first caliper rebuild
72 with power brakes. The front calipers are off the car, the pistons, boots and o ring removed. I've cleaned the surfaces, blown dry, etc. My question has to do with how tight the new pistons with the ring seal ought to be upon installation. Mine are very tight and take alot of back and forth effort to bring them out. I am concerned about their retraction after braking and too much drag on the rotor. Will they loosen with use or do my s/s calipers need to be re sleeved?
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Re: first caliper rebuild
OK, what kind of "ring seal" are you referring to? The pistons generally when new will extend out to the limit of the dust seal, but should easily depress from that position. Have the calipers been sleeved?Bill Clupper #618 -
Re: first caliper rebuild
With the o ring on the piston, the assembly will not easily push down into the cylinder. It has not been re-sleeved recently. The walls of the cylinder are smooth and they are s/s. jimComment
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Re: first caliper rebuild
Like many others, I fail to see the need for the o-ring type seals. The tried and true OEM lip seals work great and don't exhibit the issue you're having.Comment
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Re: first caliper rebuild
A rebuild of calipers and master cylinder and cleaned lines with use of silicone DOT5 brake fluid can help extend the life of these components.Comment
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Re: first caliper rebuild
Oring configurations require a very close fit between the piston and the bore so althought the friction seems like a lot, it really isn't. I would not worry about it. Typical clearances for a 1" piston, plug= 0.998" bore= 1.000". Right out of the book. Lip seals have a much looser tolerance but are only designed for pressure in one direction. The fixed caliper works beautifully if there is no runout on the rotor but if there's big runout it can actually suck air inbecuase the rotor makes the piston oscillate back and forth. Orings don't care about the oscillation.Comment
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Re: first caliper rebuild
Did you lube the bores with fresh brake fluid before installing the pistons?
Unless the sleeves are new and/or were bored undersize, I wouldn't worry about it. Checking the bores with a dial or digital caliper and comparing to standard may help to ease your concern.
Disc brake pads do not ever fully retract from rotor contact.Comment
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Re: first caliper rebuild
You may be getting a little crooked in there when you push them in..like stated before there really isn't much room in there for wobble..whenever I do a caliper rebuild I use shop air to move it out and my fingers to push it in..that squares it up and makes sure it doesnt leak and the lip isnt rolled..of course we are talking about metered air and not full 140 psi shop air..just to keep those coments about flying saucers at bay..I haven't done o ring style as I have everything at hand to keep the rotors true..and I flush out the fluid alot..not sure other than that as to why they are to tight..and I am not talking about brake fluid..unless you didn't use any to install the pistons in the bore which..is kinda needed..Comment
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Re: first caliper rebuild
The o ring and the groove it sits in, and the walls of the bore were coated with dot 3 before installation. I will check the run out next. thanks jimComment
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