F, -2R, 0.04 deg toe in F, 0.28deg toe in rear), and come to find out afterwards the alignment was out of whack. Probably from hitting a pothole or something on the way to the track. Re-aligned and everything was back to normal.

My gut tells me the issue is the rear is too stiff, but double checking and trying diff alignment is easy to do as a test.

Last edited by ZM2; 09-28-2020 at 12:12 PM..
Appreciate 0
      09-28-2020, 04:02 PM   #9
j0oftheworld
Private First Class
j0oftheworld's Avatar
54
Rep
105
Posts

Drives: 01 S2k, 20 M2C
Join Date: Apr 2020
Location: PHX, AZ

iTrader: (0)

How's the usable range in stroke on the rear shocks with the Ohlins? I know they screwed up in designing the coilovers on the rear of the S2000 so if you lowered it an inch you would have only about an inch of shock travel. Most people have settled on a little extra preload in order to achieve ride height and keep it from bottoming out.
Appreciate 0
      09-28-2020, 04:20 PM   #10
iBrakeLate
Private
71
Rep
77
Posts

Drives: 2020 M2 Competition
Join Date: Dec 2019
Location: Miami

iTrader: (0)

Quote:
Originally Posted by j0oftheworld View Post
How's the usable range in stroke on the rear shocks with the Ohlins? I know they screwed up in designing the coilovers on the rear of the S2000 so if you lowered it an inch you would have only about an inch of shock travel. Most people have settled on a little extra preload in order to achieve ride height and keep it from bottoming out.
That is an area which we are going to be looking at actually. Just got off the phone with Brian @ Ohlins, he was super helpful with trying to narrow the problem down.

The way it works on the M2, is you need to set the ride height with the preload adjustment (so the perch on the spring), then match the ride height adjuster (shock length) according to that. This might sound weird, but I am using the terminology from their own manual, which kind of can be mislading, because the ride height adjustment only adjusts the shock/dampener length which by itself will not adjust ride height unless you change the preload.
Appreciate 0
      09-28-2020, 08:24 PM   #11
TUNEDM3
Stay Ripping
31
Rep
499
Posts

Drives: 1M
Join Date: Sep 2008
Location: New York

iTrader: (4)

Sounds like a toe issue in the rear. Possibly recheck your alignment specs.
__________________
THE GOBBLER- S.O.H
Appreciate 0
      09-28-2020, 08:44 PM   #12
M2C AW
First Lieutenant
154
Rep
363
Posts

Drives: 2019 M2C Alpine White
Join Date: Oct 2018
Location: Houston

iTrader: (1)

Quote:
Originally Posted by iBrakeLate View Post
That is an area which we are going to be looking at actually. Just got off the phone with Brian @ Ohlins, he was super helpful with trying to narrow the problem down.

The way it works on the M2, is you need to set the ride height with the preload adjustment (so the perch on the spring), then match the ride height adjuster (shock length) according to that. This might sound weird, but I am using the terminology from their own manual, which kind of can be mislading, because the ride height adjustment only adjusts the shock/dampener length which by itself will not adjust ride height unless you change the preload.
I think you could be looking at your problem. Do the “pinch test” on the rear shocks. Check the clear distance between the lower bump stop and the shock bottom / end by pinching the bellows between your thumb and index finger. In my case, after installing / setting up per Ohlin Instructions, I had a mere half inch of shock travel, before sitting on bump stop. Not good.
Also, I suggest you try 1.8 to 2.0 degree rear camber, irrespective of what your pyrometer is telling you. That’s where most F8x guys end up after some experimentation.
Appreciate 0
      09-28-2020, 10:46 PM   #13
iBrakeLate
Private
71
Rep
77
Posts

Drives: 2020 M2 Competition
Join Date: Dec 2019
Location: Miami

iTrader: (0)

Quote:
Originally Posted by M2C AW View Post
I think you could be looking at your problem. Do the “pinch test” on the rear shocks. Check the clear distance between the lower bump stop and the shock bottom / end by pinching the bellows between your thumb and index finger. In my case, after installing / setting up per Ohlin Instructions, I had a mere half inch of shock travel, before sitting on bump stop. Not good.
Also, I suggest you try 1.8 to 2.0 degree rear camber, irrespective of what your pyrometer is telling you. That’s where most F8x guys end up after some experimentation.
I think we are maybe onto something.

Ever since Wednesday, the day I had it on track, I've actually shortened the shock length by two turns and after reading what you just wrote I went out to check the amount of rod the shock has before the bump stops. Obviously Ohlins USA is closed now to see if under 2 inch of shock travel is sufficient, but this could have been definitely the cause of the erratic behavior of the car.

Just check out the video of the lap and a bit which I posted on Youtube, you'll see how wild the car was.

