And while brake pressure is present, the internal piston can't rotate (adjust).
it only rachets tighter after all pressure is off the pad, allowing the internal piston to slip inside the main piston.
Right. Adjustment can't occur while the inner and outer pistons are locked together under pressure because the clutch is under too much force to slip. That's why the adjustment occurs when you RELEASE the brake pedal, not when you apply it.
And as for pulling the piston and pad away from the rotor... The return force for the whole assy piston comes from the relaxation of the main hydraulic seal around the piston, not anything inside the piston itself. I'm sure you know this already, but that relaxation of the main seal pulling the piston back is the same phenomenon utilized in pretty much all calipers for pulling the pistons back from the rotor, not just the Fiero style.
They're all different varieties on the same theme, but two things that run common among all of them:
1) The retraction force on the piston comes from the main seal, and 2) The clutch is unloaded upon pedal release and adjustment occurs.
The real reason that the pistons doesn't ratchet themselves tight is because the clutch isn't unloaded until the hydraulic pressure is gone and the piston has already retracted back from the rotor because of the the seal around the outside of the piston.
Picture this... Your brakes are WAAAAAAAY out of adjustment. You've got a half inch between the pad and the rotor. You hit your brakes and push the piston out a half inch. This also compresses the spring inside the piston a half inch. Then when you release the pedal and the hydraulic pressure goes to zero, the piston will retract a tiny bit because of the seal. But then the other majority of the play should be taken up by the adjustment mechanism. If it doesn't it's because the cone clutch didn't slip like it was supposed to, probably because the inner piston is glued into the outer piston with crustified brake fluid or rusty goo.
Originally posted by FTF Engineering: If it doesn't it's because the cone clutch didn't slip like it was supposed to, probably because the inner piston is glued into the outer piston with crustified brake fluid or rusty goo.
Debating if the E-brake will self adjust is pointless. I personally don't think it will, I use my e-brake every day and it works great. Is it really that hard just to use it? Your supposed to anyway. I find manuals e-brakes tend to work better than autos, I find autos rarely work as no one will use the parking brake, thay all think they are above it all with an auto and 'park', just lazy, no other excuse, lazy. Debate all you want, but mine will hold my car on ANY hill, and you can say "how it should self adjust" while your car rolls down a hill. Just leaving it gear is not always the way, I have personaly had a Fiero come out of gear and roll through a parking lot, nothing got hit, but came out after eating and my Fiero was not where I parked it, (This was long ago and didn't have my parking brake set) so it CAN happen.
Originally posted by sardonyx247: I guarantee useing your hands is easier than this. That takes too much time to crank down. hands = simple, dont over complicate things, just push it on, easy.
If you have hands. Many don't or have hands/arms problems.
quote
Originally posted by sardonyx247: Debating if the E-brake will self adjust is pointless. I personally don't think it will, I use my e-brake every day and it works great.
GM thanks you for believing that myth.
quote
Is it really that hard just to use it? Your supposed to anyway.
No, not hard. Yes supposed to for Parking but not to adjust the brakes.
Every car must meet FMVSS rules. FMVSS says automatic adjusting they mean exactly that and No help or effort from the driver including using P-brake Because DOT/NHTSA knows that Most Owners don't use them.
Many use Disk w/ P-brakes in the caliper, like Fiero, but only 80's GM cars get "owners fault for not using P-brake" should give people a clue is compete BS. (For reference: Front and Rear Drum service brakes adjustment)
You live Nevada your whole life? Many live/lived in rust belt states and Canada. From around October/November to Spring... Using Parking Brakes are often a Bad idea because even New cars can have water frozen P-brakes. Is Very common to cut a frozen cables in the winter. You better hope the rear brake self-adjust hardware is good and working. Current cable products are better but many won't trust them because other parts can still freeze w/ p-bake on.
[This message has been edited by theogre (edited 02-18-2015).]
Fierobsessed: "good" piston is what I had at time of picture. Yes, can be bad too or another minor version of piston but two bad ones are dangerous bad units. They cause pad dragging and warp a rotor.
FTF Engineering and Fierobsessed... Adjustment after pedal release... Actually... 1/4" or more out of adjustment is common after brake work. Including most work on the axle/hub needed caliper removal. Compare to Normal Total pad clearance is .010 to .015 inch or less.
Yes, Pitch of threads tries to spin out the piston when enough pressure from inner spring. But Waiting to adjust after the pedal is unloaded can/will cause the piston to blowout the back cover on the piston as image I posted above. Inner spring does not have enough free space to compress more then maybe 0.2". (Spring compressed use door spring tool about normal installed spring height. Part to left are the spring thrust bearing.)
