Reply to "silicone brake fluid after 20 years"

Things not so rosy in silicone fluid land after all:

I have disassembled all 4 rear calipers.

The two original ones were pretty healthy, although one piston in each was pretty stiff and probably not contributing to braking much.

All the pistons in the 'additonal" calipers were frozen to one degree or other. One outboard "direct" piston won't even move at all with hitting the piston from the inside with a hammer with the caliper in a vise , using a piece of pipe to avoid hitting the locking gizmo. I think that can safely be called frozen.



So I rebuilt the original calipers and all the pistons move with thumb pressure.



It seems to me that the "extra" calipers were just adding drag and no braking at all.

My take on it is that the original calipers were probably disassembed when the switch to silicone fluid was made while the "extra" ones were not. In fact, based on the circumferential corrosion in the bores, they may have been corroded when they were installed. Had they had glycol fluid in the dependent portions of the bores only that area would have rusted.


Jim