Soft Brake Pedal Feel

[Mach3M3]

Hey guys,

I am at my wit's end with this. My brake pedal feels absolutely awful. I need to press about half-way on it or more to get decently into my brakes.

I thought this maybe air in the ABS system so I did an INPA bleed, didnt help at all.

I've got brand new Castrol SRF in the lines, relatively new PFC 08 pads. Nothing helps. The car inspires zero confidence under brakes and it's really frustrating.

How does everyone else's pedal feel? Like I said, I need to get about 1/2-3/4 into the brakes for them to do much and the pedal just feels so soft on the way in.

[spidertri]

What's your brake setup, stock calipers and rotors? Any specific class you have to adhere to? Any ducting?

Do the brakes feel any better once the pads have some heat in them?

Coded off all the normal settings?

[Mach3M3]

stock calipers, PFC 08, high carbon centric blanks. Also have stainless lines.

Brakes are open but i dont think anything is wrong with the stock setup since my buddy that runs his car in TT5 (he's on here) is on the same setup with no issues.

All the documented stuff coded out.

It's not a braking problem, its a brake feel problem. They feel terrible just standing still with the engine idling.

[tracer bullet]

Even if you're sure they are bled OK I'd consider doing it one more time. Easiest solution. Pressure bleed and get that stuff streaming out, maybe even knock the calipers with a rubber mallet. It's got to be flowing faster than a bubble can work its way back up the line. Knowing you replaced the lines, clearly air got in there. Chasing it out can be a huge pain in the butt. Been there!

Next thing to look into = could be a master cyclinder issue?

You mentioned standing still so potentially ruling out the pads. They may be better warm and less bite cold but not the issue the way you are describing.

[spidertri]

Yeah, if there is no firm pedal when sitting there idling then it sounds like a bad master cylinder. PO of my car changed the MC before 85k miles because it was worn out.

I run PFC08s on track with front E90 330i calipers and discs and they are fantastic. I can brake late and hard and catch a lot of people in braking zones. I did have to add brake ducts though, I was seeing overheating by the end of a session.

[Mach3M3]

yeah my car is at around 86k miles.

thinking more about it, i dont remember the pedal feeling this bad last year so I do think the MC is worn out.

[amg6975]

If the system went totally dry it takes several INPA bleeds and some manual bleeding to get all the air out. It's a total PITA. I've noticed the INPA bleed can create really small bubbles that linger in the system for a while.

Make sure you do manual bleeding with someone pushing the pedal, the fluid moves much more forcefully than doing a power bleed so more air will come out.

I've also found that just driving around and lighting up the ABS seems to help sometimes too.

[Mach3M3]

Originally Posted by amg6975

If the system went totally dry it takes several INPA bleeds and some manual bleeding to get all the air out. It's a total PITA. I've noticed the INPA bleed can create really small bubbles that linger in the system for a while.

Make sure you do manual bleeding with someone pushing the pedal, the fluid moves much more forcefully than doing a power bleed so more air will come out.

I've also found that just driving around and lighting up the ABS seems to help sometimes too.

All of the bleeding i've done has been the two person method: one person pushing down on the pedal, the other operating the nipple on the caliper. I dont see how a pressure bleeder will do a better job than that.

I've done that form of bleeding 2-3 times now, in addition to 1.5 INPA corner bleeding. And in between that, I've done a track weekend and autox with plenty of ABS activation. So any air built up in the system, should have been bled out by now.

The more i think about it, the more I think my master cylinder is dying.

[Mach3M3]

Update: Did a power bleed of all 4 corners. Pedal felt the same.

Moved on to replacing the master. 4 hours later...pedal feels the same.

I am either over-sensitive to how the brake pedal feels, or there is some sort of controls issue where the DSC is giving the pedal too much slack.

I am going to double check my coding parameters and will also do the DSC calibration through ISTA to see if that fixes the issue.

[amg6975]

Originally Posted by Mach3M3

All of the bleeding i've done has been the two person method: one person pushing down on the pedal, the other operating the nipple on the caliper. I dont see how a pressure bleeder will do a better job than that.

I've done that form of bleeding 2-3 times now, in addition to 1.5 INPA corner bleeding. And in between that, I've done a track weekend and autox with plenty of ABS activation. So any air built up in the system, should have been bled out by now.

The more i think about it, the more I think my master cylinder is dying.

Got my comment mixed up. I was saying the two person method is better. 2-3 times and 1.5 INPA procedures is not all that much. When I let my system go dry it took at least 5 INPA bleeds with full manual bleeds between. Air just kept coming out, it was driving me nuts.

I doubt it's a DSC issue, the system is mechanical until it needs to intervene. Maybe a valve issue inside the DSC but that would be a new one to me.

If you think it's just you being picky or whatever try an M3 master cylinder, that should improve the feel a bit.

[spidertri]

Did you INPA bleed after the MC swap?

Have you driven his or had your friend drive your car to compare?

[Mach3M3]

Update #3: brakes do feel better now that i am actually driving the car. Unsure if it was the MC swap, the DSC recal or both. But I do think they feel better.

I have had a friend with a 128 drive it and also felt the brakes were feeling weird.

[Scott_Tucker]

Originally Posted by Mach3M3

Update #3: brakes do feel better now that i am actually driving the car. Unsure if it was the MC swap, the DSC recal or both. But I do think they feel better.

I have had a friend with a 128 drive it and also felt the brakes were feeling weird.

How are your brakes? Are they still performing normally? I'm having the same problem with my 135is.