CLICK FOR FULL SIZE
The external spring, spring between piston and caliper body, is likely part of job to prevent blowout the cover in normal operation. The piston doesn't have anything to keep the back cover in except pressure from soft sheet metal cover. Very easy to remove the cover w/ just pump pliers...
I have been told by other engineers that Angle of Cone Clutch will affect pressure needed to lock up the parts. Meaning here the inner piston can slip under Xpsi line pressure to close the pads but not near/at Xpsi to load the pads to stop the car. Big difference in PSI needed to close the pads vs stopping the car.
(For others, Another "cone clutch" are tapers bits/tools for Drill presses and Mill machines. The angle they use mean will stay locked w/o any pressure. Front Fiero BJ have tapers that takes most of suspension load. The nut main job is just to put pressure to keep taper in the hole.)
Ok, so we decided to take another one apart tonight, To get a deffinite answer.
Now I see how it should self adjust without useing the handle. But, it ALL comes down to seal and thread friction VS spring tension. If the seal friction is greater than the spring tension it will never self adjust, by useing the handle you are helping to overcome the seal friction, but if the seal is stuck useing the handle wont help either. Thus why if you use the method I posted is post #1 (the main point of this thread) it WILL free the seal as it WILL have to spin.
I would still use your brake handle as I wouldn't trust it to self adjust.
Originally posted by sardonyx247: Ok, so we decided to take another one apart tonight, 1. To get a deffinite answer.
Now I see how it should self adjust without useing the handle. But, it ALL comes down to seal and thread friction VS spring tension. If the seal friction is greater than the spring tension it will never self adjust, by useing the handle you are helping to overcome the seal friction, but if the seal is stuck useing the handle wont help either. Thus why if you use the method I posted is post #1 (the main point of this thread) it WILL free the seal as it WILL have to spin.
2. I would still use your brake handle as I wouldn't trust it to self adjust.
1. But you won't get that because you live in dry states. Dry enough to matter. "Wet" states area near the Ocean or Rust belt states, call because Heavy use for Road Salt in Winter, can have allot more rusting/corrosion in the Void space that's vented to atmosphere. Even worse when you have damage/missing yellow "plug" or dust boot w/ "updated" pistons that vented on side or people drive thru high water.
Freeing up the piston in dry areas can last a long time. Freeing up the same piston in Florida, Delmarva Peninsula, or rust belt states can have problem like bad units I have above. You can see some of the rust in my cave but bottom image is before adding text etc.... Bottom of void have enough crap buildup to repeatedly bind up the piston but the rust is all over the cone and most of side area between the cone and sealing area.
CLICK FOR FULL SIZE
CLICK FOR FULL SIZE
2. That's fine but blanket statement saying using P-brake will save most is wrong. GM has been pushing same for around 30 years but is still a Myth. Many can and will have problems after freeing up a piston even when using P-brake. Just forgetting for a couple weeks, months or two, or even stored car can have frozen the piston again.
[This message has been edited by theogre (edited 02-19-2015).]
1. But you won't get that because you live in dry states. Dry enough to matter. "Wet" states area near the Ocean or Rust belt states, call because Heavy use for Road Salt in Winter, can have allot more rusting/corrosion in the Void space that's vented to atmosphere. Even worse when you have damage/missing yellow "plug" or dust boot w/ "updated" pistons that vented on side or people drive thru high water.
Freeing up the piston in dry areas can last a long time. Freeing up the same piston in Florida, Delmarva Peninsula, or rust belt states can have problem like bad units I have above. You can see some of the rust in my cave but bottom image is before adding text etc.... Bottom of void have enough crap buildup to repeatedly bind up the piston but the rust is all over the cone and most of side area between the cone and sealing area.
CLICK FOR FULL SIZE
CLICK FOR FULL SIZE
2. That's fine but blanket statement saying using P-brake will save most is wrong. GM has been pushing same for around 30 years but is still a Myth. Many can and will have problems after freeing up a piston even when using P-brake. Just forgetting for a couple weeks, months or two, or even stored car can have frozen the piston again.
1. I did get the answer, I wanted to see if/how it would self adjust, I now see how it should. I was agreeing with you that it should, now you are just arguing with your self. BTW I grew up in a salt belt, so get over where I live.
2. I did not say that.
I really fail to see what point you are trying to make at this point?.?. You don't want people to use thier e brake? You keep coming up with reasons to not ever use it and you just want it to work with out useing it?
