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I've fitted 2 new ac delco calipers on my 84 Trans Am. Bled the system as I done a new master cylinder too.
and the rears are crap. The pads rattle around inside the calipers too. Do I need some sort of spacer ? Usually you get those little clip things for the front pads so thet locate properly. But I didn' get anything like that with these. They came with new pads too.
I've just got a feeling the rears are like this because there is too much of a gap between the caliper and the inner most brake pad ? So my foot is travelling quite a bit before the car starts slowing. And then it only gradually starts slowing. I want to be able to lock the wheels If I stamp on the brake
How are your rotors? Are they the correct thickness? Here also is a great read about the proportional valve spring upgrade. I have done the upgrade and it works great, but you also need good brakes before you do the upgrade. https://www.thirdgen.org/forums/brak...e-upgrade.html
How are your rotors? Are they the correct thickness? Here also is a great read about the proportional valve spring upgrade. I have done the upgrade and it works great, but you also need good brakes before you do the upgrade. https://www.thirdgen.org/forums/brak...e-upgrade.html
well that's something to think about. Yeah the rotors are good and have plenty of meat on them. New brake pipes to all 4 corners. New pads and calipers were done before I bought the car with new hoses. And I've just replaced the rear calipers and made the car worse lol.
should their be a little metal spacer thing between the caliper piston and pad because they are moving freely in the caliper
Hmmmm...they definitely weren't in the boxes. Looking at that though it seems to be exactly my problem as that will put a nice gap between the piston and pad ? Hopefully take up that pedal slack I've got. I just have to find some of those now.
the rear pads just sit in place. I tapped a flat piece of steel into the outer pads on both sides to sort of lock them in place
Need to use the parking brake to adjust the rear calipers. That and you may also need to bleed them better. Even the smallest amount of air will cause a low pedal.
Need to use the parking brake to adjust the rear calipers.
^^^ This ^^^
"ears" that have to be bent to fix the pad against the caliper body
^^^ And this ^^^
Even the smallest amount of air will cause a low pedal.
^^^ And this ^^^
All of those things, if not ABSOLUTELY PERFECT, will add up to the typical sloppy, noisy, ineffective brake system we all know and love so well.
Each time you pull the handle, the pistons adjust out some microscopic amount. Until you work the parking brake about a million times, there will be a gap.
Then, once you get them adjusted up, use the parking brake EVERY SINGLE TIME you park the car; and twice on Sundays. And if you ever notice the pedal getting low again, just sit in the car and pump the handle for a few minutes.
That system is SUCH CRAP even when it works right, which is RARE... I'd rather have drums.
All of those things, if not ABSOLUTELY PERFECT, will add up to the typical sloppy, noisy, ineffective brake system we all know and love so well.
Each time you pull the handle, the pistons adjust out some microscopic amount. Until you work the parking brake about a million times, there will be a gap.
Then, once you get them adjusted up, use the parking brake EVERY SINGLE TIME you park the car; and twice on Sundays. And if you ever notice the pedal getting low again, just sit in the car and pump the handle for a few minutes.
That system is SUCH CRAP even when it works right, which is RARE... I'd rather have drums.
well that' great then because I can' use the handbrake. I got a new LH cable which fits at the caliper and up the body but the actual cable is too long ! The RH side was replaced before I got the car and it's the right fit.
so you ratchet the handbrake and the piston adjusts better? I will get on that then.
I've got an 87 too which has drums at the back and it' absolutely fine. These disc rears really are ****! So I need to sort the handbrake. Get a set of these clip things that weren't with the calipers, bleed them again just incase then hopefully it works.
well that' great then because I can' use the handbrake. I got a new LH cable which fits at the caliper and up the body but the actual cable is too long ! The RH side was replaced before I got the car and it's the right fit.
so you ratchet the handbrake and the piston adjusts better? I will get on that then.
I've got an 87 too which has drums at the back and it' absolutely fine. These disc rears really are ****! So I need to sort the handbrake. Get a set of these clip things that weren't with the calipers, bleed them again just incase then hopefully it works.
To point out the issue, there's two different length cables for the parking brake. One for the drum rear, and one for the disk rear. You likely received the one for the drum rear.
To point out the issue, there's two different length cables for the parking brake. One for the drum rear, and one for the disk rear. You likely received the one for the drum rear.
I made sure I ordered the one for disc brakes from rock auto and it's the right part number on the box. It' definitely too long though.
it' so much hassle to return something thoigh because I'm in the UK
I'm pretty sure I've run across threads where people had the same issue; they ordered the correct part according to the vendor, but it was in fact the wrong length.
My recommendation would be to measure the length of the one you have now, and then find a vendor that lists the length of the cable and pick the shorter of the two (assuming its shorter than the one you have now).
To throw another wrench in the works, I think the better PBR\Aluminum caliper rear brakes might have a different cable also. That should only show up on newer models though if you're searching by vehicle. I think 89+?
I'm pretty sure I've run across threads where people had the same issue; they ordered the correct part according to the vendor, but it was in fact the wrong length.
