Sanity check, rear brake edition

[Joepi5]

Ello,

Yesterday I replaced the seals, pad mounting hardware, slide pin boots, pads and rear disc (no problems on the bolts fortunately, didn't even need heat) on my bike. I suspected the caliper piston or slide pins were stuck (the red paint on my brembo pads melted/burned of it).

I only used OEM BMW parts (except for the disc, which is a brembo one) bought from the dealer. Today after the first test ride to work and back I decided to check rotation of my rear wheel and the temperature of the caliper. It seems cooler now, despite using it more than normal during the ride home. The pads do not come completely off the disc, I hear them in contact during the whole rotation. Is the noise in the video below on par with the rest of you? Or is it too much noise?

And if it's to much, what could be the issue? And how to resolve that potential issue?

 

[squibb34]

Clearly not as it should be - maybe drop the pads out & check the pad & disc surfaces.

Could it be the caliper body touching the disc? I can't see how the caliper & pads are sited from the video.

 

[Joepi5]

Clearly not as it should be - maybe drop the pads out & check the pad & disc surfaces.

Could it be the caliper body touching the disc? I can't see how the caliper & pads are sited from the video.

Without the pads the disc rubs the anti-rattle spring. Without that spring nothing touches. Disc look like new. Pads have some discoloration on the pads material.

It's like the pistons dont retract enough after applying brake.

 

[squibb34]

Without the pads the disc rubs the anti-rattle spring. Without that spring nothing touches. Disc look like new. Pads have some discoloration on the pads material.

It's like the pistons dont retract enough after applying brake.

You have new piston seals. Presumably you cleaned the pistons & seal grooves carefully. The seals are not directional, so there is no seal lip to orientate - the grooves are machined to distort the seals slightly & hence allow a minute retraction of both pistons once the brake is released. Then the pins - does the caliper slide freely; is Is the caliper body still in good condition or are the pin guide holes corroded? Then there is the support plate - the stainless steel anti-rattle support plate needs to be snapped cleanly into its exact locating position inside the caliper bracket & must not be crooked or have dropped out of position during fitting.

This is one of many caliper strip videos on YouTube - it maybe worth checking it out: -

Aside from this, is there any obstruction in the rear hydraulic line that could create residual pressure. Sometimes, the rear brake pedal gets adjusted for rider comfort without checking whether the brake still releases hydraulic pressure fully. Without the caliper fitted, presumably the noise has gone - if not, then it could be driveshaft UJ or spline related.

 

[Joepi5]

I used that exact video as guidance. The rattle spring is also new, as is the support plate. Everything except the caliper body and the mounting bracket is brand new. This evening I fitted every (except the seals & pistons again).

The carrier slide freely and returns to it's resting position after you push them in. This was the main reason for the overhaul, the previous slide pin rubbers were swollen and didn't seal tightly anymore. The one in the caliper plate pinched the pin which caused stiff movement.

One thing might cause residual pressure is the diaphragm in the reservoir, it fits very tightly in there. Maybe pressing the pedal causes Enough pressure to actuate the brake, but doesn't relax afterwards to fully release the pressure. The fluid level is halfway between full and low. Socthat shouldn't be to much.

Strange thing js that during riding the rear brake operates as expected.

 

[botus]

get the caliper off and spin the wheel / check for wheel bearing slop

my rear bevel went from normal to collapsed and loads of nasty play in 2 weeks and 50 miles

 

[JoeBiff]

I experienced same when I renewed rear pads.
After a hundred Km, everything returned to “normal” once the pads bedded-in

 

[Santa-2512]

I'm just on the way to collect mine, new/ refurbished / rebuilt abs unit fitted,

My symptoms were randomly applied front brake lol. I thought it was sticky calipers, and had them stripped and cleaned

Turns out it wasn't lol

 

[Joepi5]

I'm just on the way to collect mine, new/ refurbished / rebuilt abs unit fitted,

My symptoms were randomly applied front brake lol. I thought it was sticky calipers, and had them stripped and cleaned

Turns out it wasn't lol

The servo brakes ABS type? Or the later type? Either way that sounds bad

 

[Santa-2512]

No not servo thank god, just STD abs

One circuit was playing up

Literally just got it back now,

Seems very agricultural, compared to the wing lol

 

[Udders]

Are you sure the brake pipes aren’t knackered inside?
They may look ok from the outside but can swell up on the inside leaving pressure on the system.
If they’re the original pipes it may be worth changing them.

 

[Joepi5]

get the caliper off and spin the wheel / check for wheel bearing slop

my rear bevel went from normal to collapsed and loads of nasty play in 2 weeks and 50 miles

All is fine in that department.

 

[Joepi5]

Are you sure the brake pipes aren’t knackered inside?
They may look ok from the outside but can swell up on the inside leaving pressure on the system.
If they’re the original pipes it may be worth changing them.

Anyway to check or just replace it? Could it also be the master cylinder?

Bike is a 2010 model with 45k miles on the clock.

 

[Santa-2512]

I thought that when mine started playing up

My mech bled and worked back from caliper to master all ok,,but abs connected, and it just locked everything up on the front circuit


Just got it back , seems ok.