I came up with a way that people could at least try to free it up and you have shot down everything about it. The adjustment you have in the cave does the exact same thing, try to get the piston to spin, I just have a better way of doing it. but you are saying just even to try it is wrong?? so do you think people should try to free it up? or what to you say people should do when it doesn't work as designed?
BTW these are questions. I am trying to find out.
[This message has been edited by sardonyx247 (edited 02-19-2015).]
I for one have found you thread very helpful. I never knew to use a 13mm wrench to get the ebrake cable loose, I always fought with it for some time. I also did not know how to properly adjust the cable, now my e-brake works perfectly. Thanks for your insight.
Cool. It's not the easiest thing to picture, and I agree that even though it SHOULD adjust automatically without using the parking brake, the truth is that over the years it's proven not to be a robust fault tolerant design. So what worked fine when brand new clearly doesn't work as intended a bunch of years down the road.
So about your method to force the internal piston to spin... Couldn't you do the same thing without going through all the effort of dismounting and splitting the caliper by just using the parking brake screw to draw the piston back?
Take off the p-brake cable and lever and then put the lever back on a sixth towards "p-brake engaged" from where it started, tighten up the nut enough to make sure the screw isn't pulled into the caliper body and then rotate the arm back to "off". Keep doing that until the piston is screwed all the way back into the caliper body. The only tricky part would be pushing the inboard brake pad back along with the piston in order to keep the pins on the back of the pad engaged (so the whole piston can't spin). Then once the piston is all the way home, the next sixth of a turn would force the piston to rotate.
It's essentially the same thing you are doing but saving the trouble of dismounting and splitting the caliper. Who knows... With all the agitation, you might even find that the inner piston starts to turn before you even get the outer one all the way back. If you turn the screw and the piston doesn't pull back, you know the inner piston is turning. I'm not sure which would be more work in the end, but just another idea.
If you get energetic, it would be pretty easy to build an adapter to screw onto the back of the parking brake screw that you could use instead of the parking brake lever. I haven't looked at it that close, but something that would clear the parking brake stop so that you could turn it more than a sixth of a turn?
quote
Originally posted by sardonyx247:
I also see I keep getting negs daily now, and this is the only thread I am involved in. And I was trying to help here.
Originally posted by sardonyx247: 1. I did get the answer, I wanted to see if/how it would self adjust, I now see how it should. I was agreeing with you that it should, now you are just arguing with your self. BTW I grew up in a salt belt, so get over where I live.
2. I did not say that. I really fail to see what point you are trying to make at this point?.?. You don't want people to use thier e brake? You keep coming up with reasons to not ever use it and you just want it to work with out useing it?
I came up with a way that people could at least try to free it up and you have shot down everything about it. The adjustment you have in the cave does the exact same thing, try to get the piston to spin, I just have a better way of doing it. but you are saying just even to try it is wrong?? so do you think people should try to free it up? or what to you say people should do when it doesn't work as designed?
1. Wasn't sure what Q your trying to answer. The point is "Dead" parts in Nevada might not see same conditions as Constant wet salt moisture near the ocean etc. I have seen many parts so rotten you can't take apart dead units. Above images shows rust pitting etc... Others w/ damage/missing yellow plug have water and crap inside the void space. I don't need them apart to get they are major hosed.
Big problem is many have blown back covers and any method could fake you thinking they work ok. My dead pistons seemed to work ok doing brake work but still wreck the rotor. I even retract the piston use C-clamp but still warped another rotor. I was surprise how bad they were when I pulled them out of the calipers.
2. Yes they should use P-brake... Don't Trust the caliper for self-adjust? Yes that's fine. You whole point of this thread seem to be agreeing w/ GM etc to use the P-brake Myth.
People can try this, my cave and others but don't expect much. GM's own method said you can use theirs whenever you want. If that works then you need it every time you have low pedal. If your method works and use P-brake then got lucky before rust got to them. Once rust sets in to the piston and the "clutch" is damage then many will have problem until they replace the bad pistons.
Using any method and then using P-brake might help or not depending on where you live/drive, How much driving, etc. More confusing, Using P-brake might work and still have frozen pistons because people don't drive enough to make pad clearance problems. It can take weeks to months, even longer, to show problems.
Low pedal and P-brake issues can sneak up on you. Pull level this month takes 5 clicks, pull level 60-90 days or even months later could take only 6 clicks w/ a frozen piston. GM spec is 5-8 clicks... Do you count the clicks ever time? Most won't notice until P-brake are useless.
quote
Originally posted by sardonyx247: I also see I keep getting negs daily now, and this is the only thread I am involved in. And I was trying to help here.
