I'm getting ready to chase an air bubble out of my front brake system. As always, there are lots of opinions on the best way to bleed brakes. Some suggest pulling the calipers and wedging the pads so that the pistons are retracted and all the fluid is pushed back into the system for draining. Do you think this is necessary?
Thanks and take good care.
Is it necessary to REMOVE the calipers then wedge the brake pads back?-- NO.
Is it a good idea to pry the brake pads/pistons back into the calipers & shim there before bleeding -- Yes.
Prying the caliper pistons back into the bores does decrease the volume behind the pistons & help the bleeding process but not really
necessary if the brakes are bled regularly on schedule.
The main requirement of prying the brake caliper pistons back into the bores then PROPERLY shimming there (proper shim thickness) is for
the final stage of refilling the fluid reservoir. If the pads are worn & you don't shim the pistons to the correct location you can easily overfill the
fluid reservoir so next tire change when you pry the brake pads back to remove the wheel it can cause problems.
If you do pry the brake pads back before bleeding then use care-- if someone bled the brakes last time without prying the pads back & properly
shimming then you could have too much fluid in the reservoir & have it overflow with force when you remove the reservoir cover. (brake fluid will ruin painted surfaces & dash plastic)