Retract the pistons as far as you can (I use a large flat bladed screwdriver between the old pads), then while applying pressure against the pistons loosen the lever bleed port screw just until you burp a little fluid out. Retighten the lever screw, wipe or wash off the spilled fluid, and install the new pads. As long as you keep the system pressurized, air shouldn't leak in.

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^^^ yep. I found it pretty common that people add fluid or bleed the brakes with worn pads, then there's too much fluid to fully retract the pistons when installing new pads. Cracking the bleed screw while pushing the pistons apart does the trick.

Here's how I force the pistons back. I leave the pads in the caliper and take two flat bladed screw drivers I just thoroughly cleaned with alcohol then push them in between the pads from opposite sides of the caliper. It nicely does the trick without cocking the pistons or possibly chipping/breaking ceramic pistons.

 

Should I be squeezing from the piston side or the lever handle? rear brakes would be harder to manipulate this way. Front could be OK. brake lever is nice because the control and operation is all there in one shot.

 

Piston side. It's a reach for the rear, but if you turn the handlebars you should be able to reach both ends at once.

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No fluid came out. Are they mate N lok connections, with the fancy bleed kits?

 

Method 1:

mount bike in stand

remove front wheel

Rotate the handle bar/loosen the brake clamp and rotate the reservoir so its level.

crack open the bleed screw on the brake reservoir so that it can leak. (Just about totally removed)

place the two cleaned flat blade screw drivers between the pads. One from the top and One from the bottom.

push the screw drivers in a little bit.

this should force the fluid out.

if you squeeze the lever, it will close the system off and no fluid can escape from below the lever piston. If it did, you wouldnt build brake pressure to stop with.

dot fluid will ruin the paint on anything it touches. Once you remove some fluid. Tighten up the bleed screw and then wash the whole lever assembly with soapy water.

Or... you could do the reverse, which i prefer.

Method 2:
Turn the bike upside down

remove wheel

remove pads

Crack open the bleed port on the calliper. (Dont worry. It must be turned once loose to actually leak fluid)

leave the allen key in the hole With a paper towel around it.

Very gently squeeze lever to remove a bit of fluid. open the calliper bleed a bit more if fluid doesnt come out. you might see a little air come out!

*do not release the lever, but actually tighten the bleed port while squeezing. (So you dont suck in air when releasing the lever)

When done, wash everything w soapy water.

 

That worked a treat. Thanks!