Brake Caliper Teardown (yes, with pictures!)

swooshdave said:

chopped850 said:

Simply attach the grease gun to the zerk fitting and pump away. If the grease dosn't push the pistons out then throw the caliper away and start fresh. But they will come out. Leave the back cap on so both pistons push out. Remove the brake pads of course.

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Zerk? Do you mean bleeder valve?

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Yup!

chopped850 said:

swooshdave said:

chopped850 said:

Simply attach the grease gun to the zerk fitting and pump away. If the grease dosn't push the pistons out then throw the caliper away and start fresh. But they will come out. Leave the back cap on so both pistons push out. Remove the brake pads of course.

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Zerk? Do you mean bleeder valve?

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Yup!

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Going to try this. Need to break out more heat just to loosen the bleeder valve and then find a bolt to block the other hole. Three day weekend, let's see if I can get a few minutes in what the wife calls, "Manland".

I had thought of another way to make a peg spanner.

Something like this (on ebay for $30 :shock: ) but maybe weld an old socket to the other side. If heat and my $4 spanner work I'll be a happy camper.

Some good information on caliper rebuilding can be found here…

http://www.captain.norton.clara.net/pga.html#mtp top

2Wheels said:

Some good information on caliper rebuilding can be found here…

http://www.captain.norton.clara.net/pga.html#mtp top

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This part really worked slick for me for getting the inner piston out that had been unmoved in 35 years.

>>Taking the caliper off the fork leg and disconnecting the hydraulic pipe is not normally a problem, but what you have to remember, is that its a whole lot easier to remove the inner piston from the caliper if you remove the pad and pump the brake lever to push the inner piston out. This should be done with the outer piston pushed as far out as possible. Keep it's pad in position and hold it there with a screwdriver inserted where the disk usually runs. taking the pad off the inter piston allows it enough room to move.

Once the inner piston is as far out as possible, (and it can come out past the seal, so be careful to catch the fluid), you can remove the caliper from the bike and place it on the bench for disassembly. <<

I got my coverplate off by using 2 1/4" bollt shanks (i.e. threads cut off) clamped in the vice at the correct spacing, and with the caliper attached to the fork leg I got plenty of purchase.
Naturally, this is fine if your fork leg isn't attached to the bike :roll:

Totally agree with 79x100 regarding the inner piston - once I'd driven mine back in it came out with compressed air. If the chamber is pre-wetted with penetrating oil this frees it off OK.

The outer piston required 2 tyre levers back-to back with a socket in-between as a reverse scissors action to clamp against the inner bore of the piston (Imagine expanding circlip pliers), worked fine for the one I had.

As for drilling and tapping....why not drill out the piston instead? they're almost guaranteed to be scrap anyway :wink:
This could be used for both pistons, I guess...

This might just turn into a story, but on the other hand it might work on a caliper that is stuck.

Recenlty I had to swap out a cast iron boiler section because it was cracked. Got the 600 lb lump moved outside and the new one in place, but the biggest problem was that in order to hook it up we needed the 6-inch black iron pipe nipple out of the old one. I put a ten foot cheater bar on a 48-inch pipe wrench and using the hydralics on my Bobcat loader picked the front end of the loader up by pushing down on the cheater bar. No give. This is where you tell any spectators to stand back because when the thing gives something is going flying. I didn't calculate the torque applied but it was considerable.

Somebody I talked to convinced me to smear the joint where the nipple entered the section with anti-seize and then apply heat. The claim was that the temperature difference would suck the anti-seize into the joint. I was skeptical to say the least. This was an old rusty boiler section that had been heated and cooled for years, with water flowing thru it. But then when you can't find other options you try even stupid ideas. This operation took a BIG torch because of the mass of the project but after some heating and catching the anti-seize on fire at least twice, the original pipe wrench backed out the nipple without the cheater and Bobcat involved.

I don't happen to have a stuck caliper to experiment on. But if I did, I would give it a go, just in case. I would love to hear back on it.

Now with any apologies to Dave for hijacking his thread, what is the deal with a smaller diameter master cylinder? That is counter intuitive to me. Seems like you should be pushing more fluid with the master not less. What am I missing? Or does this give the hand-lever a greater mechanical advantage to develope more pressure?

Russ

B+Bogus said:

As for drilling and tapping....why not drill out the piston instead? they're almost guaranteed to be scrap anyway :wink:
This could be used for both pistons, I guess...

