rear disc brake adjustment question
#1
rear disc brake adjustment question
Ive seen this answered both ways. On my 86 Iroc, do the rear brakes automatically adjust without using the parking brake. The piston screws in and out of the calipers on this model year up till 1988. By pressing on the foot brake, does the pressure cause the pistion to rotate out causing the pads to clamp the rotor? Do hydrolic pressure alone cause the piston to turn counter clockwise to apply the pads?? it does not make sense to me because the piston screws in and out rather than a smooth bore like must modern brakes
Others have told me you MUST use the parking brake to keep the pads adjustested close to the rotor? Im not talking about the parking brake holding the car still, Im talking about taking up the slack as the pads wear down just like a non screw in piston.
Thanks, Tommy
Others have told me you MUST use the parking brake to keep the pads adjustested close to the rotor? Im not talking about the parking brake holding the car still, Im talking about taking up the slack as the pads wear down just like a non screw in piston.
Thanks, Tommy
#4
Moderator
iTrader: (5)
Re: rear disc brake adjustment question
Here's a thread with info and links that may provide the info you require:
https://www.thirdgen.org/forums/brak...ke-adjust.html
Good luck with your project,
JamesC
https://www.thirdgen.org/forums/brak...ke-adjust.html
Good luck with your project,
JamesC
#7
Senior Member
Join Date: Nov 2001
Location: Erlanger, KY
Posts: 915
Likes: 0
Received 2 Likes
on
2 Posts
Car: 1989 Iroc-z
Engine: 350 TPI
Transmission: Auto 700R4
Axle/Gears: 9 bolt - 2.77
Re: rear disc brake adjustment question
My 89 iroc is an early build(9/88) and it has the self adjusting pbr calipers on the rear.
Trending Topics
#8
Re: rear disc brake adjustment question
member 841le said in that refering link: Should'nt have to if you've got new calipers.Especially if the pads are new too.
I never used that method.I would leave the E-brk lever on the back of the caliper off.Then just pump the brake til the pads re-seated.
I never used that method.I would leave the E-brk lever on the back of the caliper off.Then just pump the brake til the pads re-seated.
#9
Member
iTrader: (3)
Join Date: Apr 2006
Location: Lorain, OH
Posts: 134
Likes: 0
Received 0 Likes
on
0 Posts
Car: 87 Iroc
Engine: 350
Transmission: 700r4
Axle/Gears: 3:27
Re: rear disc brake adjustment question
I got a question about this adjusting procedure found through the link provided above....
What's the point of using the washer (spacer) and then tightening the nut down on your wrench? Why can't you just turn the shaft with your wrench until the pads are where you want them to be? My calipers won't "self adjust" using the parking brake, so I have to manually adjust them.
Q: Do my rear disc brakes need to be adjusted?
A: A technical service bulletin described this for early-mid '80s rear disk brakes. It seems that the rear disks in these cars would be adjusted by applying the emergency brake. When you pull the emergency brake lever up, the lever turns this little device called an actuator screw. This little screw type device is also on a ratchet, so that pulling the e-brake up, turns the screw. But letting go allows the ratchet part to function and set the pads at that time. So, using the emergency brake is mandatory for maintaining the rear disk setting on early model rear disk units.
But, here's the problem with them. There's a little spring on the actuator screw assembly that allows the pads to back-off from the disk a little bit before the ratchet mechanism is engaged. This must be done, otherwise full brake pressure would be left on the pads when the e-brake is released. Well, that little return spring K-factor was not correctly chosen from the factory, and the result is that the ratchet NEVER functions after the actuator screw gets a little dirty. Hence, the pads simply work their way out all the way when the e-brake is used. Using the e-brake all the time seems to keep the actuator free for a longer period of time, but even with the correct spring weight and screw, the e-brake is required to adjust the parking brake actuator.
The TSB states that cars with a manual tranny are eligible for a free fix as the e-brake is required to park the car, but the auto is not eligible. Why? Only GM knows. However, fixing it yourself should be relatively easy. The rear wheels are removed, and there is a nut on the back side of the brake caliper that holds the parking brake lever. Remove the nut, lever, and soft grommets. Put a large washer over the shaft to act as a spacer, and then put a wrench on the hex of the shaft, and tie it down with the nut. Turn the wrench to back the brakes off. After a while, this will over travel, as if there was a one way clutch. Tighten the shaft to see where the hex is when the pads are tight agains the rotor. If it is in a spot that the parking brake lever will fit, and turn about 1/3 of its travel to tighten apply the brake, then it is good. If not, try again.
This will remove some of the brake pedal slop also. It's supposed to be self-adjusting (apply parking brake thirty times), but it is common for it not to work.
A: A technical service bulletin described this for early-mid '80s rear disk brakes. It seems that the rear disks in these cars would be adjusted by applying the emergency brake. When you pull the emergency brake lever up, the lever turns this little device called an actuator screw. This little screw type device is also on a ratchet, so that pulling the e-brake up, turns the screw. But letting go allows the ratchet part to function and set the pads at that time. So, using the emergency brake is mandatory for maintaining the rear disk setting on early model rear disk units.
But, here's the problem with them. There's a little spring on the actuator screw assembly that allows the pads to back-off from the disk a little bit before the ratchet mechanism is engaged. This must be done, otherwise full brake pressure would be left on the pads when the e-brake is released. Well, that little return spring K-factor was not correctly chosen from the factory, and the result is that the ratchet NEVER functions after the actuator screw gets a little dirty. Hence, the pads simply work their way out all the way when the e-brake is used. Using the e-brake all the time seems to keep the actuator free for a longer period of time, but even with the correct spring weight and screw, the e-brake is required to adjust the parking brake actuator.
The TSB states that cars with a manual tranny are eligible for a free fix as the e-brake is required to park the car, but the auto is not eligible. Why? Only GM knows. However, fixing it yourself should be relatively easy. The rear wheels are removed, and there is a nut on the back side of the brake caliper that holds the parking brake lever. Remove the nut, lever, and soft grommets. Put a large washer over the shaft to act as a spacer, and then put a wrench on the hex of the shaft, and tie it down with the nut. Turn the wrench to back the brakes off. After a while, this will over travel, as if there was a one way clutch. Tighten the shaft to see where the hex is when the pads are tight agains the rotor. If it is in a spot that the parking brake lever will fit, and turn about 1/3 of its travel to tighten apply the brake, then it is good. If not, try again.
This will remove some of the brake pedal slop also. It's supposed to be self-adjusting (apply parking brake thirty times), but it is common for it not to work.
Thread
Thread Starter
Forum
Replies
Last Post
hectre13
Engine/Drivetrain/Suspension Parts for Sale
2
12-11-2023 08:14 AM
sailtexas186548
Engine/Drivetrain/Suspension Parts for Sale
8
01-19-2016 12:21 PM
novaderrik
Transmissions and Drivetrain
3
08-10-2015 12:44 PM
1992 Trans Am
Engine/Drivetrain/Suspension Parts for Sale
1
08-08-2015 08:16 PM