Issues with replacing brake pads

[adam h]

Hi all!  

This is my first post.  I have a '72 CB750 that has sat for a few years.  I am motivated to do a good bit of the "fix-it" work myself though admittedly much of this will be a learning curve for me.  

The brakes were sticking so I took apart the calipers, cleaned them out good (took off rust and varnish), greased them, and put on new brake pads.  The pads seem quite a bit thicker than the previous ones (which I know makes sense for new pads), and they are the ones the shop said were compatible.  When I put it all back together, pads appear to be clamping the rotor.  I backed out the swing arm screw significantly but at a certain point even though the lock nut is loose,when I back out the screw it doesn't want to move any more. (It turns but the spring is not pushing it backwards) The inner pad sticks out from the caliper fully whereas the outer pad is recessed in the caliper all but 1/16th of an inch.  I wouldn't think these are the wrong pads but I'm surprised at how tight it all fits and how much the inner pad is protruding compared to the outer pad.

My question is What might be preventing the adjustment screw from backing out further so that I can properly set the inner pad clearance?  

Surprisingly, I can walk the bike forward and when I apply the brakes it properly stops the bike.  

Is this normal?  Do I just need to TIGHTEN up the adjustment screw and call it good?  From here, What is the best way to adjust the brakes properly?

Any thoughts would be most appreciated.

AH

[pat english]

disc brakes always rub a lil bit..

[TOOLS1]

This is normal! Adjust the breaks, so that a piece of paper will just slide between the pad, and the rotor.
TOOLS

[Piute]

If I looked down at my pads (dual disc brakes) they do look like there touching but are loose and haven't squeaked at all.my 77 is lot diff then yo 72,advanced a bit has lots of keepers and bowed spacer.
   Welcome and enjoy your build,

[81SuperChris]

Hi TOOLS,
I've also replaced my pads (1981cb750F) and they now seem so thick I can't get the caliper back on the disc... They're the dual piston calipers.

What should my next step be?

Cheers!

[TOOLS1]

Just sand them down to fit.
TOOLS

[Re-run]

Have you made absolutely sure the pistons are pushed all the way back in? Some times a person, especially if it is their first brake job, won't get the pistons all the way in and the pads stick out too far then.

[81SuperChris]

Thanks for the advice ReRun and TOOLS,

I couldn't move the pistons with my own hand force, so took them to a local shop and they recommended I buy the parts myself and bring it all in to them to minimize my costs - nice guys hey? I also get the idea that caliper rebuilding isn't the most fun.

Regardless I'm making progress. Hopefully in 3 weeks I'll have her running!

Cheers,
Chris

[TOOLS1]

WHAT? Caliper rebuilding is one of the easiest things to do on a vehicle. I can rebuild them in less then 15 minutes, unless they are really stuck, and then it takes 30 minutes. I put a rag between the piston and the caliper, make sure my fingers are not in the way, and then use a rubber tipped blow gun on my air hose to blow air into the caliper. This should pop the piston right out. If it does not, then I hook it up to a master cylinder, and use that to pump it out. Then I clean up the piston with some solvent. Remove the rubber parts from the caliper, and clean it with a wire wheel on my Dremel tool, making sure to get the grove for the O-ring clean. Then install the new O-ring, and dust seal. Lube with brake fluid, Apply a little air to the caliper as you hold the piston to the dust seal, this will blow the dust seal out around the piston, or just work it around with a small screwdriver. Then shove the piston down into the caliper. DONE! Yea, those nice guys will be happy to separate you from $50.00 for doing it for you.
TOOLS

[shinyribs]

Did you open the bleed screw when you tired to push the piston back? It gives the fluid an easier path to escape the retracting piston.

[81SuperChris]

No I didn't Shinyribs, I'll try that tomorrow! Thanks for the tips TOOLS - I have all of that in my garage but the rebuild kit. I'll definitely give your way a try before taking it in, I'd rather learn and save money than do neither!

I'll update you if I have any issues once the parts come in, thanks

[81SuperChris]

Hey Tools,
I put the calipers back onto the bike, bled them and then used the master cylinder to try and push out the pistons - but I only got one!. It seems like the other three are really stuck. I don't have access to an air compressor.
Do you or anyone else know any other ways to get pistons out of a caliper? I could use vice grips but that would mean replacing them and I'd prefer to learn how to refurbish these ones.

Cheers!

[TOOLS1]

You could try a master cylinder off a car. Those have more power. If a master cylinder will not push the piston out, you will need to resort to destructive measures. You could drill a hole in the back of the caliper to insert a bolt, and press the piston out. Then afterwards tap the hole for a pipe plug.
TOOLS

[Beekeeper]

Put the piston that came out, back in.  Use a C clamp to compress it, then place a block between that piston and the caliper.  It will force the pressure to your stuck piston.