Newbie has soft brake pedal after pad change

[GyroF-16]

Hi guys-
I changed my brake pads from track PFC08s to street pads two weeks ago, and have had a mushy brake pedal ever since...
Of note (this is what I'm worried about)- I popped the hood and checked the brake fluid level by looking through the reservoir before and after I compressed each caliper, but did NOT remove the resevoir cap. Is it possible that I over-pressurized and damaged the master cylinder? Or did I just somehow introduce a little air into the system at the caliper end when swapping the pads? Is air introduction possible or common when changing pads?

Other info & symptoms:
Right after the pad swap, the brake pedal went to the floor the first time I moved the car, but after a few pumps, was nice and firm...
But now the pedal requires a lot of travel to get good brake engagement. If I pump the pedal, it gets firmer, but if I keep pumping, gets a little softer again.
Also, once when starting the car (Z4MC) with the clutch in and shifter in 1st, car jerked (as if in gear) when the starter engaged- like older cars if you tried to start in gear w/ clutch out. That only happened once, though.

The car is still drivable, but brakes aren't any fun to use.

Thoughts and opinions on what's going on?
I plan to bleed the brakes (my first time trying that) when I get back from vacation in about two weeks. But in the meantime him worried about potential master cylinder damage.

[Mirko]

Did you bead the brakes in after the pad change? Wonder if too much material left on the rotors from the track pads causing the new pads to slip and the required pressure increases on the pedal as such?

Maybe before doing that you should change the brake fluid. Best of luck!

Good read/steps on replacing brake pads on our cars.
http://www.pelicanparts.com/techarti...eplacement.htm

How to bleed brakes
http://www.pelicanparts.com/techarti...e_Bleeding.htm

[3002 tii]

Originally Posted by GyroF-16

Hi guys-
I changed my brake pads from track PFC08s to street pads two weeks ago, and have had a mushy brake pedal ever since...
Of note (this is what I'm worried about)- I popped the hood and checked the brake fluid level by looking through the reservoir before and after I compressed each caliper, but did NOT remove the resevoir cap. Is it possible that I over-pressurized and damaged the master cylinder? Or did I just somehow introduce a little air into the system at the caliper end when swapping the pads? Is air introduction possible or common when changing pads?

Other info & symptoms:
Right after the pad swap, the brake pedal went to the floor the first time I moved the car, but after a few pumps, was nice and firm...
But now the pedal requires a lot of travel to get good brake engagement. If I pump the pedal, it gets firmer, but if I keep pumping, gets a little softer again.
Also, once when starting the car (Z4MC) with the clutch in and shifter in 1st, car jerked (as if in gear) when the starter engaged- like older cars if you tried to start in gear w/ clutch out. That only happened once, though.

The car is still drivable, but brakes aren't any fun to use.

Thoughts and opinions on what's going on?
I plan to bleed the brakes (my first time trying that) when I get back from vacation in about two weeks. But in the meantime him worried about potential master cylinder damage.

Pedal going to floor right after a brake job is normal. Assuming you didn't open the lines or open the bleeder valves, I don't see how you got air into the system.

[dc_wright]

Originally Posted by 3002 tii

Pedal going to floor right after a brake job is normal. Assuming you didn't open the lines or open the bleeder valves, I don't see how you got air into the system.

^This^

Usually takes 2-3 full pumps to refill the calipers and move the brake pads from the fully recessed position to against the rotors. It should NOT however have any effect on the clutch operation. I think you're on the right track with a brake bleed. I'd also inspect the clutch slave cylinder for any leakage to ensure it's not a source of air getting into the system. Regular maintenance schedule with OEM fluid is a full system flush every two years, with high temp fluid it's yearly at a minimum so if you haven't done it for a while you're due anyway.

[GyroF-16]

Thanks for the responses.
Put new Castrol SRF in about 6 weeks ago, same time as the PFC08 install, and had brakes bled the same day. Had a nice firm pedal then, both before and after the HPDE I did at the end of May. The pedal firmness changed to softness after I did the pad change 2 weeks ago.
Any additional input is welcome.
I'll plan to bleed the brakes in about 2 weeks when I'm back in town.

[The HACK]

Go and do a couple of stops and activate the ABS pump, then bleed and see if that helps.

Also, if your street pads have worn down further than the track pad, there may be some "retraction" of the pad causing the pedal to travel further than the track pad. I don't know how exactly to explain it.

Lastly, street or organic pads are simply "softer" than high metallic content track pads, requiring a little more pad pressure to supply the same "bite." If you got used to the track pad's pedal stiffness then the street pad may cause the pedal to feel a little "softer."

Or it could be a combination of all of the above.

And you may not like to hear this, but I have friends with E36 M3s that swear that their brake pedals are never the same after their first pad change or fluid, no matter what they do. Something about BMW brakes I guess.

