While reviewing the front brake fluid change procedure on the BMW DVD, I noticed that it specified removing the brake calipers and pads and using a special (probably expensive) pad reset tool to push in the brake pistons before changing the fluid. Is it really necessary to do this? Removal of the brake caliper and pads seems rather excessive for simply changing the brake fluid, as other bikes I've worked on only required opening up the bleed valve on the caliper and using the brake handle to pump in new brake fluid (with a little help from a Mighty Vac).
-
Welcome, Guest! We hope you enjoy the excellent technical knowledge, event information and discussions that the BMW MOA forum provides. Some forum content will be hidden from you if you remain logged out. If you want to view all content, please click the 'Log in' button above and enter your BMW MOA username and password. If you are not an MOA member, why not take the time to join the club, so you can enjoy posting on the forum, the BMW Owners News magazine, and all of the discounts and benefits the BMW MOA offers?
-
Beginning April 1st, and running through April 30th, there is a new 2024 BMW MOA Election discussion area within The Club section of the forum. Within this forum area is also a sticky post that provides the ground rules for participating in the Election forum area. Also, the candidates statements are provided. Please read before joining the conversation, because the rules are very specific to maintain civility.
The Election forum is here: Election Forum
2019 R1250RT: Question concerning Front Brake Fluid Change
- Thread starter rclark09
- Start date
pglaves
#13338
The described procedure is intended to make sure the caliper pistons are fully retracted so that no old fluid remains in the calipers. It has long been a good procedure to spread the pads fully to fully retract the pistons. I have done that, but have not always done that.
My preference would be to change the fluid more often and not worry about retracting the pistons.
lkraus
New member
I've made wood blocks out of scrap to press the pistons all the way in and keep them in place while flushing. Started with a single block of wood, shaped it just a little like a brake pad on a band saw, cut the block on an angle to make complementary wedge shapes, trimmed the total thickness to just fit in the caliper with the pistons pushed back.
I've also left the brake pads in place, pressed the pistons all the way in by leaning on the caliper, then inserted wood shims between pad and rotor to keep the piston from moving while flushing.
The whole purpose is just to minimize the amount of fluid in the caliper, so that all the old fluid is replaced by new fluid flowing in. If the pistons are extended, a small amount of old fluid might hide in the cylinder.
EDIT: Idea for using wood blocks came from here, page 5: http://users.rcn.com/dehager/service/abs3_filling_adapter.pdf, which has pictures. Dimensions for the Wethead brakes will probably be different.
I've also left the brake pads in place, pressed the pistons all the way in by leaning on the caliper, then inserted wood shims between pad and rotor to keep the piston from moving while flushing.
The whole purpose is just to minimize the amount of fluid in the caliper, so that all the old fluid is replaced by new fluid flowing in. If the pistons are extended, a small amount of old fluid might hide in the cylinder.
EDIT: Idea for using wood blocks came from here, page 5: http://users.rcn.com/dehager/service/abs3_filling_adapter.pdf, which has pictures. Dimensions for the Wethead brakes will probably be different.
Last edited:
Along with this, my experience has been that “internal” pistons in calipers or master cylinders need a bit of thought on their age. Age will frequently create a rust or corrosion line in the cylinder bores. Movement past that line can instigate a leak as the seal is dragged past the hyper-extension created by the push back of the pistons.
All this of course does have an environmental element to it. Hot, dry areas would lessen it. In a part of the country where you can open the bikes storage area and see it “sweating”, you can be sure all the metal is moist.
OM
Wooden Shims...
When doing a brake bleed/flush I like to get most of the old fluid out of the calipers by pushing the pistons back as far as they will go .
To push the pistons back I use wooden shims you can get at your local hardware store for a $5 or $10. You get six or a dozen.
They are tapered and easy to push into the calipers between the disk and the bake pads.
My procedure is to syphon the front master cylinder then shim both front calipers before starting the bleed/flush procedure.
Then I do the rear caliper the same way.
I believe doing this regularly helps to prevent a ridge from forming and damaging the sealing ring.
When doing a brake bleed/flush I like to get most of the old fluid out of the calipers by pushing the pistons back as far as they will go .
To push the pistons back I use wooden shims you can get at your local hardware store for a $5 or $10. You get six or a dozen.
They are tapered and easy to push into the calipers between the disk and the bake pads.
My procedure is to syphon the front master cylinder then shim both front calipers before starting the bleed/flush procedure.
Then I do the rear caliper the same way.
I believe doing this regularly helps to prevent a ridge from forming and damaging the sealing ring.
