Topic: front brake caliper question-need clarification please

[Bikebuff]

Hello All,

I have a front caliper from a '69 cb750 (I'm doing the dual disc conversion, so the caliper in question is not connected to any brake line or master cylinder).  The brake pad and piston are still in the caliper.  I read on the forum that you can use a grease gun or compressed air hose to get the piston out, but does that also apply to getting the brake pad out too?   Since this is my first time rebuilding the caliper, I'm going to try the grease gun idea with a zerk fitting.

Sorry for the rambling, but I can't get the pad (and the piston) out.


Thanks!!

[Bikebuff]

Anyone?? Anyone??  Bueller?? Bueller??

[oldfordguy]

The brake pad isn't attached in any way, so it will come out/off first when pushing out the piston.  The grease gun in the way to go if it is really stuck in there, its a little messier but not as dangerous as compressed air.
Matt

[Bikebuff]

Thanks oldfordguy-I was having a tough time with it yesterday.  I didn't have the zerk fitting but will be getting one today to speed things up a little.  And clean up the grease I've spilled so far-it turns out I was wrong trying to fit the end of the grease gun onto the bleeder with no success (but plenty of grease everywhere  )

Will aerosol brake cleaner dissolve the grease after I get the piston out and cleaned up?  I'd like to have everything SUPER clean prior to hooking up the new brake lines-don't want grease coursing through the brake lines.

[Bob Wessner]

And clean up the grease I've spilled so far-it turns out I was trying to fit the end of the grease gun onto the bleeder with no success (but plenty of grease everywhere  )

I've used the grease gun approach with success also. I'm not sure how large a grease gun you are using, but I have a small cartridge one I use for the swing arm lubing. If I remove the fitting, the threaded end is small, but NOT a match. I wrapped in in a few turns of teflon tape first, then sort of lightly screwed it in to where the brake line attaches to the caliper. It doesn't take that much of a seal to work. A couple of pumps and it was out.

[Bikebuff]

That's what I like about this site-people willing to help out with whatever a fellow SOHC'r needs.  Thanks everyone. 

I've used the grease gun approach with success also. I'm not sure how large a grease gun you are using, but I have a small cartridge one I use for the swing arm lubing. If I remove the fitting, the threaded end is small, but NOT a match. I wrapped in in a few turns of teflon tape first, then sort of lightly screwed it in to where the brake line attaches to the caliper. It doesn't take that much of a seal to work. A couple of pumps and it was out.

Well, there's my second problem-I didn't remove the fitting, which explains why I didn't get anywhere last night.  Thanks Bob-I've got the larger grease gun than the smaller one you have.  Thanks again.  I hope to have more positive results to post tonight.

[super pasty white guy]

You may not even need a zerk.  My gun will clamp onto the bleeder w/o problems.  I just replace the banjo bolt with a solid bolt and have at it.

Dave

[bryanj]

What Bob meant was leave the bleed nipple in and tight and then fit the thread on the end of the gun pipe (with zerk, or whatever, fitting removed) into where the brake pipe goes. It IS NOT the correct thread so DO NOT keep tightening but it does tighten enough to work, I have done  loads, usually with a comercial air operated grease gun.
Dig out the grease with fingers, clean with kerosene and finish with brake cleaner after cleaning the crap out of the seal groove

[Bob Wessner]

Yup, that's what Bob meant but didn't explain very well.

[Bikebuff]

A huge Thank You to everyone who helped with my dilemma.  I used the grease gun, per Bob's recommendation and it worked!  This being my first time rebuilding brakes, I'm over the moon about this (yeah, I'm easily amused ).  The piston came out, I clean up the grease and junk and the caliper is looking mighty good.

However....

I've got a problem with the smaller half of the caliper that bolts onto the larger portion.  I tried to tap out the pad, and the pin freed itself from the pad.  I've got no leverage whatsoever to get the pad out.  I've sprayed WD-40 and let it sit overnight with the hopes of it maybe loosening up.  No luck this morning.

How do I get this pad out now?  Dynomite?  Grenades? Burning Effigies?

Help!

[Bob Wessner]

First let me say I have never been faced with this, so take that into consideration. Maybe someone else has a better idea. If were faced with this, I might consider drilling a small hole into the face of the pad, being careful not to go too deep and through the pad plate, then screw in a wood screw and try to grasp it with pliers or something and wiggle it out.

[Jonesy]

If you can anchor the caliper part in a vice or some other sturdy arrangement, you can chip away at the friction material with a hammer and an old screwdriver. Chip away at the edges of the brake pad to free it. You might also try to grip the edges of the pad with large channelock pliers and see if you can twist it back and forth, since you've already driven out the retainer pin.

[Bikebuff]

I was thinking about doing something like that last night but it was pretty late (0130AM CDT) so I figured maybe getting some rest would keep me from making a huge and potentially damaging mistake.  The brake pad material separated from the pad backing last night (a detail I neglected to mention in my post this morning), which is making my dilemma a head-scratcher.  I will give it try tonight, but I agree with you that I'm going to have to be very careful so as to not to damage the inner face, so to speak.

I've also got an old feeler gauge, I wonder if I can get one underneath the outer edge to at least free it from the inner face (imagine using spatula on a grill/griddle to free a burger or chicken breast from the surface without it breaking apart)?

I'll post my results when I get home and have at it again.

[Bodi]

Probably the steel plate has rusted and jammed at the edges.
You could heat the steel pad backing plate with a torch until it's very hot, waiting a minute, and then pressing an ice sube against the plate. The sudden change in size as it cools down might break it free, the aluminum caliper part will stay hot and "large" longer than the steel plate. Heat might damage the caliper paint, though.
The backing plates usually have a dimple on centre so that the pad can float to the right angel for the disc. Laying the caliper half on something solid then whacking the plate down around the edges will want to make it rock, freeing the stuck edges maybe.
Soaking the whole thing in Coke for a day or so should loosen any rust, the weak phosphoric acid attacks rust but shouldn't bother the alloy caliper or paint.

[Bikebuff]

Okay....progress from last night: success!!!

I was able to get the pad off the backing plate.  I started by soaking the plate in a cup of Coca-Cola (thanks Bodi for the suggestion).  That seemed to help loosen the rust up.  I eventually found a long and narrow nail and tapped the brake pad from front side through the pinhole.  About a dozen or so gentle taps on the nail with a hammer and presto!  Brake pad out with no damage to the inner our outer plate!


Thanks again everyone for your suggestions and thoughts-your help has been a tremendous boost for me (raises glass and toasts the fellow SOHC'rs).

Prost!

[Bob Wessner]

Congratulations.

It it weren't for brakes and carbs, there would be nothing to do on these old bikes.