soft pedal

[chip]

Have an '87is that I tracked back in Nov- put some cool carbon pads on and super blue fluid for the event, also running SS lines. The car stopped ok, but the pedal had more travel than I would like. After the event I replaced my MC (oem/new) and rebuilt on the calipers hoping that this would firm the pedal up some. While doing the work I noticed that the inside pads on the rear where not as worn as the outsides, they appeared to be hardly used, whereas the piston sides where much thinner. The front pads had even wear. Just recently I bleed the lines again- got a few bubbles out- but not much and also installed some brass caliper bushings. None of this has helped, and the pedal still feels soft. It does firm up some if I give a quick pump. I have not seen any leaks.
Could the new MC be bad?
What else could I check?

[jlevie]

That sounds like it might be back-out of the caliper pistons while the car is traveling at speed. A bit of warp or wobble in the rotors will cause the pistons to retract a bit, resulting in a bit more motion of the pedal when hitting the brakes. A quick pump of the pedal prior to full application of braking pressure will raise and firm up the pedal.

[Massive Lee]

Did you bleed front and back? How thoroughly and expertly did you bleed?

Lee

[chip]

That sounds like it might be back-out of the caliper pistons while the car is traveling at speed. A bit of warp or wobble in the rotors will cause the pistons to retract a bit, resulting in a bit more motion of the pedal when hitting the brakes. A quick pump of the pedal prior to full application of braking pressure will raise and firm up the pedal.

I heard that this may be the issue- the rotors seem fine- the backs were new right before the Nov school. Is there any way to correct this?

[chip]

Did you bleed front and back? How thoroughly and expertly did you bleed?

Lee

I use a pressure bleeder, and also did some pedal pumping inbetween. RR, RL, FR, FL sequence. I may try and crack the ABS lines while under pressure- see if any air is trapped there.

[jlevie]

This happens to my Spec E30 after a weekend or two and disappears when I fit new rotors after the third or fourth weekend. I know that it isn't air in the system and your use of a pressure bleeder would tend to make air unlikely. It takes very little warp or wobble to knock the pads far enough back to be noticeable in the pedal.

[chip]

This happens to my Spec E30 after a weekend or two and disappears when I fit new rotors after the third or fourth weekend. I know that it isn't air in the system and your use of a pressure bleeder would tend to make air unlikely. It takes very little warp or wobble to knock the pads far enough back to be noticeable in the pedal.

Is the warp so minimal that you won't feel this in the pedal to begin with? I guess I'll replace the front rotors (the rear rotors are new-Brembo) and see what happens. Any thoughts on the different pad wear thickness on the rear?
What pads do you run- I've got some HT10 that I'm going to try

TIA
Chip

[CAOSyAMOR]

happened to me on my CBR1000RR. After a 'minor' collision I repaired the bike myself but could not immediately figure out why my pedal feel was so soft. Turned out my front rotors were very slightly warped. Could not be seen accurately by the eye alone. I replaced the rotors and bingo.

[jlevie]

Is the warp so minimal that you won't feel this in the pedal to begin with? I guess I'll replace the front rotors (the rear rotors are new-Brembo) and see what happens. Any thoughts on the different pad wear thickness on the rear?
What pads do you run- I've got some HT10 that I'm going to try

When I see this there are not any visible signs of warp or vibration in the brake pedal. Just a lot (and I mean a lot) of surface cracks in the rotors.

I use PCF-01 or PFC-06 pads. The 06 compound is good for an Enduro as it wears at a slower rate than the 01 compound. But the 01 compound has a bit more bite and thus is better in a Sprint race. I used to use HT-10's until James Clay (of Bimmerworld) turned me on to the PFC pads. I find that they provide a better pedal feel and slightly better braking.

[chip]

Last night put some power slot rotors on (nieghbor just happened to have a set laying around), the HT10 and bleed the system again. Seemed to do the trick- the front rotors had some cracks in them and they did have some high spots that dragged on the pads.

Now I'm ready for the track next weekend- yeah

Jim- thanks for the input- Like I said this was what someone else suggested, but did not have a reason for why it happens or how to fix the push back issue.

Chip

[jlevie]

Outstanding!