Appreciate 0
      09-28-2020, 11:38 PM   #14
M2C AW
First Lieutenant
154
Rep
363
Posts

Drives: 2019 M2C Alpine White
Join Date: Oct 2018
Location: Houston

iTrader: (1)

Quote:
Originally Posted by TUNEDM3 View Post
Sounds like a toe issue in the rear. Possibly recheck your alignment specs.
+1
Appreciate 0
      09-29-2020, 03:04 AM   #15
Caduceus
First Lieutenant
Australia
270
Rep
361
Posts

Drives: 2008 135 (sold), 2017 M2
Join Date: Jul 2008
Location: Australia

iTrader: (0)

Quote:
Originally Posted by iBrakeLate View Post

Just check out the video of the lap and a bit which I posted on Youtube, you'll see how wild the car was.

Yikes, you sir, have bigger balls than me. I'd have backed it off a few notches in that light rain. Excellent car control skills though.

I'd be reluctant to make a handling balance assessment in those greasy conditions. However, from what I could see & hear, the rear was breaking traction before it was stepping out which is a throttle application issue, not a suspension problem.

What F&R tyre pressures are you running?
Appreciate 0
      09-29-2020, 08:31 AM   #16
iBrakeLate
Private
71
Rep
77
Posts

Drives: 2020 M2 Competition
Join Date: Dec 2019
Location: Miami

iTrader: (0)

Quote:
Originally Posted by Caduceus View Post
Yikes, you sir, have bigger balls than me. I'd have backed it off a few notches in that light rain. Excellent car control skills though.

I'd be reluctant to make a handling balance assessment in those greasy conditions. However, from what I could see & hear, the rear was breaking traction before it was stepping out which is a throttle application issue, not a suspension problem.

What F&R tyre pressures are you running?
It was 33 front, 32 rear hot.

I was on track for another four hours, and it dried out. The problems I was experiencing that described on my OP is more evident in this short clip. Steering input remains the same, extremely light and smooth throttle application and the rear comes around on exit.

Appreciate 0
      09-29-2020, 09:41 AM   #17
j0oftheworld
Private First Class
j0oftheworld's Avatar
54
Rep
105
Posts

Drives: 01 S2k, 20 M2C
Join Date: Apr 2020
Location: PHX, AZ

iTrader: (0)

I personally don't like the non linear throttle in sport modes. Very touchy with minimal input. Would take some getting used to on the track for sure.
Appreciate 0
      09-29-2020, 05:58 PM   #18
Caduceus
First Lieutenant
Australia
270
Rep
361
Posts

Drives: 2008 135 (sold), 2017 M2
Join Date: Jul 2008
Location: Australia

iTrader: (0)

Quote:
Originally Posted by iBrakeLate View Post
It was 33 front, 32 rear hot.

I was on track for another four hours, and it dried out. The problems I was experiencing that described on my OP is more evident in this short clip. Steering input remains the same, extremely light and smooth throttle application and the rear comes around on exit.

Ok, that video demonstrates it perfectly.
Appreciate 0
      09-30-2020, 08:32 AM   #19
Malakas
Lieutenant
United_States
416
Rep
447
Posts

Drives: 2020 M2c
Join Date: Jun 2011
Location: Houston, TX

iTrader: (0)

Whoa... that must be scary... car looks like its settled and rear just starts to lose grip (lucky it was basically on exit).
Appreciate 0
      09-30-2020, 09:00 AM   #20
M2C AW
First Lieutenant
154
Rep
363
Posts

Drives: 2019 M2C Alpine White
Join Date: Oct 2018
Location: Houston

iTrader: (1)

Quote:
Originally Posted by Caduceus View Post
Ok, that video demonstrates it perfectly.
Looks like rear toe issue. As soon as you go to throttle on corner exit...it steps out
Appreciate 0
      09-30-2020, 11:35 AM   #21
iBrakeLate
Private
71
Rep
77
Posts

Drives: 2020 M2 Competition
Join Date: Dec 2019
Location: Miami

iTrader: (0)

Just an update on this.

We've been talking to Ohlins about the issue with the vehicle dynamics. Did some measurements of the suspension, droop length, rear shock shaft measurements etc... It looks like unfortunately their instruction manual and the setup guide is quiet a bit off. The car doesn't have enough droop, preload is way off too.

As per the setup from the installation manual, the preload is set more than what it is supposed to be which could also be contributing to all of this.

I have a busy week this week, but we are going to make the changes Ohlins has recommended and report back.
Appreciate 0
      09-30-2020, 11:37 AM   #22
iBrakeLate
Private
71
Rep
77
Posts

Drives: 2020 M2 Competition
Join Date: Dec 2019
Location: Miami

iTrader: (0)

Quote:
Originally Posted by Malakas View Post
Whoa... that must be scary... car looks like its settled and rear just starts to lose grip (lucky it was basically on exit).
I assume in the hands of a novice driver, it would definitely be scary. To me it was just more annoying than scary. Losing a lot of drive out of the corners because of this.
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 02:22 AM.




m2
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST