Brake pedal travel issue - F80 M3 - Steel Brakes

[patrickd_21]

Hi everyone,

Reaching out for help here as I'm at my wits end with the brakes on this car.

I bought myself a 2016 M3 with 5000 miles on pretty much 1 yr ago exactly. It's my daily and my lapping car at the moment.


When I bought the car, I slapped on some DTC-60 pads, Castrol SRF fluid, and off I went. The car was great all year and I got in 6 events.

The only complaint I had was that the pedal would get a tiny bit soft at the end of a 20min session. Probably due to the stock rubber lines expanding 17min into a hard session. Also, lots of wear on the outside of the tires


So over the winter I went out and bought stainless steel lines and camber plates. Had them installed by a shop, did a brake fluid flush, and was ready to start the year.


HERE is where the problems started.


At my first event, after a warm up lap, I started getting hard on the brakes and almost instantly, the brake pedal became very strange. The first 2-3 inches of pedal did nothing, and then all of my brakes were in the last 1-2 inches. I need to specify here that the pedal feel in the last 2 inches is good. Brakes are rock hard and I can brake HARD going into corners, it's just that since the pedal travel is so long and the brakes are all in the last few inches, modulation is difficult. I can do a full 20 min session going hard braking deep into braking zones, and it does not fade.

When I get off the track and the brakes cool, the pedal feels almost 90% better, but never perfect. I cannot replicate the low engagement point of the brakes in the street.

Here is the list of things I've tried that have had 0 impact on making it better:

- I thought there was maybe air in the system. Bled the system like 10 times. 2-3 times the traditional way. Once with a vaccum bleeder. 3 times with a power bleeder. Bled the ABS 3 times. Did a full fluid flush. I did it about 3 times. Another shop did it twice. Another shop did it 3 times. Another shop did it once

- I thought that since the issues started right after I did the brake lines, maybe it was the lines the issue. Swapped back to stock lines. Brakes still feel terrible, maybe even worse.

- Tried different pads (PFC-08). No difference


I'm getting real tired of this . 3 shops have bleed the brakes. I'm convinced there is no air in the system. I went back to my setup last year when everything was working well and that didn't fix things.

At this point I'm starting to get tired of throwing money at the issue and want to see if anyone has had this problem before. If no one has, my next step will probably be to rebuild the front calipers.

Please help lol

[David0ff]

Originally Posted by patrickd_21

Hi everyone,

Reaching out for help here as I'm at my wits end with the brakes on this car.

I bought myself a 2016 M3 with 5000 miles on pretty much 1 yr ago exactly. It's my daily and my lapping car at the moment.


When I bought the car, I slapped on some DTC-60 pads, Castrol SRF fluid, and off I went. The car was great all year and I got in 6 events.

The only complaint I had was that the pedal would get a tiny bit soft at the end of a 20min session. Probably due to the stock rubber lines expanding 17min into a hard session. Also, lots of wear on the outside of the tires


So over the winter I went out and bought stainless steel lines and camber plates. Had them installed by a shop, did a brake fluid flush, and was ready to start the year.


HERE is where the problems started.


At my first event, after a warm up lap, I started getting hard on the brakes and almost instantly, the brake pedal became very strange. The first 2-3 inches of pedal did nothing, and then all of my brakes were in the last 1-2 inches. I need to specify here that the pedal feel in the last 2 inches is good. Brakes are rock hard and I can brake HARD going into corners, it's just that since the pedal travel is so long and the brakes are all in the last few inches, modulation is difficult. I can do a full 20 min session going hard braking deep into braking zones, and it does not fade.

When I get off the track and the brakes cool, the pedal feels almost 90% better, but never perfect. I cannot replicate the low engagement point of the brakes in the street.

Here is the list of things I've tried that have had 0 impact on making it better:

- I thought there was maybe air in the system. Bled the system like 10 times. 2-3 times the traditional way. Once with a vaccum bleeder. 3 times with a power bleeder. Bled the ABS 3 times. Did a full fluid flush. I did it about 3 times. Another shop did it twice. Another shop did it 3 times. Another shop did it once

- I thought that since the issues started right after I did the brake lines, maybe it was the lines the issue. Swapped back to stock lines. Brakes still feel terrible, maybe even worse.

- Tried different pads (PFC-08). No difference


I'm getting real tired of this . 3 shops have bleed the brakes. I'm convinced there is no air in the system. I went back to my setup last year when everything was working well and that didn't fix things.

At this point I'm starting to get tired of throwing money at the issue and want to see if anyone has had this problem before. If no one has, my next step will probably be to rebuild the front calipers.

Please help lol

I use RBF660 motul with great success

Sometimes late in the 20 min session depending on how hard I push and how thin my pads are I do a "brake check" pedal tap before braking and it brings the pedal rock hard for the upcoming braking zone, try that and it will help you.

[Suds]

One other reason for pedal travel is the brake cylinder pistons are backing away from the calipers, could be from more than one reason. But when you initiate braking you begin refilling the caliper pistons first. Try what David0ff suggested above.

Understand it is very scary to have a car in front you touch the brakes in a high speed corner, when a lift off throttle would slow the car enough for the up coming corners.

So touching the brakes early in a breaking zone won’t make any track day friends.

[BMMMW14]

Agreeing with the above two comments - I think these calipers suffer a lot of of knock back, especially on old seals. If you do rebuild them, you can add springs behind the pistons. Before I did that I was having to brake tap before half the turns in a lap, no problems now

[m4forum]

on stock calipers pedal feel changes is not unusual specially if pads are half live or less. the solution for it is to replace pads sooner what is not economically best alternative or upgrading to BBK. Typically pedal feel changes due heat so brakes are not longer on their happy temperature. Stock caliper have happy temp lower than BBK as expected. Sorry but brake is the single weakness for F80/82 platform.

