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Newbie question, 88 calipers by arstneio
Started on: 01-10-2014 11:16 PM
Replies: 7 (173 views)
Last post by: arstneio on 01-13-2014 11:43 PM
arstneio
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Report this Post01-10-2014 11:16 PM Click Here to See the Profile for arstneioSend a Private Message to arstneioEdit/Delete MessageReply w/QuoteDirect Link to This Post
Hey guys,

Purchased a set of remanufactured rear calipers for my 88GT. Just had a few quick questions about clamping the piston. I know they're often bad, and I'm expecting to have to go return and exchange at least one of them.

One of them came with the piston already retracted, does that mean I'm good to go? The other one the piston won't retract, but the actuator screw rotates when I compress the hand break lever; the Ogre's Cave says this means bad piston, so go exchange for a different one?

I also want to confirm that the clamp method is the best method of doing this. It's definitely straightforward and easy to understand; I'm just a bit confused by this line in the Ogre's Cave: "GM DOES NOT recommend the use of piston rotation to retract the piston into the caliper in the 84-87 Fiero. Only 88 model Fiero pistons should be retracted by rotating the piston."

Does that mean that 88 pistons shouldn't be clamped?
Thanks in advance.
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Report this Post01-11-2014 09:56 AM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
If one of them is retracted and will allow the pads to be installed and slide over the new rotor, then you are good to go for that one.

For compressing the other 88 caliper, I would remove the nut from the parking brake lever, remove the parking brake lever, then clamp the piston to push it in. The parking brake shaft should spin backwards as the piston is compressed. Sometimes I help it by turning the parking brake shaft with a wrench (it has a hex portion), then compress, turn, compress, turn, compress... until it is fully retracted.
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theogre
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Report this Post01-11-2014 04:09 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
88 can use pressure when the nut and lever are removed.
Problem is 88 cast iron piece blocks a normal C clamp.
If you try anything else then make sure pressure doesn't load the piston unevenly etc.

GM made a tool for 88 that turns and put pressure on the piston w/o removing nut and lever.
Pressure is needed to turn inner piston and not stripping piston holes on front.

Good piston needs very little force to retract.

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arstneio
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Report this Post01-13-2014 12:17 AM Click Here to See the Profile for arstneioSend a Private Message to arstneioEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks for the info guys, much appreciated.

Why can't I just turn the C Clamp around and do it the other way, so the screw end is going to the socket to the actuator screw side, padding the piston surface of the caliper with like some cardboard or wood?
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Report this Post01-13-2014 07:42 AM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
You can.
Or you can remove the bridge (2 bolts) and just put the caliper side in a vice so you can see the shaft spin.
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theogre
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Report this Post01-13-2014 10:58 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by arstneio:
Why can't I just turn the C Clamp around and do it the other way, so the screw end is going to the socket to the actuator screw side, padding the piston surface of the caliper with like some cardboard or wood?

You can if clamp screw clears body, etc.

Yes you can remove the cast part, called the Bridge, but some have problems after. Bridge bolts torque is 74 lbs. ft. (100 N-m).
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Report this Post01-13-2014 11:20 PM Click Here to See the Profile for solotwoSend a Private Message to solotwoEdit/Delete MessageReply w/QuoteDirect Link to This Post
I always use the tool and be sure to turn then in the correct rotation. One is counter clockwise and the other is clock wise. I think that info is in Ogres cave.
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arstneio
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Report this Post01-13-2014 11:43 PM Click Here to See the Profile for arstneioSend a Private Message to arstneioEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks for all the help. Exchanged the bad caliper, and the next one they sent over the piston is already retracted. Actuator screw rotates, so I guess I'm good to go. Didn't even need to worry about compressing them in the end; guess I got lucky.
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