[ZM2]

Originally Posted by KHAP13

Has anyone experienced an inconsistent brake pedal feel with the OG M2 on track? I have done a lot of research but could only find discussions of this issue on an E90 thread, an talks about ice pedal in Porsche threads, which doesn't seem to be my case.

I have noticed variations between how firm the pedal is during braking on the same lap -- some corners it is very firm and confidence inspiring, others not so much. My perception is it has to do with how quickly I apply the brakes. It seems that if I am very quick/aggressive on the brakes I am usually met with firm pedal, but if I am a little less aggressive I get a longer feeling less confidence inspiring spongyish feel. It can be softer in one corner and firm in the next on the same lap. It feels similar to when brake fluid gets too hot, but since the feel alternates between braking zones I don't think the fluid is the issue.

Alos, it does not appear that stopping power is impacted much (Looking at data from RaceChrono and judging by braking points), but the inconsistent feel makes it really hard to trust, and is a bit annoying.

If I had to guess, I would say its related to how much the system is boosting the brake pressure.... maybe a system reaction to certain preemptive or reactive ABS conditions (never felt ABS pulsing in the pedal). Or something related to safety system like the collision avoidance...Other things I have considered is pad knock back (does that happen on these brakes?).

I have bled the system a few times with Motive power bleeder (although I don't have the software for bleeding the ABS block), and never had air bubbles in the lines.

-Manual 2018 M2 with RSL29, RBF600, Cup 2s, otherwise stock car.
-Happens in Sport+ and DSC off (haven't tried other modes)
-Tracks Hockenheim and Nurburgring GP (both pretty had on brakes IMO).

I am really at a loss for how to make the situation better. Any thoughts or advice are greatly appreciated. Thanks!

I ran Pagid's a couple years ago and didn't like them. The bite, feel, and fade resistance of PFC's are much better. I noticed the Pagid would act similar to what you're describing if you're using the brakes pretty hard.

Also, I noticed the Pagid's required a good bedding in to have full, consistent stopping power, or issues like you're mentioning would happen when first getting on track. The PFC's didn't require any bedding and were ready to go after a good warm up lap.

This may/may not be your issue, but just letting you know what I experienced.

If you do switch to a different track pad compound, be careful going deep on the brakes until you're certain you've removed the previous pad's material from the disc, and the new pad material has transferred to the disc. Don't ask me how I learned this.

Nothing bad happened, just a big Code Brown moment and good training to learn how to take the run off road if you ever have brake issues! And from my two days on the Ring, I distinctly remember no run off space on the Nordschleife(!), so I'm sure this is not confidence inspiring at all.

Try PFC 08 or 11's and run them at Hockenheim before the Ring is my advice.

[bentom2]

I’ve noticed this as well, KHAP13. It seemed to be related to my inputs rather than heat or other external factors. When I was too abrupt on the brake, I’d be met with a higher engagement point. When I switched to braided lines and the bite point under normal braking conditions moved up, it seemed to go away, probably because I no longer had the extra give to push through and was forced to be more deliberate in my inputs to avoid ABS at every stop.

Re ZM2’s pad comments: I also noticed I would have to apply more pedal pressure toward the end of a session than the beginning on RSL29s. Looking at the friction table for them, I see why now; friction falls off above 500c.

I’m running PFC08’s currently and bite point is much more predictable throughout, even during some open track, drive until the gas light comes on, events I’ve done recently. I like this aspect of the PFC08, but they have so much bite, that there’s a very narrow pressure window from brushing the pedal to load the front tires, to full abs engagement, especially on the rear. I find it a bit more challenging than I’d prefer to modulate within that zone. It’s probably only a few pounds difference at the pedal.

I might try RSL1s next if I don’t adjust to the 08s by the time they’re ready to replace. Looks like a flatter plot throughout the temp range, but not sure how they compare for bite to the PFC08’s

ZM2 - how many sets of PFC08s can you run before replacing rotors? I was able to run 4 sets of RSL29s. Just curious what I’m looking at for rotor-friendliness.

[ZM2]

Originally Posted by bentom2

I’ve noticed this as well, KHAP13. It seemed to be related to my inputs rather than heat or other external factors. When I was too abrupt on the brake, I’d be met with a higher engagement point. When I switched to braided lines and the bite point under normal braking conditions moved up, it seemed to go away, probably because I no longer had the extra give to push through and was forced to be more deliberate in my inputs to avoid ABS at every stop.

Re ZM2’s pad comments: I also noticed I would have to apply more pedal pressure toward the end of a session than the beginning on RSL29s. Looking at the friction table for them, I see why now; friction falls off above 500c.

