[SCMTX]

I've searched and searched and can't find the answers I am looking for. I'm running Ferodo ds1.11, stainless lines, Endless RF 650 fluid, AD008Rs (275/305...19s). Heck I even had the coding done on the brakes, steering, diff, MDM. Pressure bled the brakes before each of the past few track days, flused fluid twice in two months.

The lack of pedal consistency (in the brake pedal height) is driving me crazy! I do not experience any fade....the pedal height should not be a pad/fluid/bleeding issue. Heck, I deal with the same issue on the street....sometimes, but not as severe as on track.

Can someone please tell me if there are pad knock back springs available for these calipers somewhere? I would prefer to try this option before dropping $6k for an AP BBK.

Thanks!

[M1500Z]

While I can't answer your question about the availability of AKB springs, I can tell you it's one reason why I made the switch to APs. The larger 2NH caliper seems to just invite more knock-back once the pads get worn to ~60%. The blue brakes seem to have this issue less, and as odd as it may seem, could be an affordable option for you—convert to blue brakes w/ girodisc rotors. Doing that also makes swapping pads much easier in the front, and would save you a little weight.

I really hate to jump to the extreme end, but the AP 9668 setup is really a godsend for these cars if you're comfortable giving up dust boots. You drop ~24lb of unsprung weight, get a massive brake pad, and can run 18" wheels, and of course solve that knock-back issue.

Should you venture down that route, it would be neat to see someone solve that issue on the stock brakes though.

[SCMTX]

Thanks M1500Z. I hadn't thought of switching to the blue brakes up front. I assume they a bolt on option, no special adapters
So, would you say the knock back issue is predominately with the front calipers? To where a front caliper change solves the problem?

[SCMTX]

I guess I can try a couple sets of these..... worst case I get too much drag?

https://www.zeckhausen.com/catalog/i..._217_7351_7352

[M1500Z]

Originally Posted by SCMTX

Thanks M1500Z. I hadn't thought of switching to the blue brakes up front. I assume they a bolt on option, no special adapters
So, would you say the knock back issue is predominately with the front calipers? To where a front caliper change solves the problem?

I don't want to appear as an expert here—only going off my minimum experience with the blue brakes and knowing others who ran them hard at COTA. I would do some digging/ask around to confirm knock-back is less or non-existent on the blue brakes. And yes, it's going to primarily be with the fronts as they see more of the lateral loads—I have APs all around, but the front swap eliminated the knock-back entirely.

You would want the complete set of calipers to avoid any sort of negative bias change. At a glance, Real OEM shows the blue calipers bolt directly to the knuckle so the swap should be easy—calipers, rotors, pads, etc. The master cylinders are the same, and there's a minor coding adjustment to tell the car what brakes it's running. The swap isn't unheard of—M3/4 owners have swapped from CCBs to blue brakes as well.

Originally Posted by SCMTX

I guess I can try a couple sets of these..... worst case I get too much drag?

https://www.zeckhausen.com/catalog/i..._217_7351_7352

I don't know what rate springs AP/Essex use, but I do get audible pad drag. I've heard Zeckenhausen has good customer service—give 'em a ring and pick their brains.

[SCMTX]

Ok thanks, I appreciate the feedback.

[eeyang92]

I have APs in the front - the brake pedal feel is much better and knock-back is eliminated due to the springs. However, are you sure your issue is knock-back, or software-based? One thing I would try is running in DSC-Off mode on track. There is some code in the software that detects rapid accelerator pedal to brake pedal switching as "emergency braking" and it will boost the brake pressure, which will sometimes give you an extremely stiff pedal (and may feel like the brake pedal is higher), and other times you'll have your normal pressure, depending on how fast your switch your feet between the pedals.

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

I'm fairly certain DSC-off turns off this behavior (it is active in all other modes), but I don't recall 100%.

[FaRKle!]

Originally Posted by eeyang92

I have APs in the front - the brake pedal feel is much better and knock-back is eliminated due to the springs. However, are you sure your issue is knock-back, or software-based? One thing I would try is running in DSC-Off mode on track. There is some code in the software that detects rapid accelerator pedal to brake pedal switching as "emergency braking" and it will boost the brake pressure, which will sometimes give you an extremely stiff pedal (and may feel like the brake pedal is higher), and other times you'll have your normal pressure, depending on how fast your switch your feet between the pedals.

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

I'm fairly certain DSC-off turns off this behavior (it is active in all other modes), but I don't recall 100%.

