Topic: Stuck front new disc brake pad in CB550 after reassembly

[neurotoxin312]

Hey guys. Just took apart my front disc brake caliper from my 76' CB550 for inspection. Managed to get everything apart and cleaned. When I installed the brake pad for the piston side there was quite a bit of resistance. I greased the sides and pressed it in with a C clamp. When I attach it to my brake lines and I pump things up everything on the piston side refuses to move. Any suggestions without damaging the new brake pad? Thanks.

[flybox1]

was this a new pad with paint on the metal backer? did you sand it off?
was the piston pitted? was the inside of the caliper spotless?
new or reused caliper o-ring?

[neurotoxin312]

Ah crap... Was I suppose to sand off the paint? These are brand new pads. Right now its stuck inside the piston body. I sprayed some PB blaster and letting it sit for a few hours. Not sure what to do at this point...Any ideas?

1. Piston was cleaned and polished although it did take some effort to go in (I used a c clamp)
2. I reused the O ring. It appears to be in good condition.

[neurotoxin312]

It's only required if it requires you to ram it home with a clamp... Brake pads should not fit that tightly, else, guess what? They won't function. Now you can remove the hard line and attach a grease gun to pump out the stuck piston and pad. Then clean all that out and start over.

If your pad won't slip in smoothly, sand the edges to be free of paint. New pads are made at much higher tolerances than 40 year old cast calipers. All too frequently they are a few thousands too large.

I tried using my hydraulic brake and master cylinder to remove the brake pad and piston. That didn't work. 1. Is the grease gun trick better than using your brake setup? The thing is really jammed in there unfortunately.

Should I just get a new caliper?

One more question
2. Is the caliper piston suppose to be forced in also? or is it suppose to slide in easily? ( I had to use a c clamp to get mine in)

[jonda500]

If you clean residues off the calipre bore with scotch brite and lubricate the piston with brake fluid, it should push in quite easily- you may have to loosen the bleed screw if the system is full of fluid though.

When I fitted new aftermarket pads I did have to remove the black paint from around the circuference to make them fit. They should just slip in easily I thought.

[neurotoxin312]

Awesome. Makes a little more sense now. Can I get this grease gun and the fittings from home depot? What adaptor do I need for the grease gun to bleeder valve? and what size bolt screws into the caliper to block it off? Thanks.

[neurotoxin312]

Awesome. I'll try that tomorrow. When I was trying today with my brake line connected I could hear the friction of the piston pushing on the pad. I think that the pad is really stuck in there unfortunately. I'll try the grease gun method tomorrow to see what happens.

[neurotoxin312]

Holy cow... I am utterly dumb founded at this experience. I have to admit that I had my doubts...The grease gun method works! and it's amazing! It can be done with a Lucas grease gun purchased from Home Depot. The standard 1/8" npt hose that comes with threads in about 8 or so turns which is just enough to hold the pressure. When I started filling the caliper up that piston moved without a problem! Just for the record, using grease as the hydraulic mechanism is WAYY stronger than connecting your caliper back to the brakeline & stronger/safe than compressed air. For clean up I just wiped everything down, soaked in brake cleaner, and used a little compressed air to blow everything away. I also removed the caliper piston seal and used fine steel wool to clear off the gunk on it with some WD40, then re installed.After that, I sanded the paint off the new brake pads and they installed just right! Everything is nice and smooth now awaiting installation on the front with some braided stainless steel lines! Thanks guys!

I attached pictures of what things looked like for references.