I recently had a leaking caliper and decided to order a rebuilt caliper from TFS. It arrived and it looks great. It is the unpainted one in the photo. The piston is original, as they are apparently not available anymore.

In the meantime, a local caliper rebuild shop told me that he can rebuild 88 calipers (seemed confident and says he is aware of the differences between 84-87 Fiero calipers and the 88 ones) and he says the pistons are the same. I realize that they are officially slightly different and were a different part number

I have installed one of his rebuilt calipers in my car and so far so good. No leaks and it seems to be working fine.

Just wondering if anyone agrees or disagrees with his assessment that the pistons from earlier Fieros would work fine. The face on his pistons is clearly different (the red painted one in the picture)

I have only driven the car once since the install and it is now stored for the winter, but it seemed to work fine and so far has not leaked. Does anyone recognize the piston on the red one?


thoughts?

[This message has been edited by cam-a-lot (edited 11-17-2019).]

[This message has been edited by FX (edited 11-18-2019).]

"Red" is "New Type" piston w/ notches for stamped SS pad clip for 84-87 Fiero and likely others.

CLICK FOR FULL SIZE

84-87 Fiero rear piston Is Not same total diam as 88. Only same in the guts for E-brake function.

Piston Size: 47.75mm (1.88") 88 Front and Rear
Piston Size: 47.57mm (1.87") 84-87 Rear
Piston Size: 49.05mm (1.93") 84-87 Front
From Cardone.com
88 MC size: 24mm (0.9448818898") per ACDelco

(Note that these numbers can change a bit in different "books" used. I have older rear listed as 45 then "updated" to 48mm on one page in my cave because of catalog data. Some cat's are just errors, others round up to whole numbers. If you follow rounding rules, both are 48mm but isn't for people designing or working on them.)

May seem to work and Yes, Seems very small dif but 88 shell w/ 84-87 piston can have seal leaks etc because of total size diff.
GM et al make the main piston seal to fit a specified bore AND the piston in that bore. Tiny piston size change makes the seal compress more or less. Less here old piston w/ 88 seal. Tight/loose seal can effect piston self adjust etc.
Plus will make rear brakes weaker because of hydraulic rules but you might not tell for normal driving.

Lower Performance? How bad? See my Cave, Brake Upgrade DL excel sheet and adjust to used 88 MC size and both pistons.
Unprotect the sheet then just enter diam and sheet should do the rest.
I get...

code:

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Setup             	MC mm	MC area	Cal mm	Cal area 	Ratio	Change vs Stock
Rear						
OE MC & caliper    	24	452.389	47.75	1790.757	3.958	0.000
OE MC & Old piston	24	452.389	47.57	1777.281	3.929	-0.030

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At the very minimum... If you run older piston you need to run them on both sides on rear axle or likely have brake steering problems, one wheel locking more/easier, etc.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

[This message has been edited by theogre (edited 11-18-2019).]