Not me. Plus the Triangle pointer haven't moved at all.
Actualy The whole point of this thread was to break the seal free.
This is not a fix all, and it could not adjust after either,(in wich case the caliper was bad anyway) or it could start working after this and save having to get another caliper and continue to work. But I was posting how to break it free, it has to break free doing this, it has no choice.
I had a couple of Fieros now that just would not "adjust" per the cave/GM method, too stuck, after breaking the seal free as per post 1, they work fine now. The first time I tried the cave method I had to move my ebrake lever back and forth prob 75+ times to finally get it to work. screwdriver slips off all the time, have to make a shim, a real PITA, The way I found one stroke of the lever and no shim, works every time.
This is all just to break the seal free, the only thing I was try to show. Everyone else got into the debate of how the damn thing works.
oh and the triangle did move, but now it is back to even.
I have been posting in the electric parking brake thread about getting my new stock brakes to work .I just wanted to say that this thread is where I got a lot of helpful information .And now my brakes work like new .Have not tested them yet , car is off the road till spring but the parking brake works and they don't leak .One thing I find a little odd is this : I put the park brake on , rotors lock up .Park brake off , rotors still have a lot of drag but can be turned by hand .Step on and off brake pedal , drag disappears and rotors turn freely . Probably does not matter that this is the way they work and I would not notice this if I did not have the wheels off .It is force of habit for me to step on the brake when I start up a car .
Debating if the E-brake will self adjust is pointless. I personally don't think it will, I use my e-brake every day and it works great. Is it really that hard just to use it? Your supposed to anyway. I find manuals e-brakes tend to work better than autos, I find autos rarely work as no one will use the parking brake, thay all think they are above it all with an auto and 'park', just lazy, no other excuse, lazy. Debate all you want, but mine will hold my car on ANY hill, and you can say "how it should self adjust" while your car rolls down a hill. Just leaving it gear is not always the way, I have personaly had a Fiero come out of gear and roll through a parking lot, nothing got hit, but came out after eating and my Fiero was not where I parked it, (This was long ago and didn't have my parking brake set) so it CAN happen.
Using the ebrake daily helps keep all moving parts lose and lubricated. Like those seals you are talking about freeing up inside the piston as well as keeping all the cables and points that move working. Leave an ebrake set when you park a car up here for a single winter even can get you a set of locked up rear brakes. And I mean locked up so tight no amount of work is going to get it lose again. I had 3 cars just in the last few years that someone had left the ebrake on over the winter as they didn't use a car in the winter here in Maine, he drove his 4X4 pickup all winter. and his was the old type drum rear brakes.
Using the ebrake all the time is a good idea to keep all parts of the system working, but never use it when storing over the winter or you might end up with a frozen piston, cable, seal or anything else. I don't drive the Fiero in the winter, none I have ever had were ever driven by me after the snow fly's, we use so much salt and crap up here its hard for any vehicles to last 10 years before things underneath start rusting through.
Steve
------------------ Technology is great when it works, and one big pain in the ass when it doesn't
Detroit iron rules all the rest are just toys.
[This message has been edited by 84fiero123 (edited 12-17-2015).]
Originally posted by 84fiero123: Using the ebrake daily helps keep all moving parts lose and lubricated... Using the ebrake all the time is a good idea to keep all parts of the system working, but never use it when storing over the winter or you might end up with a frozen piston, cable, seal or anything else. I don't drive the Fiero in the winter, none I have ever had were ever driven by me after the snow fly's, we use so much salt and crap up here its hard for any vehicles to last 10 years before things underneath start rusting through.
Using any cars Pbrake in winter for any reason has cause frozen brakes. Not just Fiero and don't need to store for a long time. Fiero and some others have wheel cables w/ both ends open to weather. Drum brakes have the wheel end inside the drum.
Sometimes you get lucky w/ a hairdryer etc to release Pbrake cables. MANY have cut the cables to release them to drive and fix them in spring. New cable designs are better but can still freeze in winter. Worse if plastic cover over jacket is bad.
Cutting Fiero cables must not damage the lever, spring and bracket. True that spring etc return Pbake lever to caliper's stop but keep it there so self adjusting works. W/o them the screw could move when you push brake pedal and that could lock or drag the pads.
"Using the ebrake daily helps keep all moving parts lose and lubricated." Loose ok but Lubed? Not really. If not soak in Brake fluid, most parts operate dry or w/ a coat of brake grease. Fiero's piston clutch where piston meet is "dry" by design. A bit of Fluid, etc, can build up causing rust to freeze up even in summer. PB Cables are dry and "wrong" lube can kill them.