Unfortunately even DSC off doesn't disable the brake boost. You have to code it off.

[eeyang92]

Originally Posted by FaRKle!

Unfortunately even DSC off doesn't disable the brake boost. You have to code it off.

Thanks for the clarification, that's unfortunate!

[MadM2C]

I have the same issue, originally thought it was the pads, but i'm running pagids with the same exact issue.

I also have coding, castrol SRF fluid. Its dumb to spend 6k on the AP kit just for this reason, but i'm getting to that point. I'm fairly convinced that there is no fix to this.

[SCMTX]

Update...

I put StopTech 6.0lb springs in my front calipers, replaced the pads, flushed the fluid with Endless, had the brake coding done. I am going to the track this weekend for a first real test. Very easy to do. I used a little yellow thread cap to cover the hard line when I disconnected my soft brake lines. Dust seals come off pretty easy from the pistons. The pistons pulled out pretty easily by covering them and grabbing them with light pressure with vice grips...no I didn't knick anything up.

Driving on the street things seem to be much better. However, I do still feel like there are some pedal feel differences.

True test will be this weekend....I'm hoping for the best...a 60-70% reduction in the knockback would probably be considered a success.

[SCMTX]

Update # 2...

The StopTech anti-knockback springs solved that problem. No issues and didn't notice any pedal differences or feel over the course of two track days at two different tracks, both high lateral g's and plenty rough enough.

Now of course, my problem is my front rotors are cracking pretty bad around the holes. Bad enough that someone paying attention probably wouldn't let me on track.

So.... track brakes up front and the ability to run 18" wheels....a $10k proposition? Or, just replace rotors and pads more frequently? Giro disks @1400/pair + DTC 60s up front for <$400.

Typing this out, I know my answer. It comes down to afordability for me...Giro disks it is.

I hope this info helps someone with their decisions/delima.

[FaRKle!]

Originally Posted by SCMTX

So.... track brakes up front and the ability to run 18" wheels....a $10k proposition? Or, just replace rotors and pads more frequently? Giro disks @1400/pair + DTC 60s up front for <$400.

Why are track brakes a $10k proposition? You don't have to change the rears.

[medphysdave]

Matching bling

[OG Shark]

Originally Posted by FaRKle!

Why are track brakes a $10k proposition? You don't have to change the rears.

I think he is factoring in the cost of the 18” wheels & tires too.

Originally Posted by medphysdave

Matching bling

Why yes the carpet does match the drapes…

[OG Shark]

Originally Posted by SCMTX

Update # 2...

The StopTech anti-knockback springs solved that problem. No issues and didn't notice any pedal differences or feel over the course of two track days at two different tracks, both high lateral g's and plenty rough enough
.
Now of course, my problem is my front rotors are cracking pretty bad around the holes. Bad enough that someone paying attention probably wouldn't let me on track.

So.... track brakes up front and the ability to run 18" wheels....a $10k proposition? Or, just replace rotors and pads more frequently? Giro disks @1400/pair + DTC 60s up front for <$400.

Typing this out, I know my answer. It comes down to afordability for me...Giro disks it is.

I hope this info helps someone with their decisions/delima.

A little heads up on this part BEFORE next time I ride with you please

[medphysdave]

Originally Posted by OG Shark

I think he is factoring in the cost of the 18” wheels & tires too.



Why yes the carpet does match the drapes…

I'm going to start saving up for a nickel plated set. I figure I'll maximize what I can with stock setup while I figure out when I can start getting more seat time. Private school 🤮 I need a side hustle.

[ashmostro]

Good to know the ST knock back springs actually help the ridiculous OEM calipers. Thanks for the knowledge contribution!

[TUNEDM3]

Great info..do you have a part number for the ST springs?

[GasBurnlife(landapanda)]

Matching nickel plated set would be nice and I also considered it but decided $12k
Is way too much. I continue to run the blue brembo oem calipers with stock rotors and Hawk DTC70s. I used to get a long pedal running SRF after about 15 mins, but since switching to PFC665 that issue went away. It’s been quite eye opening how well the PFC brake fluid works and I wanted to share this finding with my track rat community. Save your money and spend it on more track time instead!

[SOM_M2C44]

Any info on the STOP TECH part number? I am having this same issue and I do not want to spend $10k right now either.

[ashmostro]

He posted the full product page up above guys.

Since he says he used 6 lb springs, it would be these: https://www.zeckhausen.com/catalog/p...ducts_id=22047