There are some extra steps that i do SOMETIMES before I swapped over to fixed calipers to bleed/flush BMW brakes. Usually I use a pressure bleeder like the Motive bleeder attached to the reservoir so I would never run out of fluid, but ALSO if I ever experience a soft pedal after a bleed/flush/pad change, I elicit a friend to do the pump/open/close/pump routine until the pedal is firm again. Just make sure the pedal never goes all the way to the floor when you pump and you're golden.

One LAST thing (I'm just full of last things) to add. Usually, especially back in the sliding caliper days, as soon as I'm done with the pad change, even before I switch the car on, I would pump the pedal until it's firm before I turn the key. Don't know if this will help, get in the car with the keys out, pump the pedal a few times until it's rock solid, then start the car. See if the pedal feel returns. Don't know why, but this often times work for me that, completely out of habit now, I always pump the brake twice before I start ANY car (it's also just to check and see if the brakes work before I start) even the electric, which is absolutely not necessary.

[GyroF-16]

Originally Posted by The HACK

Go and do a couple of stops and activate the ABS pump, then bleed and see if that helps.

Also, if your street pads have worn down further than the track pad, there may be some "retraction" of the pad causing the pedal to travel further than the track pad. I don't know how exactly to explain it.

Lastly, street or organic pads are simply "softer" than high metallic content track pads, requiring a little more pad pressure to supply the same "bite." If you got used to the track pad's pedal stiffness then the street pad may cause the pedal to feel a little "softer."

Or it could be a combination of all of the above.

And you may not like to hear this, but I have friends with E36 M3s that swear that their brake pedals are never the same after their first pad change or fluid, no matter what they do. Something about BMW brakes I guess.

There are some extra steps that i do SOMETIMES before I swapped over to fixed calipers to bleed/flush BMW brakes. Usually I use a pressure bleeder like the Motive bleeder attached to the reservoir so I would never run out of fluid, but ALSO if I ever experience a soft pedal after a bleed/flush/pad change, I elicit a friend to do the pump/open/close/pump routine until the pedal is firm again. Just make sure the pedal never goes all the way to the floor when you pump and you're golden.

One LAST thing (I'm just full of last things) to add. Usually, especially back in the sliding caliper days, as soon as I'm done with the pad change, even before I switch the car on, I would pump the pedal until it's firm before I turn the key. Don't know if this will help, get in the car with the keys out, pump the pedal a few times until it's rock solid, then start the car. See if the pedal feel returns. Don't know why, but this often times work for me that, completely out of habit now, I always pump the brake twice before I start ANY car (it's also just to check and see if the brakes work before I start) even the electric, which is absolutely not necessary.

Hack-
Thanks for all the suggestions!

The street pads I put in were new PFC "Z compound" - I hope they're better than OEM, but, with the pedal feel issue, I'm not sure yet...

Copy the E36 M3 thing- I drove a 99 M3 for 14 years, and I'd agree- the pedal was never the same after the first fluid change... but this M Coupe has has several fluid changes (3 or 4 since I've owned it), and it's never been an issue - until this pad change.

I'll take your advice and get into the ABS before I bleed the brakes next week. And will keep the manual pumping option in mind after I pressure bleed them.

And good tip on pumping the pedal before start - I'll start making that a habit.

Thanks again for all the input - I appreciate it.

Gyro

[GyroF-16]

Ok- here's my update:
I never found time to bleed the brakes.
I concluded that the issue was the "engagement point" in pedal travel- that is, I had to push further (than with my track pads) to get brake engagement, and even further to get full braking. Enough that I felt like the pedal was at the bottom of travel. This changed the pedal-height relationship between the brake pedal and the throttle, making heel & toe downshifts more difficult, as the brake was "below" the throttle under moderate to heavy braking.
Today I put my track pads (PFC-08) back on in preparation for a BMWCCA driver's school I'm doing on Saturday.
When doing the swap, I noticed that the street pads (PFC Z-compound) are noticeably thinner (by about 4-5mm) than the PFC-08s that I'm putting back on. I don't think this is due to wear- I've only got about 3,000 highway miles on the Z-compounds. I think the Zs started out thinner.
Also, my rotors are worn near the limits and will be replaced shortly after this track day.
With the track pads on, the soft pedal and lower engagement point are gone. (At least during my short test drive and the brake bedding series of stops). So the brake system and fluid are fine.
Question:
Could the thinner street pads, combined with the worn rotors, cause this noticeably-increased pedal travel and lower engagement point with the Z-compound street pads?
If so, is this anything I can change?
Would bleeding the brakes when swapping back to the street pads change the engagement point? Or will the calipers always retract to the same point, meaning that thinner pads will require more pedal movement before they come into contact with the rotors?

Gyro

[longress]

As mentioned pad compound can change the friction to where more pedal travel may be required. Thin rotors won't effect this but it's possible you may be getting some knock back which could result in more travel.
I have some ecs rotors, brass caliper bushings and some PFC 8 pads I can no longer use since I went bbk. I'm just north of you so let me know if your interested and we could meet up.