I live in MN and have had Fieros since 1989. About 12 years ago I tossed the rear calipers in the circular file and replaced them with front calipers. I drive my car year around and have never spun out - so do not tell me it will change the bias and make the car dangerous. The car still locks up the front first on ice or dry tar if I slam the brakes on. I know this is not the way Pontiac designed the car but all I can say is I have never once regretted this solution. And I do not miss messing with those crappy factory rear calipers and sticking cables. My rear brake pads last a LOOOOOOTTTT longer now too. NOTE - I have an automatic and would not advise this to owners of cars with manual transmissions. Also if you park on very steep hills often, you may want to spend the time and energy on keeping a parking brake.
I live in MN and have had Fieros since 1989. About 12 years ago I tossed the rear calipers in the circular file and replaced them with front calipers. I drive my car year around and have never spun out - so do not tell me it will change the bias and make the car dangerous. The car still locks up the front first on ice or dry tar if I slam the brakes on. I know this is not the way Pontiac designed the car but all I can say is I have never once regretted this solution. And I do not miss messing with those crappy factory rear calipers and sticking cables. My rear brake pads last a LOOOOOOTTTT longer now too. NOTE - I have an automatic and would not advise this to owners of cars with manual transmissions. Also if you park on very steep hills often, you may want to spend the time and energy on keeping a parking brake.
In states where a Parking bake is required for the states safety inspections anyway you would be braking the law.
Well, apart from the discussion about what (not) to do when these brakes do work this thread does show what to look for when you're rebuilding these. I did one several months ago and had it all apart before reassembling. It is good to know now how everything works! I knew about the adjusting stuff but not all about the stuff happening inside the piston. So kudos to everyone contributing to this thread.
Btw I did not replace the inner seal because the replacement was just a little too tall and the original was still ok
I was just going to redo this thread, titled "How to fix your e-brake" as adjust is not the right title, and most of the info got lost(forgotten) in the debate, and the negs I first got over the debate. Though the debate did bring up 'some' valid points. But my original first post was to fix/get working a non working e-brake. But it got bumped so this thread will continue. I added some edits to the first post in green
Did I use too many pics and people just skimmed over the content. I want input to be able to write better how to's.
[This message has been edited by sardonyx247 (edited 12-17-2015).]
My brain is hurting from reading all this jargon on e-brake adjusting principles. One things for sure though...,if you ever need a Fiero "poster child" for DRAGGING rear brakes, my 85 GT is it! Kit
I just pulled my little GT out of the mothballs and am getting it road-ready. It was sitting in storage for 8 years and I figured I should enjoy it now because I'm not getting any younger. Both rear brakes were locked up and right rear brake caliper had no fluid in it which I thought was rather odd. It turned out that the right-rear brake line was plugged at the junction where the line ran through the crimped-on mounting bracket. After destroying the line trying to get it unplugged, I decided to spring for new lines on all four corners and ordered a set from the Fierostore. I changed out the lines and flushed the entire brake system with new brake fluid and bled the system. The right-rear caliper, however, was still seized. I suspect the cause is a frozen piston but I won't know whether this is the case until this weekend when I have some time to disassemble the caliper.
I've been reading up the materials in the Ogre's Cave which I find extremely helpful and of course, this thread. Based on what I've read, my thinking, at this point, is to remove both of the rear calipers and brake pads and then pull on the e-brake lever bolts to see if the pistons spin. If they don't, then I know they are seized and need to be freed via the instruction sin the first post in this thread. Am I on the right track?
I understand that the rear pistons can go bad and that even rebuilt ones fail. What then is the solution for a "bad" piston? Can I rebuild them? If not, do I order a replacement caliper and keep my fingers crossed?
~F
------------------
Farknocker's Superfly Yellow '87 GT 355ci Chevy ....chicks dig it, men fear it.
[This message has been edited by Mr. Farknocker (edited 10-24-2018).]
After 8 years of sitting I would just get "new" calipers. I bought a Centric and Raybestos last year and both worked OK. I can see only a Centric right avail on RockAuto though so I'm guessing rebuild parts and cores are getting scarce.
This thread was great for me. I just reworked all my brakes, including emergency brake cables. I couldn't figure out how the rear pistons could move without rotating the emergency brake screw and lever. I finally just gave up and put it in the how electricity works box. I didn't know there was an over running clutch (that's what I am going to call it..leave me alone) inside the inner piston. Now it all makes sense. Thanks..