[Wanted_M]

Have you done the ISTA bleeding procedure? Try that and see if it helps.
https://youtu.be/o7XsCMqZXw0

[2020M2Competition]

Originally Posted by BMMMW14

Agreeing with the above two comments - I think these calipers suffer a lot of of knock back, especially on old seals. If you do rebuild them, you can add springs behind the pistons. Before I did that I was having to brake tap before half the turns in a lap, no problems now

Do you happen to recall what springs you used?

[ellipsis212]

Originally Posted by Wanted_M

Have you done the ISTA bleeding procedure? Try that and see if it helps.
https://youtu.be/o7XsCMqZXw0

I assumed that's what he meant by ABS bleed

[BMMMW14]

Originally Posted by 2020M2Competition

Do you happen to recall what springs you used?

Sure do, they are made by PFC but I got them through the below.


https://alconkits.com/index.php?opti...6051060beaa8b9

[2020M2Competition]

Originally Posted by BMMMW14

Sure do, they are made by PFC but I got them through the below.

https://alconkits.com/index.php?opti...6051060beaa8b9

Thanks

Any issues using them with the stock pistons?

Most aftermarket pistons that use anti-knockback springs are machined to accommodate them like in the picture below

[BMMMW14]

Originally Posted by 2020M2Competition

Thanks

Any issues using them with the stock pistons?

Most aftermarket pistons that use anti-knockback springs are machined to accommodate them like in the picture below

I should add that I swapped in the stainless pistons from racingbrakes.com but no issue at all.

[patrickd_21]

Thanks for the input guys. Just to add to the convo, tried tapping the brakes before the braking zone and it helped marginally. When I swapped pads, I used new pads. But yes the issue was worse with old pads. The brake dust seals are very old crusty.

I had another event in calabogie this past thursday and I noticed that the pistons are MUCH harder to push in on the drivers front side when swapping pads as compared to the rear. I think a caliper rebuild would do it good.

Also, I like the idea of the anti knock back springs. I'll try that and get back to you guys.

[F80Speed77]

Originally Posted by Wanted_M

Have you done the ISTA bleeding procedure? Try that and see if it helps.
https://youtu.be/o7XsCMqZXw0

Almost hate to find out what BMW charges for a brake bleed...

[Suds]

^ $$$, can you imagine if you asked for SRF.

[CanAutM3]

Originally Posted by Suds

^ $$$, can you imagine if you asked for SRF.

My dealer refused to do SRF because it would "contaminate their system".

Ended up buying my own pressure bleeder instead.

[txtrackenthusiast]

I had the same issue with my new-to-me F80 M3 Comp for the past couple of months. I chased the exact same problem in my OG N55 M2. Both cars would not last more than 2-3 laps before I had a spongy pedal, no pressure in the first couple inches of travel, or the worst of it - no pedal at all. I told myself I wouldn't chase it on this car so I bought a set of AP Racing brakes and finally got a chance to run them last weekend. The car was phenomenal and I had ZERO issues on our local 3.1-mile course for 20+ minutes at 10/10ths. I know your pain and can tell you I spent a year bleeding brakes, trying new pads, even switching fluids entirely at every event only to be let down. If it's in your budget I would HIGHLY recommend the AP Racing kit. Here's a link to not so fast but fun lap from this past weekend:

[sly1types]

Try the ISTA ABS bleed, i was having a long pedal and that fixed it.

Edit- i just saw you already did.

This does sound like pad knock back which is really bad on this car.

[NYG]

You need to zero the brake pedal sensor again.

[Mortis]

Originally Posted by NYG

You need to zero the brake pedal sensor again.

I had the same issues at Summit Point this past weekend. New pads (PFC08) and Castrol SRF flush. Brakes only engaging at the very end. It was extremely hot and my calipers went from blue to very dark green. Tried brake management on track, multiple cool down laps during the session, all to no avail. Was wondering whether I boiled the brake fluid, but did not feel like it - braking was still good. How do I reset the brake pedal sensor ?

[bimmerboyE92]

Originally Posted by F80Speed77

Almost hate to find out what BMW charges for a brake bleed...

Dealer is $109 as they've done my F80 in the past and also my daily. They have a machine that they hook up to all calipers and reservoir all at the same time and push a button. The issue is that it is pre-filled with BMW DOT 4.

[jfritz27]

Originally Posted by NYG

You need to zero the brake pedal sensor again.

Is it analogous to what this guy is doing with ISTA to his E90?

(Buried within/part of a DSC recal routine?)

I don't (yet) have a copy of ISTA so can't confirm whether this function is present for our chassis

[NYG]

Originally Posted by Mortis

I had the same issues at Summit Point this past weekend. New pads (PFC08) and Castrol SRF flush. Brakes only engaging at the very end. It was extremely hot and my calipers went from blue to very dark green. Tried brake management on track, multiple cool down laps during the session, all to no avail. Was wondering whether I boiled the brake fluid, but did not feel like it - braking was still good. How do I reset the brake pedal sensor ?

If they went from blue to dark green that day then that means your caliper temps were without a doubt well beyond the boiling point of any fluid. It probably didn't feel like it because unlike other brake fluids, SRF will feel more or less normal once it cools down again and will require some work to reboil. That's why it's so amazing.

I also had green calipers and used PFC pads (08s run a bit hotter than any other pad I used).

I'm not sure how to do the reset on BMWs but if your brakes are only engaging at the end of travel then that would be the first thing I check (brake pressure sensors).