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Check the thickness of the front pads. If they are very worn, the pads will contact the anti-rattle springs before the rotors. This is especially true if the rotors have ever been turned.
 

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With my 82 Spider on our 25 degree sloped driveway, I can almost stop it from still rolling down, but not quite, no matter how hard I press on the pedal. The pedal doesn’t hit the floor. At normal street speed, she stops ok....but I could never come to a skidding stop. Is this normal for a Spider?
Fresh brake fluid flush, new calipers, solid pedal, I believe it is well bled. The vacuum line to the booster gives a good swoosh when pulled off, so I think that’s good,right? Master cylinder problem perhaps?
My first action would be to examine the front pads: their thickness at several points at the edges of the material. Check runout of the rotors and thickness. Pull the pads out and clean the runners: the area where the pad backing slides toward the rotor. Something could be jamming the pad travel or the pad is not parallel to the rotor.
Also you may consider new pads and proper brake-in of the pads.
 

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With my 82 Spider on our 25 degree sloped driveway, I can almost stop it from still rolling down, but not quite, no matter how hard I press on the pedal. The pedal doesn’t hit the floor. At normal street speed, she stops ok....but I could never come to a skidding stop. Is this normal for a Spider?
Fresh brake fluid flush, new calipers, solid pedal, I believe it is well bled. The vacuum line to the booster gives a good swoosh when pulled off, so I think that’s good,right? Master cylinder problem perhaps?
The brake pads have been overheated, glazed from riding the pedal, not broken - in properly, etc. The booster/master should have nothing to do with this issue unless the booster isn't working or it's leaking.
The coefficient of friction of the pads has been compromised due to one (or more) of the above mentioned issues. Now the pad surface is hard and slick and they don't grip worth a ****. Get new pads, buy quality, and BREAK THEM IN PROPERLY. It is recommended to buy new rotors if you want to do it right. Otherwise you can cut a swirl finish on the existing rotors, or leave them alone (different schools of thought recommend different solutions regarding rotor finish). You'll be amazed at the difference. You can find adequate break-in procedures at your mechanic and search for how to break in brake pads. More break-in procedures can be found in the install instructions on some good pads, or online. It requires building heat into the pads in a measured fashion, so the pads "set up " properly. FYI-you can't rejuvenate a set of glazed pads, you will need to replace them.

Bob Volpe
 

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The brake pads have been overheated, glazed from riding the pedal, not broken - in properly, etc. The booster/master should have nothing to do with this issue unless the booster isn't working or it's leaking.
The coefficient of friction of the pads has been compromised due to one (or more) of the above mentioned issues. Now the pad surface is hard and slick and they don't grip worth a ****. Get new pads, buy quality, and BREAK THEM IN PROPERLY. It is recommended to buy new rotors if you want to do it right. Otherwise you can cut a swirl finish on the existing rotors, or leave them alone (different schools of thought recommend different solutions regarding rotor finish). You'll be amazed at the difference. You can find adequate break-in procedures at your mechanic and search for how to break in brake pads. More break-in procedures can be found in the install instructions on some good pads, or online. It requires building heat into the pads in a measured fashion, so the pads "set up " properly. FYI-you can't rejuvenate a set of glazed pads, you will need to replace them.

Bob Volpe
Traditionally called “ green fading”.
However if the car stopping is acceptable while driving it could be a combination of things including glazed-over pads. Best to check everything
 

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Discussion Starter #25
Decided to relook at the calipers. Appears to be caused by a few things:
  • pads do seem glazed
  • each caliper had one of its two ports blocked in the piston chamber. What’s the odds of that! Compressed air blew it clear. New seals in place.
Now on to replacing the wheel bearings while I’m here. See Vin’s thread, Wheel Bearings For Dummies.
 

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Glazed pads, or even if the pads have been replaced by pieces of wood, the car should be able to hold itself stationary on an inclined driveway.

There is something wrong with the hydraulics
Pete
 

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Glazed pads, or even if the pads have been replaced by pieces of wood, the car should be able to hold itself stationary on an inclined driveway.

There is something wrong with the hydraulics
Pete
Agreed. If the brakes are THAT weak, 0% chance it's the pads.
 

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Discussion Starter #28
Did you not read about the one of the two ports being blocked?! I think that means i wasn’t getting full hydraulic flow...which this engineer would think is a good reason.
 

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Did you not read about the one of the two ports being blocked?! I think that means i wasn’t getting full hydraulic flow...which this engineer would think is a good reason.
Agree, but I was amazed at all the other posts about glazed, etc. pads ... what???

Sounds like you have found at least some of the issue :)
Pete
 

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Sorry, that's not the problem. If air pressure (100 psi) cleaned out the port, hydraulic pressure (1200 psi) was not blocked.
 

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Agree. Still a force on pads issue though ...

Pete
 

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No, I put on 12.19 vented disk on all four corners, with calipers off a 1998 Porsche boxster, four pot brembos
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No, I put on 12.19 vented disk on all four corners, with calipers off a 1998 Porsche boxster, four pot brembos View attachment 1613388 View attachment 1613389 View attachment 1613390
Not required Bianchi, but you are modifying your car.

As the poster works back through the hydraulic system if his car he will find the issue.

EDIT: If we were discussing a 1910 Model T's brakes not holding on an inclined driveway ... then there would be many variables, but not a relatively modern car with standard brakes that are good enough to enter a 24/12/6 hour race event with (after a change of pad compound).
Pete
 

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Discussion Starter #38 (Edited)
Sorry, that's not the problem. If air pressure (100 psi) cleaned out the port, hydraulic pressure (1200 psi) was not blocked.
Fair point. Still seemed odd that it “popped” when blown out. Maybe with one port open, most of the pressure went through that open port?? We’ll see.
 

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I predict the front is not working much or at all, and only your rear brakes are doing the work.
Could be air, or a bad master cylinder.
 

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I think you need to work out where that piece that was in the caliper came from. Is a brake hose breaking up internally, or has a master cylinder seal failed?

Pete
 
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