My recommendation would be to measure the length of the one you have now, and then find a vendor that lists the length of the cable and pick the shorter of the two (assuming its shorter than the one you have now).
To throw another wrench in the works, I think the better PBR\Aluminum caliper rear brakes might have a different cable also. That should only show up on newer models though if you're searching by vehicle. I think 89+?
no wrench here. I ordered ac delco calipers and an ac delco cable from rock auto. Im Not sure where you get the pbr calipers from
There's two different versions of rear disk brakes. One type, later model cars, is aluminum (PBR), one type is iron (Delco-Moraine). They may use different length cables.
There are a bunch of E-brake cables. Two different lengths for the later cars, but at least the right and left are the same cable.
On the earlier disc cars, the left and right cables are different from each other because of the staggered calipers and the routing. I surely wouldn't put much faith in what the parts computer lists for the cables. Not when there are GM catalogs from "the day" that are often more specific and accurate. Physically matching the old cable to a new replacement is a reasonable substitute.
Here's the chart from The Good Book (Link- https://drive.google.com/folderview?...Wc&usp=sharing ). Keep in mind most of the numbers have changed since 1991 when the book was printed, but you should be able to find the new numbers from the old numbers.
Even with all the right parts, ideal perfect world conditions, etc don't expect much from the pre-89 discs.
well that' great then because I can' use the handbrake. I got a new LH cable which fits at the caliper and up the body but the actual cable is too long ! The RH side was replaced before I got the car and it's the right fit.
What Brand Did You Use,I Used These On My Car And They Fit Just Like OEM,These Are Also Shown To Fit Your Car.
Its an AC Delco cable, the #18033314 one you mentioned. its 63.5 inches long. The Wagner one is the same length and the Dorman cable doesnt have its length on it.
Heres the cable fitted, ignore the zip ties on it.
Ive took the new handbrake cable off the car, and here it is laid side to side with the old one. the old cable is the one with the two round things on, and is ever so slightly shorter. however you can see the metal mounting points are in different places
The old cable loops out further behind the axle before going back up and under the car. the only reason this cable had to come off is because it had a weird nut thing on where it should click through and secure to the caliper, but it wouldnt lock in place at all so when you pull the handbrake the cable just flopped around and was still slack.
So then........WTF now. ive got no idea which cable to order because they are all listed as 62 inches
I struggled with my rear disc brakes this last summer. All New AC Delco parts from Rock Auto, everything, but couldn't make them work at all. Ended up adjusting them as Chilton and Haynes manual says, thightening the ebrake adjuster until pads barely contacted the rotor. If I then loosened as much as manuals stated, I lost all rear brake effect. So I let them be where they almost rubbed, and operated the e-brake lever x times ever since to keep it alive. What a difference from the crappy brakes I had.
For the loose pads, I had a hard time bending the ears around the caliper. I have redone it two or three times later, and now it is time again. I hear clunking at low speeds which goes away at the smallest brake pedal touch.
Another thing to help, there's a relatively easy modification you can do as long as you have the aluminum prop valve. You can change the spring to add more pressure to the rear lines. Haven't done this myself, but I probably will.
Not too sure about the spring mod. As I understand it, the spring mod originated with experimentation on a late PBR equipped car. From there, it was applied in a haphazard manner to any other rear brake system, with nothing more precise than "feels soooo much better". Placebo effect is a powerful thing.
Further, in reading about the PBR/1LE rear discs, GM altered the brake bias after a few years of 1LE development. Later 1LE cars have less rear, and more front bias. Reportedly the engineers felt that too much rear brake bias created a tendency for the rear brakes locking up dangerously. Think about that a bit before randomly applying a very unscientific mod thread.
One clear indicator of the quality of that thread, is the varying views on the "upgrade" spring. Notice several users quote the spring rate, while others are quoting the maximum load. These are very different things.
Finally, to sum it all up, the problem with Delco-Moraine rear calipers, and the perceived brake bias issue of 89-up PBR calipers are two different issues. The issue with DM calipers is a mechanical and functional issue based in poor design and unrealistic maintenance requirements. The issue with PBR calipers is based in only brake bias, erroring on the side of safety.
The front/rear bias, and fluid volume requirements of the DM calipers, and that of the PBR rears are completely different. DM cars use a different master cylinder, and different prop valve. The calipers use different size pistons, and they use different size rotors. The concept that the same spring upgrade would result in the same improvement for both styles of rear discs, just doesn't jive. Are people who do the swap actually resolving an issue? Or are they just masking it under placebo effect and greater rear bias?
Are people who do the swap actually resolving an issue? Or are they just masking it under placebo effect and greater rear bias?
As one whom has done the spring swap on a stock '86 IROC. I can attest to the fact that stock with the rear wheels lifted off the the ground car in drive idling, rear brakes would not hold the wheels and they just spun, with the 19lb spring swap, rears hold even with a load.. Braking has much improved. As far as detailed bias facts and history of the swap, I have no clue.. Just found that thread years ago after fighting with rear DM's for years, and it has solved my issues with them, as long as you keep them adjusted, it works well for my particular situation..
