[Daytona_550]

Originally Posted by bentom2

I run the same brake setup and have used 1.11 in the past.I also drive both with and without stability control depending how I’m feeling, conditions, and familiarity with the track.

The tail wag went away after I changed out the front torque arm bushings, rear toe links, and installed coilovers. I did them all at once, so couldn’t tell you which actually was the cause, but the car has been stable under hard braking since.

Good info, thanks!

[okla_m2c]

Reviving this thread here.. so I've been tracking the M2C for ~2ish years now, and the entire time I thought the 'wagging' was normal. It wasn't until this past weekend when an instructor pointed this out to me, asking whether or not if I had a bad habit with my hands or if it was the car. I told him that it wasn't intentional, and believed it was the car.

After speaking to a few folks at the track with the same car, they asked what steering setting I was driving in, and told them I was in Comfort. They recommended changing it to Sport+, and after a few sessions, I noticed that it was notably less 'waggier' in the hard braking (threshold) zones. The wags wasn't completely gone, but was significantly less.

For what it's worth, I was running in MDM mode, M Perf Coilovers, and ~2.5 degrees of camber.

[medphysdave]

I found that the front tension arm bushing replacement got rid of the squirm under heavy braking and the rear toe links got rid of the squirm under acceleration. I track in sport steering setting. MDM on. Next time out I plan to turn all the nannies off.

[ThreeStripes]

It’s traction and dsc related. Does it way more with dsc on in Sport and shit traction than it does on stickers in Sport+.

*edit* reconfirmed this again today on track. Now that I have the wagging or yaw or “pulling” under threshold braking sorted I can move on to the brake coding to get a more consistent pedal and avoid the weird abs issue I see occasion braking hard over curbing.

[BackOnBlack]

Does the M2C have mechanical rear diff or an e-diff?

[ThreeStripes]

Originally Posted by BackOnBlack

Does the M2C have mechanical rear diff or an e-diff?

You can read all about the M active differential here: https://f80.bimmerpost.com/forums/sh....php?t=1018024

[E90convert]

Originally Posted by ThreeStripes

It’s traction and dsc related. Does it way more with dsc on in Sport and shit traction than it does on stickers in Sport+.

*edit* reconfirmed this again today on track. Now that I have the wagging or yaw or “pulling” under threshold braking sorted I can move on to the brake coding to get a more consistent pedal and avoid the weird abs issue I see occasion braking hard over curbing.

I also noticed this at Mid-Ohio braking on the back straight. Sport+ I would get wagging. DSC off, no more wagging.

[BackOnBlack]

Originally Posted by E90convert

I also noticed this at Mid-Ohio braking on the back straight. Sport+ I would get wagging. DSC off, no more wagging.

I had similar experience at Summit Point recently with the G80. When I had DSC or MDM on, I had the wagging. On a dry session, while being faster, I had DSC off and wagging was either minimal or non-existent. This is the reason I am wondering if the stability systems and logic include some changes/adjustments to the e-diff operations.

[ThreeStripes]

Originally Posted by BackOnBlack

I had similar experience at Summit Point recently with the G80. When I had DSC or MDM on, I had the wagging. On a dry session, while being faster, I had DSC off and wagging was either minimal or non-existent. This is the reason I am wondering if the stability systems and logic include some changes/adjustments to the e-diff operations.

What tire?

[///MPhatic]

Originally Posted by E90convert

I also noticed this at Mid-Ohio braking on the back straight. Sport+ I would get wagging. DSC off, no more wagging.

My guess is that I've never experienced this because all I ever drive in is everything off. Although it's interesting to me how/why the car is creating this instability. I'm sure there's a reason for it, maybe something that's only detectable at low speeds.

[ThreeStripes]

Originally Posted by ///MPhatic

My guess is that I've never experienced this because all I ever drive in is everything off. Although it's interesting to me how/why the car is creating this instability. I'm sure there's a reason for it, maybe something that's only detectable at low speeds.

It’s only encountered under track conditions at an intermediate pace or above. It’s not something you’d ever experience on the street unless you’re driving like a complete dickhead on public roads

[medphysdave]

Originally Posted by ThreeStripes

It’s only encountered under track conditions at an intermediate pace or above. It’s not something you’d ever experience on the street unless you’re driving like a complete dickhead on public roads

There's some truth to this. I noticed the squirm mostly when accelerating hard out of a corner. Or low speed and really jumping on the throttle. The squirm under hard braking was only noticed on track or on the street when bedding the track pads. You don't really notice it unless pushing the car very aggressively.

[BackOnBlack]

Originally Posted by ThreeStripes

What tire?

PS4S

Originally Posted by ThreeStripes

It’s only encountered under track conditions at an intermediate pace or above. It’s not something you’d ever experience on the street unless you’re driving like a complete dickhead on public roads

Originally Posted by medphysdave

There's some truth to this. I noticed the squirm mostly when accelerating hard out of a corner. Or low speed and really jumping on the throttle. The squirm under hard braking was only noticed on track or on the street when bedding the track pads. You don't really notice it unless pushing the car very aggressively.

For me, it happens when braking from over 120mph+ with DSC or MDM on. Under acceleration all is well, actually great!

[M2guru]

I get wagging under braking on the track with DSC off. Typically it's when braking hard in a straight line from over 100mph. This is with street tires (200tw). Multiple factors are likely included such as: track condition, tire temp, alignment (likely rear toe), etc... It has not been too concerning to me, but it would be better if it wasn't there.