Brake Pedal Travel

[eacmen]

Background: OEM calipers with track pads. Track event in March, pedal started to engage lower. But fluid was ok, and brakes continued to work. Finished the weekend but went easy on the brakes. After that event installed brass caliper guide bushings and SS brake lines. Bled 1.5 liters of SRF through the whole system. Same pedal travel.

Curious if others experience the same brake pedal travel that I do. When the engine is off I can pump the brake pedal and it is rock hard. Maybe 1/2 inch of travel before it gets hard. I can stand on it and it doesn't move.

But if I keep the pressure on the brake pedal, start the engine, the pedal sinks *significantly* approximately 1/2 inch below the throttle. And my brake engagement point is also pretty far. The brakes work and there is engagement but the pedal travel just seems long.

The front pads had some slight pad taper to them which I am hoping the brass guides will fix. Havent had time to take the car out and wail on them to get the front pads flat. Could a tapered pad cause long travel?

[Feffman]

Just spent some time researching this issue with my M3. If you are bumping over the curbs at the track, you are probably getting brake pad "knock back". Easy thing to do is a simple very light tap on the brakes just before getting into the braking zone/turn to set the pads.

Feff

[timmo]

Sounds like it could be pad taper. My thoughts are that if the pads are being forced straight, the extra dead spot is due to taking up the slack where only one edge of the pad is being used at first.

I have severe pad taper on one caliper and swapped them left/right, and after that the pedal was horrible. Brass bushings are on their way

[eacmen]

Sounds like it could be pad taper. My thoughts are that if the pads are being forced straight, the extra dead spot is due to taking up the slack where only one edge of the pad is being used at first.

I have severe pad taper on one caliper and swapped them left/right, and after that the pedal was horrible. Brass bushings are on their way

Wow that is some serious taper. Mine were tapered the other way (top-to-bottom).

[r4dr]

Sounds like it could be pad taper. My thoughts are that if the pads are being forced straight, the extra dead spot is due to taking up the slack where only one edge of the pad is being used at first.

I have severe pad taper on one caliper and swapped them left/right, and after that the pedal was horrible. Brass bushings are on their way

My pads looked like this if not worse before I switched to brass bushings on the E30. I just swapped my PFC08s out last week, the wear is now as straight as possible. Make sure to clean + grease the pins every event or two, probably overkill but nothing to me is overkill when it comes to brakes. I use Redline CV2 to grease them. I also found brake pedal feel is more direct, which makes sense since there's no rubber to dilute pedal feedback.

[timmo]

My pads looked like this if not worse before I switched to brass bushings on the E30. I just swapped my PFC08s out last week, the wear is now as straight as possible. Make sure to clean + grease the pins every event or two, probably overkill but nothing to me is overkill when it comes to brakes. I use Redline CV2 to grease them. I also found brake pedal feel is more direct, which makes sense since there's no rubber to dilute pedal feedback.

Got my brass bushings in, but have a question.

How much play was there between the bushing and the caliper? You can easily slide the bushing back and forth axially between the shoulder and the circlip, as there is an extra 3-4 mm in length than the caliper itself (seen in pic below). Seems like that fitment is looser than the bushing to the pin itself, so I would think the caliper would slide on the bushing before the pin on the bushing.



Also interestingly enough, I did 1 more trackday with the pads swapped left/right and the taper is now gone, both sides are more or less worn even.

[eacmen]

Got my brass bushings in, but have a question.

How much play was there between the bushing and the caliper? You can easily slide the bushing back and forth axially between the shoulder and the circlip, as there is an extra 3-4 mm in length than the caliper itself (seen in pic below). Seems like that fitment is looser than the bushing to the pin itself, so I would think the caliper would slide on the bushing before the pin on the bushing.



Also interestingly enough, I did 1 more trackday with the pads swapped left/right and the taper is now gone, both sides are more or less worn even.

If i remember correctly there was some play in the bushing itself. But not that much. That brass bushing looks really long tho. Ours ended at the ridge for the circlip.

The fact that there is movement in the bushing shouldn't matter much.


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[timmo]

If i remember correctly there was some play in the bushing itself. But not that much. That brass bushing looks really long tho. Ours ended at the ridge for the circlip.

The fact that there is movement in the bushing shouldn't matter much.


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Okay, I guess I'll keep my eye on pad wear and bushing OD wear against the caliper itself. As long as the pads wear straight and the bushing movement in the caliper doesn't affect it, I'll be happy.

Yeah I bought longer ones from Condor Speed Shop because they're about the same length as the stock ones. They provide a rubber cap so in theory I won't have to regrease them as often.

[eacmen]

Okay, I guess I'll keep my eye on pad wear and bushing OD wear against the caliper itself. As long as the pads wear straight and the bushing movement in the caliper doesn't affect it, I'll be happy.

Yeah I bought longer ones from Condor Speed Shop because they're about the same length as the stock ones. They provide a rubber cap so in theory I won't have to regrease them as often.

That dust cap feature is nice. Now I have buyers remorse.

Watched their video. Looks like they have the same amount of play in the caliper they used to shoot the video. I honestly don't think it's anything to worry about.

Even though they have the dust cap I would still watch the grease on those pins though. If they seize up it could be very dangerous.


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[Tbonem3]

Don't forget to lube the brass guides with hi-temp lube like permatex ceramic!

[timmo]

Don't forget to lube the brass guides with hi-temp lube like permatex ceramic!

Good point, I put syl-glide in there but the temp ratings aren't high enough. Gonna have to go back and re-lube it before hitting the track again. Should be fine for street/autox for now though

[r4dr]

Got my brass bushings in, but have a question.

How much play was there between the bushing and the caliper? You can easily slide the bushing back and forth axially between the shoulder and the circlip, as there is an extra 3-4 mm in length than the caliper itself (seen in pic below). Seems like that fitment is looser than the bushing to the pin itself, so I would think the caliper would slide on the bushing before the pin on the bushing.

Also interestingly enough, I did 1 more trackday with the pads swapped left/right and the taper is now gone, both sides are more or less worn even.

That's normal. Mine move in and out of the caliper body at least a couple mm. The part that moves with brake pedal pressure would be the pin inside the bushing. Mine don't have caps (I have a feeling they would melt on after track days) but that play is normal.

I tend to swap my pads from the inside to the outside when I go to grease my pins. The outers seem to wear faster which makes sense since the inners get more of the brake ducts' air flow. I also seem to crack the outer rotor face instead of the inner.

[r4dr]

That dust cap feature is nice. Now I have buyers remorse.

Watched their video. Looks like they have the same amount of play in the caliper they used to shoot the video. I honestly don't think it's anything to worry about.

Even though they have the dust cap I would still watch the grease on those pins though. If they seize up it could be very dangerous.

IIRC you have a track car, I wouldn't bother with dust caps. I'm not sure I would run brass bushings at all on a street car for those reasons -- the rubber boot is supposed to be a grease-free solution according to BMW which strikes me as better for the street.

[timmo]

I tend to swap my pads from the inside to the outside when I go to grease my pins. The outers seem to wear faster which makes sense since the inners get more of the brake ducts' air flow. I also seem to crack the outer rotor face instead of the inner.

How do you do that with the clip for the inner pad, do you drill out the rivet(?) that holds it on?

[eacmen]

How do you do that with the clip for the inner pad, do you drill out the rivet(?) that holds it on?

The PFCs and Pagids we run don't have the clip. Just cut it off. I think DTCs have the clip, nothing a cutoff wheel and file can't fix.


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