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Discussion Starter #1
I replaced the deformed and expanded rubber diaphragm on my rear brake reservoir. The original diaphragm got so expanded and out of shape, it nearly took all the available space inside the reservoir. I sat it for a week now and the original rubber is still totally out of shape. Anyone else have this syndrome? Thanks.
 

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That sounds like contamination to me.The diaphragm should not grow like that unless it comes in contact with oil etc.
 

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Discussion Starter #3
I see. ok, I will keep eye on the new one to see if problem persists. Weird, the original rubber looks like something out of a gory movie. Thanks
 

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Moisture does this, and they (the rubbers) often return to original shape once cleaned and left to dry, if your's didn't do this I'd be asking what brake-fluid is in there ? Dot 5 could do this too.
 

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Discussion Starter #5
I've used everything from Motul RBF 600 to the 660 to Torque 700. All DOT4. The deforming actually started when I first got the bike. I wonder did the shop use the wrong stuff during their initial bleed, as the tech setting my bike up did not do a good job on the rear brake and used foil as a gasket for the MV Corse exhaust :^)
 

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I'm with Mitch .... contamination
Donsy moisture doesn't affect rubber.... think of your tires or rubber bands

:wink2:
 

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Donsy moisture doesn't affect rubber.... think of your tires or rubber bands
I hear you Noel, but since I don't know what kind of rubber is used in these things, and we know that the brakefluid absorbs water........ is it possible for that to get into the "rubber" too ?

But for what it's worth I agree on it being some sort of contamination, hence my question on the Dot5 fluid.
 

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Donsy;
I've never seen any brake system rubber parts distort.......
DOT 5 is garbage DOT 5.1 is compatible with DOT 4

Stick to DOT 4 .....

Some old rubber parts would swell when dipped in acetone .....but if you put them in the sun for a hour they'd
go back to original size with no ill effects

:wink2:
 
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