Hi everyone! I'm a newbie of NAM. Nice to meet you guys.

Last week I replaced brake discs and pads for my 2005 R53 and had an issue on the piston of rear brake calliper. The brake discs and pads were changed without any problem.

After I installed them in place, I started the engine and pressed the brake paddle. The first push was spongy and It was getting a normal paddle feeling after pressing the brake paddle twice more.

I turned off the engine and checked the rear brake again. The piston pushed against the brake pad to the brake disc. I couldn't turn the brake disc by hand with ease. (Didn't pull the handbrake lever)

For that, I uninstalled calliper and made an inspection. Pushed and rotated back the piston simultaneously using needle-nose plier (Brake Fluid Reservoir cap opened). Then, I started the engine again and pressed the brake paddle. The piston didn't seem to retract back into position after I unpressed the brake paddle.




My questions are:

1. Does the piston behave normally?

1. Is it possible that some other parts are failing? (like brake master cylinder, brake booster)

1. Any chance that the piston is seized?

Sorry It's a bit TLDR. Thanks in advance for your help.

M

 

I'm thinking you have air in the lines. Next, please clarify something, are you looking for the "piston to return back every time you let off the pedal as it will not? If the piston was seized it would not move out at all.

On brakes, one thing that allot of people overlook are the glides. On my JCW, the front calipers have SS glides that the pads move/slide in, the rears do not. When there are glides, need to make sure they are cleaned/sanded/polished before new pads are installed if new glides are not supplied. There are many times when the piston is not seized but rather the glides are bad that lead to premature rotor wear.

 

In my experience the caliper wont retract back like a spring or anything.. it just hovers over the caliper and the movement from the caliper during corners etc will just sort of push it back slightly so its not dragging.

Your first easy presses are normal after swapping pads because you are taking up that slack from pushing the pistons in to fit the new pads. Once get the firm pedal it should stay firm. If it feels spongy after a day or so, then you probably have air in the lines, do a quick bleed and [top tip] tap on the caliper with a soft mallet to dislodge tiny bubbles while bleeding.

If you feel like the sliders or piston are dragging, you can get the parts to refresh/rebuild the caliper (check ecs?!). You can get a new boot, sliders, grease, etc.

 

Yes, I was thinking, 'the piston would return back every time I let off the pedal' and now it's not as the video. Is it normal that the brake piston behaves like this? or at least R53's?


For 'glides', do you mean the 'clip' at the bottom? If so, they are missing.

 

I'll flush the brake fluid, clean the boot and sliders. Then give it a try. Thank you!!

 

Think about the brake system, when you push the brake pedal it pushes fluid into the caliper that in turn pushes the piston out. Once you let up on the pedal, there is no force to push the piston back in, it remains just off the rotor.

My JCW front calipers have glides, the back did not. Did you fronts have glides and the rears did not?

 

in this pic,




the yellow arrow is the pin/slider I was referring to. pull those out and clean them well, regrease. Maybe replace the boots if they're bad.

 

coincidentally just came across this video.. halfway through he rebuilds the caliper.

 

Your explanation sounds legit. Thanks!
What I thought was, when I let the pedal up, it generates sort of vacuum in the brake line and pull the piston back in.

I don't have glides on both front and rear callipers. Maybe they don't exist on Stock R53.


For installing the pads, is it okay using hi-temp copper grease for lubrication? or specific brake-pad paste? Thanks

 

Yea, there's a thin layer of deposit on these pins. (maybe it's from the rubber boots?) I'll clean them all. Thanks.

 

FYI: My 06/R53 has Guide Pins on both Front and Rear. Calipers are stock. Item 6 on your diagram is a guide pin.

 

For clarification, I am talking the glide not guide. The glide is the C/U shaped item in Post # 4. Both glide and guide should be cleaned during the pad change.

While the OEM is displayed, when the calipers are stock color, I like to paint # 4 red. It gives it a nice contrast.

 

Thanks for clarification. I’m wondering, it seems that it’s a must to have the glides for fitting the pads. But I couldn’t find them from parts diagram nor online car parts shop.

Haha I never think about painting the little clip. Sounds interesting. If I need a new set of calipers I would powdercoat to pepper white as the body paint colour.

Do you have those C/U shape clip glides in your Stock r53 brake calipers?

 

No, I do not.

 

There is a special lube for brake guides, pretty sure it is not cooper but rather some type of special synthetic or lithium.

 

I use this:

 

Everything seems to be sorted Thanks everyone!

 

I changed rotors on the rear and could not for the life of me get the pistons to retract much, even when opening the bleed valve. I got the rotors in, but doesn't seem right. Did not even install new pads. The old ones were not worn much...

I have a piston retraction tool and the piston just seemed like it moved a very small amount. The parking brake was not on, but something doesn't seem right about it.
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Edit: I just found this:

Replacing the brake pads is simple. You remove 2 bolts which frees the caliper/piston assembly. You replace the old pads with new ones, and put it back together. The trick lies in compressing the piston. With the front brakes, you just push it in, with the rear brakes you need to use a tool that pushes in and twists at the same time, so the Brake Tool I show here is the idea tool to have. Each wheel will probably take between 20 to 30 minutes.

Okay, mystery solved. I know what to do...

 

Yes I rented a wind back tool at Autozone but it did not have the correct adapter. I had to fashion my own out of a disk of plastic with a couple screws sticking out of it. Its kind of a PITA job, but the new brembo pads and disks I put on work great.

 

For anyone working on the rear brakes, make sure the rear pad is seated correctly. The piston has a lip, where the retaining clips on the inner brake pad should clip on! You will see this mentioned almost nowhere.

I was searching for spongy brake pedal and got 1 relevant result which talked about it. I documented it, so please learn from my mistake!

The lip on the rear caliper piston



The retaining clips on the inner rear brake pad



How it should sit before fitting them