[Ratkiller]

I flushed the brake fluid twice now (Motul RBF 660) and I'm still experiencing a random mushy pedal under heavy braking when at the track. I'm thinking there may still be an air bubble somewhere in the system, possible the ABS. I recall some cars needing they ABS activated/opened to properly flush the system. Is this the case with the M2C?

[doughboy]

If its random or variable, I think that's the EBA, emergency brake assist.

When you brake hard like at the track, or even in the street sometimes, the ABS system thinks you're going to crash and brakes harder for you this makes the pedal drop and feel mushy.

M2c isn't a track car it's a road car so it has safety systems calibrated for the road which can be a pain sometimes.

[Maynard]

Yes, you need to run an ABS cycle when you flush brake fluid to fully clear and bleed the system; there are handheld code readers that can do it, or ISTA. But then lots of people will tell you they don't ever do this and it works out 'just fine'.

Intermittent wierdness may also be related to brief fluctuations into higher heat range - either minor fluid boil, or pads getting into overheat stage. Can also be the brake assist noted above (but for me the brake assist feels like a harder pedal and more grab, not mushy).

[chmura]

I read on here cant recall where that you need to do a traditional brake bleed without a pressure container that attaches to the master cylinder.

Once you do that the pedal feels better. This is how I bleed all my cars.

[MooMooM2]

Originally Posted by Ratkiller

I flushed the brake fluid twice now (Motul RBF 660) and I'm still experiencing a random mushy pedal under heavy braking when at the track. I'm thinking there may still be an air bubble somewhere in the system, possible the ABS. I recall some cars needing they ABS activated/opened to properly flush the system. Is this the case with the M2C?

maybe it really is the fluid but you are sure its not this?

https://f87.bimmerpost.com/forums/sh....php?t=1885341

[Ratkiller]

Originally Posted by MooMooM2

maybe it really is the fluid but you are sure its not this?

https://f87.bimmerpost.com/forums/sh....php?t=1885341

This is worth looking into. Thanks!

[David1]

I have noticed this brake behavior on both of my M2 cars a 17 and my current 21.

[doughboy]

Originally Posted by Maynard

Yes, you need to run an ABS cycle when you flush brake fluid to fully clear and bleed the system; there are handheld code readers that can do it, or ISTA. But then lots of people will tell you they don't ever do this and it works out 'just fine'.

Intermittent wierdness may also be related to brief fluctuations into higher heat range - either minor fluid boil, or pads getting into overheat stage. Can also be the brake assist noted above (but for me the brake assist feels like a harder pedal and more grab, not mushy).

There's several "safety" brake functions at play, some of which we notice when driving hard or on track:

The pre-emptive brake assist is the one that primes the brakes when you come off the gas very quickly as it assumes an emergency event is happening, this give the tall firm pedal and agressive braking.

The EBA during braking is different, that senses hard braking but then it takes over to put the braking into the ABS zone for you, this results in a unnverving pedal drop sensation in certain situations.

3rd is the brake force distribution to try and keep the car straight under heavy braking, this is linked to the stability program too. You may notice or have to fight a weaving motion under heavy braking, but if you turn off DSC it goes away completely and behaves exactly like a "normal" car.

I've coded out the first two with esys, but the 3rd is beyond me. On a hot dry summer day drive I just turn of DSC and enjoy a more natural feeling car.

I reached out to David daap1193 but didn't get the time to sort it remotely, next year maybe...

[MooMooM2]

Originally Posted by Ratkiller

This is worth looking into. Thanks!

yeah I have to get mine programed because braking is very inconsistant and that is why I mentioned it, it is very similar to what you are feeling. Sometimes the pedal is nice and firm, sometimes the brake point is a bit lower and gives me the feeling of being mushy. Its really fucking annoying. I thought something was wrong till I remembered that thread. Only problems is on track, never experienced it on the street and I had not really noticed it when I was a novice at track but now that I am going deeper in the brakes I can notice it and its super annoying (and in a way feels dangerous)

[MooMooM2]

Originally Posted by doughboy

There's several "safety" brake functions at play, some of which we notice when driving hard or on track:

The pre-emptive brake assist is the one that primes the brakes when you come off the gas very quickly as it assumes an emergency event is happening, this give the tall firm pedal and agressive braking.

The EBA during braking is different, that senses hard braking but then it takes over to put the braking into the ABS zone for you, this results in a unnverving pedal drop sensation in certain situations.

3rd is the brake force distribution to try and keep the car straight under heavy braking, this is linked to the stability program too. You may notice or have to fight a weaving motion under heavy braking, but if you turn off DSC it goes away completely and behaves exactly like a "normal" car.

I've coded out the first two with esys, but the 3rd is beyond me. On a hot dry summer day drive I just turn of DSC and enjoy a more natural feeling car.

I reached out to David daap1193 but didn't get the time to sort it remotely, next year maybe...

really interesting on the 3rd point, totally feel the weaving motion under heavy braking, it also drives me crazy

[Ratkiller]

"The EBA during braking is different, that senses hard braking but then it takes over to put the braking into the ABS zone for you, this results in a unnerving pedal drop sensation in certain situations."

This is it. This is what I'm experiencing. I've got to get this coded out asap.