I’m running PFC08’s currently and bite point is much more predictable throughout, even during some open track, drive until the gas light comes on, events I’ve done recently. I like this aspect of the PFC08, but they have so much bite, that there’s a very narrow pressure window from brushing the pedal to load the front tires, to full abs engagement, especially on the rear. I find it a bit more challenging than I’d prefer to modulate within that zone. It’s probably only a few pounds difference at the pedal.

I might try RSL1s next if I don’t adjust to the 08s by the time they’re ready to replace. Looks like a flatter plot throughout the temp range, but not sure how they compare for bite to the PFC08’s

ZM2 - how many sets of PFC08s can you run before replacing rotors? I was able to run 4 sets of RSL29s. Just curious what I’m looking at for rotor-friendliness.

That's a good question and one that I've forgotten the exact answer to, as I was running PFC's with the OEM blue brakes 3-yrs ago before moving to AP's with Ferodo's.

What I do remember is I like the PFC 11 even more than the 08. The bite is even better than 08, but the feel is also better and more controllable, IMO.

And, the 11s are more rotor friendly than the 08s. It seemed like life of the 11s were about 3/4 that of the 08s, so I'm guessing rotor and pad replacement costs between running the 08 & 11 is a wash.

The PFC 11 is still my fav pad, with the Ferodo DS3.12 right there with it.

[peterbigblock]

Just an observation, there's a lot of consideration given to Castrol SRF that I think misses a substantial point. The main benefit of SRF is it's high wet boiling point -- if you don't flush fluid very often, it fares better than most other racing fluids.

A much better regimen, which I see a lot of people on here recommending, is to flush racing fluid before a track event. In that case, SRF is at a disadvantage as its dry boiling point is lower than other top-of-the-line racing fluids (Motul RBF660 is 617ºF, CMS RF1 is 622ºF, SRF is 590ºF). It's not a huge difference, but given the high cost and on-and-off availability of SRF, it's worth noting that changing your fluid often using the higher DBP stuff is better all around.

My two cents. Carry on!

[mauisr]

Originally Posted by Nick340

Hello,

Considering trading 340i in for an M2.

Daily driver plus 2-3 track days a year.

I've heard the brakes are pretty terrible on track and wondered if anyone can give experience?

Also read M performance fluids and pads can improve?

Or after market pads like pagid?

Hi, i have an m2 comp, in my case I'm between of intermediate to advance driver
I screwed up my OEM brakes in 5 track days, they are like butter, cant handle hight temperatures, so use them up until you start to warp them, it will be useful to learn to handle the car, and after that comsider an aftermaket big brake front kit

Greeting

[HP Autosport]

Originally Posted by mauisr

Hi, i have an m2 comp, in my case I'm between of intermediate to advance driver
I screwed up my OEM brakes in 5 track days, they are like butter, cant handle hight temperatures, so use them up until you start to warp them, it will be useful to learn to handle the car, and after that comsider an aftermaket big brake front kit

Greeting

Upgraded pads such as the Ferodo DS1.11 with high-temp brake fluid will do the trick for most people.

A true two-piece rotor from Paragon or Girodisc with more curved vanes can also help.

That said, nothing beats a proper BBK from AP, Brembo or Stoptech. PM us if you have any questions or is looking for a set.

[medphysdave]

Originally Posted by peterbigblock

Just an observation, there's a lot of consideration given to Castrol SRF that I think misses a substantial point. The main benefit of SRF is it's high wet boiling point -- if you don't flush fluid very often, it fares better than most other racing fluids.

A much better regimen, which I see a lot of people on here recommending, is to flush racing fluid before a track event. In that case, SRF is at a disadvantage as its dry boiling point is lower than other top-of-the-line racing fluids (Motul RBF660 is 617ºF, CMS RF1 is 622ºF, SRF is 590ºF). It's not a huge difference, but given the high cost and on-and-off availability of SRF, it's worth noting that changing your fluid often using the higher DBP stuff is better all around.

My two cents. Carry on!

This is a very good point. I run SRF because I don't plan to change fluid often. It's the reason I chose SRF. If I were running track days frequently I'd opt for a different fluid and more frequent fluid changed. Everyone seems to go to SRF as "the best", and I think it's good to note the scenario where it shines the most. My SRF will get changed at the 2yr mark.

[HP Autosport]

Originally Posted by medphysdave

This is a very good point. I run SRF because I don't plan to change fluid often. It's the reason I chose SRF. If I were running track days frequently I'd opt for a different fluid and more frequent fluid changed. Everyone seems to go to SRF as "the best", and I think it's good to note the scenario where it shines the most. My SRF will get changed at the 2yr mark.

If you have the ability to flush the brake hydraulic system before each track day, most of the other high-temp brake fluid is the way to go. If not, SRF is the go-to for a track season.