But see, that's the problem. People see a suggestion, don't really understand why they should or should not do the mod. People recommend a mod they don't fully understand. Understand why that is a problem?
If you need I can double check but I should still have a good cable in the garage you can have. I am finishing up with my brake upgrade and will not need it. What part of England are you in. I am at ip27 9ga.
If you need I can double check but I should still have a good cable in the garage you can have. I am finishing up with my brake upgrade and will not need it. What part of England are you in. I am at ip27 9ga.
thats very kind of you mate. Im in Newcastle. If you think the cable is the right one then that would be awesome. I will PayPal the postage for it just let me know
But see, that's the problem. People see a suggestion, don't really understand why they should or should not do the mod. People recommend a mod they don't fully understand. Understand why that is a problem?
Don't get me wrong, I understand what you're getting at, and I appreciate that you're advocating for safety. That being said, I'd like to give people the benefit of the doubt and say that if they change the spring they understand what they're doing at least on a fundamental level. We don't all have access to line pressure testing equipment and the like, but we can swap a spring and do some real world testing. It can also be dangerous to be stopped at a sign or light and have your rear wheels still spinning.
As far as the spring masking the issue... It's certainly possible. But, I (foolishly) installed brand new calipers, brand new rotors, brand new Stillen pads, and brand new lines. I have pulled the parking brake literally over a thousand times trying to get them to adjust further, and with the car in gear, I cannot stop the rear tires from spinning unless I push with all of my might with both feet, using the seat and steering wheel for leverage. With all of that being said, my car hasn't seen any street time yet as I've completely rebuilt the car and still have a little work to do.
Will the spring fix it? I don't know. I'm going to test the car as is first, and then try different springs to find out what works. It's a fairly easy change and a bit cheaper than an aftermarket proportioning valve (especially since I've invested so much in these junky things already). Of course, this is all assuming that I don't stumble across a brake upgrade kit that I happen to have cash for when I see it. I'd drop these brakes like a bag of flaming turds given the opportunity.
gta_knight, I apologize for cluttering up your thread.
Thanks to all for the info in this thread, very informative. My recently acquired '87 has poor braking and I bet the rears are the blame since I know it to have recently had 4 calipers.
Drew, are you in engineering? If not I think you should be. I heartily endorse understanding how a system works and not just a component or two and also discovering the difference between treating symptoms and root causes. I think your warnings on the spring mod are justified. That said, with careful consideration and testing, it could be a good way to improve braking if it was undersized from OEM. Hopefully those who mod this are aware.
That Cable Doesn't Look Correct,No Need For That Nut On There The End Should Look Like This It Should Just Snap Into The Cable Bracket.
yeah thats the old one that was on the car when i bought it, i dont know why someone has done this but they have basically ruined the cable as it wont secure into place ! and the new one is too long......aaaaargh
retaining clips turned up, i clipped it around the piston on the caliper like in the picture but im not sure which way round it goes and where its supposed to sit against the pad ? the few times i tried to locat the pad the retaining clip just kept popping off the piston.
Ok. Got all the brakes back together and tightened the handbrake cables, couldn't move the discs with my hand....seemed fine. Put the car back on the ground and the handbrake does nothing... doesn' even hold the car slightly.
tightened the cables up even more, still nothing. Even though the handbrake lever in the car feels solid to pull up. The cables are pulling fine as the springs on the calipers are getting fully compressed. So why the hell do the pads not grip the discs?
I put the car in drive while it was on the stands and the foot brake is working fine and stopped the wheels. But the handbrake does nothing even when it's fully on super right ????
Did You Make Sure Your Caliper Lever's Were Against The Stops On The Caliper Housing.
dont think so. I slackened the equaliser nut back off again earlier and tried a method some other said by pressing and holding the brake pedal then pulling the handbrake and it worked a bit. The caliper is grabbing the disc now but it's weak as anything and I can still move it with my hand.
so these stops, Have you got a pic of them so I know exactly what I'm looking for
So ive been back at it today with no results. Adjusted the handbrake as per the book so the levers were against the stops on the calipers then i tightened them so they were just barely touching. the handbrake goes up 14 clicks, doesnt do anything at all.
Ive also got a big gap between my outer pad and rotor on the passenger side, it also rattles around a bit on the drivers side but the gap isnt as big
im wondering what thickness a new set of rotors are ?? i literally cant think of anything else other than theres too much slack causing the handbrake to not engage and also the excessive pedal travel too.
The nominal thickness of new rotors is around 26.3 mm. Replacement thickness is under 24.4 mm. So that one looks good to use at 25.0 mm.
RBob.
thanks man. After talking to a mechanic that does 3rd gens he says I need to manually wind the piston out of the caliper off the car. That gets rid of all the slack I have. Just so the pads are tight to fit in place then adjust as normal once on the car.
so........i need to remove the calipers from the car again to do it. Damnit. And he uses a specs tool for hooking on the piston to turn them but I cant seem to find one on eBay.
awesome man, its easier when you know what to actually look for! lol, once I typed in caliper cube loads of them came up. got one ordered so hopefully I can wrap these damn brakes up next week finally
01-14-2018, 10:15 AM
