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Discussion Starter #1
Does this caliper look used-up?
I'm concerned about that circle with the cross-hatched pattern at the bottom of the cylinder.


Edited by - dmkinsey on Jan 13 2008 8:47:15PM

Edited by - dmkinsey on Jan 13 2008 8:49:03 PM

Edited by - dmkinsey on Jan 13 2008 8:58:29 PM

Edited by - dmkinsey on Jan 26 2008 10:23:48 PM
 

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looks like part of the casting to me. With calipers the two critical areas are the bore and the piston, so long as they are corrosion free, not pitted or scored, they should work. Next in line is the passages which can be blocked by crystallized brake fluid.

what caliper is it? For what bike? Obviously information is not your strong suit....
 

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Discussion Starter #3
Sorry,
It's for my '86 Honda 700. This bike has a dual rotor front with a drum rear. The fronts are dual piston calipers.
I think one of the pistons on this caliper was stuck. I used compressed air to get it out of the caliper and the fluid behind the piston looked like snot. The piston has some marks on it and some pitting so I'm going to replace them both. I suspect that the other caliper will probably be the same.
The cylinder walls look good.
I think all these parts are original equipment. The guy I bought it from kept a log of everything he did to it and there's no mention of brake work. Besides being twenty years old this rig also has 30,000 miles.
My current theory is that there's a liner in the cylinder. That would make sense in terms of manufacturing. I think the metal at the bottom of the cylinder has disintegrated and the "stuff" is some adhesive. It's not building my confidence in this caliper.

Thanks for taking a look at the picture.




Edited by - dmkinsey on Jan 14 2008 12:32:21 PM

Edited by - dmkinsey on Jan 14 2008 4:19:04 PM
 

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almost all aluminum calipers have a steel liner, otherwise rust would not be as big an issue. The fluid you pulled out sounds like it just had water in it and had begun to dry out which is not uncommon (when it has water in it it get murky when it begins to dry out it crystallizes becoming like molasses before becoming crystals).

If that circle at the bottom is hard metal then it is casting. I don't know where you get this idea about disintegrating metal in a caliper they just don't work that way. One hole pushes fluid in, the piston slides in the cylinder. When the pressure is released one hole lets the fluid out and the piston retracts. There really isn't anything going on behind the piston besides fluid pushing it out and then itself getting pushed back into the MC.

for the record brakes should be services every 2 years. If not there is potential for fluid to go bad and ruin the inside of the caliper.
 

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Discussion Starter #5
I took it to the dealer and the service guy said "Yeah, that's OK. There was some water in the fluid."
 
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