[dc_wright]

Originally Posted by GyroF-16

Ok- here's my update:
I never found time to bleed the brakes.
I concluded that the issue was the "engagement point" in pedal travel- that is, I had to push further (than with my track pads) to get brake engagement, and even further to get full braking. Enough that I felt like the pedal was at the bottom of travel. This changed the pedal-height relationship between the brake pedal and the throttle, making heel & toe downshifts more difficult, as the brake was "below" the throttle under moderate to heavy braking.
Today I put my track pads (PFC-08) back on in preparation for a BMWCCA driver's school I'm doing on Saturday.
When doing the swap, I noticed that the street pads (PFC Z-compound) are noticeably thinner (by about 4-5mm) than the PFC-08s that I'm putting back on. I don't think this is due to wear- I've only got about 3,000 highway miles on the Z-compounds. I think the Zs started out thinner.
Also, my rotors are worn near the limits and will be replaced shortly after this track day.
With the track pads on, the soft pedal and lower engagement point are gone. (At least during my short test drive and the brake bedding series of stops). So the brake system and fluid are fine.
Question:
Could the thinner street pads, combined with the worn rotors, cause this noticeably-increased pedal travel and lower engagement point with the Z-compound street pads?
If so, is this anything I can change?
Would bleeding the brakes when swapping back to the street pads change the engagement point? Or will the calipers always retract to the same point, meaning that thinner pads will require more pedal movement before they come into contact with the rotors?

Gyro

I missed earlier that you had installed the PFC Z rated pads. Sorry for that! Any difference in pad thickness would only be felt on the very first pump of the brake pedal after they were installed. After that it should make no difference. On the Z rated pads PFC installs an anti squeal buffer plate that's crimped on the the pad backing plate (see photo). What I found when I had them on my car is that anti-squeal plate acts like a thin spring and pushed to pad back a bit farther than you'd get without it. This causes a bit more pedal travel to close the gap and get the pads into compression against the rotor and the result is added brake pedal travel. I liked the performance of the PFCZ pads but hated the added brake pedal travel. When I swapped them out for a set of Hawk pads the pedal travel immediately went back to normal. If I ever decide to put them back on, I'm going to peel that anti-squeal plate off them and live with any noise that may come instead of the added pedal travel.

[GyroF-16]

Originally Posted by dc_wright

I missed earlier that you had installed the PFC Z rated pads. Sorry for that! Any difference in pad thickness would only be felt on the very first pump of the brake pedal after they were installed. After that it should make no difference. On the Z rated pads PFC installs an anti squeal buffer plate that's crimped on the the pad backing plate (see photo). What I found when I had them on my car is that anti-squeal plate acts like a thin spring and pushed to pad back a bit farther than you'd get without it. This causes a bit more pedal travel to close the gap and get the pads into compression against the rotor and the result is added brake pedal travel. I liked the performance of the PFCZ pads but hated the added brake pedal travel. When I swapped them out for a set of Hawk pads the pedal travel immediately went back to normal. If I ever decide to put them back on, I'm going to peel that anti-squeal plate off them and live with any noise that may come instead of the added pedal travel.

D.C.-
Thank you for that information on the Z-compounds... it's nice to hear that someone else had this pedal-travel issue (and it's not caused by something I did...).
I may try to peel the backing plates off as you describe... if not, the instructor I had at yesterday's driving school seemed happy with the Cool Carbons that he used for street driving on his E46 M3, so I may try some of those.

Thanks again to all...

[dc_wright]

Originally Posted by GyroF-16

D.C.-
Thank you for that information on the Z-compounds... it's nice to hear that someone else had this pedal-travel issue (and it's not caused by something I did...).
I may try to peel the backing plates off as you describe... if not, the instructor I had at yesterday's driving school seemed happy with the Cool Carbons that he used for street driving on his E46 M3, so I may try some of those.

Thanks again to all...

I tried the Cool Carbons on our E46. Performance was good, but they were just as dusty if not more so than OEM pads. If you're going to swap between track pads and street pads you might want to look at Akebono Euro ceramics for your street pads. They're strictly street pads, but they're silent and virtually dustless. If you're going to do the street/track pad swap you might as well get some benefit from the street pads.

[GyroF-16]

Originally Posted by dc_wright

I tried the Cool Carbons on our E46. Performance was good, but they were just as dusty if not more so than OEM pads. If you're going to swap between track pads and street pads you might want to look at Akebono Euro ceramics for your street pads. They're strictly street pads, but they're silent and virtually dustless. If you're going to do the street/track pad swap you might as well get some benefit from the street pads.

Thanks again, DC. My track pads (PFC-08s) have lots of initial bite, and I'm becoming quite addicted to it... the Cool Carbons reportedly also have good initial bite (for a street pad). So I'm willing to live with some dust if that's what it takes. But if the dust becomes annoying, I certainly have the Akebono's in mind.

[dc_wright]

Then you probably won't like the feel of the Akebono's or any of the ceramics for that matter. With the ceramic pads you give up some of the initial bite in exchange for low/no dust.