79 Special Brake Help Needed

[smuscarella]

Hey guys,
I'm stumped on fixing my front brakes. Last year I had underwhelming brake power in addition to an alarming rattle, so I decided to at least change the pads this spring and install the special retainer clips.

1. Got the pads out and got the classic shock that they're slanted. Was relieved to find out that's normal
2. But then I could not for the life of me push back the piston
3. So I removed calipers and disassembled, cleaned, and knocked down a couple small burrs that were making the piston hard to move. By the end of that process I was able to reassemble and push the piston back manually.
4. I went to reinstall with the new pads and did not have the clearance to put the new pads in. It was as if the new pads were too big to fit on the rotor and in the caliper. The issue appears to be alignment related. I've read about alignment issues, but not sure how that works. This is my first major dilemma. I tried the old, worn down pads and they fit, but just barely. Lots of rubbing. So first big question is:

What tricks do I need to know to properly reattach the caliper with the new pads? I read a post that discussed the height problem with the washer. My problem is left to right alignment though. In order to get the mounting bolt on I have to push the caliper to one side which then creates the issue of fitting both pads.





Next issue is bleeding the brakes. I tried manually to no avail. Then I bought a pneumatic bleeder and got the same abysmal results. What are the symptoms of a clogged and/or poorly functioning brake master cylinder?

[TopCatGr58]

Hey there,

First, I fixed your original photo links. When you view your photos in the Imgur site, click on the button in the lower right corner that says get links, then look at the list of links in the window on the right side, select and copy the ones for BBC...will have just {img}....url..{/img}....but will have brackets [] instead of these fancy paranthesis {}, copy all and paste into message and then they will appear. Our site will then resize them to fit, but allow folks to click on them to view the full size image.

I can't tell much from your photos though....aside from seeing that the mounting bolt isn't lining up. I hate to say it, but are you sure you're putting the correct caliper on the correct side, they are right and left specific, same with the pads.

As for bleeding, if you've taken the line from the master cylinder, then folks find they need to first BENCH BLEED the master to ensure getting fluid coming out of the hole, and then reattach to the lines. You can place a piece of wood between the pads, have the calipers still loose/off the forks, position them on a box or something to get them even/higher than the MC, to help the bubbles flow UP to and finally out of the calipers. Then once you have good FEEL at the MC, then put them on the forks.

T.C.

[BA80]

+1 on the calipers and the pads being side specific.

[smuscarella]

Thanks TopCat!

I did check for left and right, but I'll check again as you're right, it does look like I could have screwed that up.

I haven't removed the master cylinder, but will probably do that, clean, and bench bleed like you mentioned.

[TADracer]

Special front brakes are wierd things!

If you cannot get your pistons to operate smoothly and retract all the way into the caliper body then you need to remedy that! If everything is right in there, you should be able to take a small C-clamp and gently retract the piston until it bottoms. If you cannot retract the piston until the dust boot is virtually flush with the caliper surface then you should stop right there and clean/re-build your calipers. You need to get the piston all the way in for clearance with new pads.

One other thing you should look for is bent through bolts. Some special brakes have the tendency to slightly bend the bolt at the threads when they seat under the first hard braking. If they are bent it is almost impossible to hit that sweet spot again and get a good alignment of the calipers. To check, look at the caliper when you turn the bolt into the fork. If the caliper seems to go side to side a bit then you should replace the bolt. They can be had at any hardware store.

[smuscarella]

So it turns out the only thing I did wrong was that I did not retract the caliper enough. After I cleaned them out, I was able to push them back by hand. What I thought was fully retracted was in fact still about 1/8" out. I was able to retract them fully with a c-clamp and everything went back together perfectly. Once back together correctly, it turns out all my efforts at brake bleeding were in fact successful, too.

Amazing to have brakes again and a little lesson in paying attention to the small details of procedure.

Just some spark plugs and a headlight wiring problem and she'll be 100% back...until the next thing.

Thanks for the help guys.