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Yep, done that many times and it has worked fine. Once I get the hole tapped, I've loctited a bolt in, and twisted the piston out.

rvich said:

Now with any apologies to Dave for hijacking his thread, what is the deal with a smaller diameter master cylinder? That is counter intuitive to me. Seems like you should be pushing more fluid with the master not less. What am I missing? Or does this give the hand-lever a greater mechanical advantage to develope more pressure?

Russ

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Considering that I tend to hijack my own threads, no apologies needed. :mrgreen:

Search for master cylinders to learn all about the magic of making a Norton front brake unsuck.

rvich said:

Now with any apologies to Dave for hijacking his thread, what is the deal with a smaller diameter master cylinder? That is counter intuitive to me. Seems like you should be pushing more fluid with the master not less. What am I missing? Or does this give the hand-lever a greater mechanical advantage to develope more pressure?

Russ

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It seems this was an oversight in the original design. As other leading manufacturers have determined the smaller bore gives a more appropriate mechanical advantage. More info here:

http://www.vintagebrake.com/mastercylinder.htm

And good news.

I applied some heat with a handheld propane torch. Aluminum doesn't take long to heat up, applied some air and pop, both pistons came loose.


A bit more heat around the plug and it came right off with my new friend, the peg spanner. I removed the outside seal and the first piston wiggled out. Then I turned the caliper over and tapped it firmly and the other piston came out.


All apart.

Next up is a quick trip to the blast cabinet (because of constrained space in my garage it's over at my cousin's. He's about 15 miles away so I hope to get over there later tonite. Mostly to clean up the outside and just a touch on the inside. Someone painted the area between the "fins" black, which I don't know if I like or not. Was it from the factory like that?

After a cleanup the caliper can go back together and it's one less thing on my long list.

Something really nice that I checked out is that the peg spanner looks like it will also work on the clutch release locking ring, provided it doesn't require too much torque.

I have to say your pretty lucky. The hard chrome on my inner piston had chipped and started to rust. I made a spanner with 2 bolts and a piece of metal drilled out to the right width to remove the plug. To get the inner puck out I used the biggest easy out I could find. Worked like a charm.... no soaking, no heat, no drilling through the caliper.

Heres your next step.

And after being turned an painted.

Maxxfli said:

I have to say your pretty lucky. The hard chrome on my inner piston had chipped and started to rust. I made a spanner with 2 bolts and a piece of metal drilled out to the right width to remove the plug. To get the inner puck out I used the biggest easy out I could find. Worked like a charm.... no soaking, no heat, no drilling through the caliper.
Heres your next step.
And after being turned an painted.

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Actually it was the heat that did the trick. The aluminum expands so much more quickly than the pucks that it made it easy.

You think you're joking about the disc, but wait till I post a picture of the disk I have!

Got the caliper blasted. It's was pretty clean so mostly to get any last residue and take the paint off.

Before:


After:

Just a little 1000 grit on the areas I wanted a little shinier. Then a little aluminum polish and that's good enough.

There are new pucks and I thought there was a brake rebuild kit but there wasn't. So this part is on hold until I can get one ordered.

The rebuild kit consists of 3 new seals. 1 for each piston and 1 for the cover. OldBritt's has them.

swooshdave said:

I applied some heat with a handheld propane torch.

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The good ol' fire wrench to the rescue.

swooshdave said:

The first thing I was trying to figure out is where to get a peg spanner. I happened to be at my favorite Chinese import palace (Harbor Freight) and spotted a peg spanner (adjustable) by the saw blades. I think it's for removing the saw or stones on an angle grinder. For $4 I got it and guess what? The pins are slightly smaller but at least they fit in.

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It's always neat when you can improvise when you don't have that special tool as long as you don't deface your valuable parts in the process. Here's my free peg spanner:



It was midnight and I didn't have one so... I'm the kind of guy who doesn't toss much out. Steel rods get tossed into my punches, chisels and drifts drawer of my tool box and I happened to have 2 that were a tight fit. The rods were long enough to keep parallel so there was little chance of putting the bores out of round before I got it off. Didn't need that socket on the end to keep em parallel, just hand pressure was enough. A flat file served as the handle. This caliper sat for a good 25 years on the bike but I'd sprayed it with WD40 for 3-4 days prior. It came off easily.

I have to pick up some grease before I attempt to get the pucks out. There's enough ideas here that I should get em out ok.

RennieK said:

It was midnight and I didn't have one so... I'm the kind of guy who doesn't toss much out. Steel rods get tossed into my punches, chisels and drifts drawer of my tool box and I happened to have 2 that were a tight fit. The rods were long enough to keep parallel so there was little chance of putting the bores out of round before I got it off. Didn't need that socket on the end to keep em parallel, just hand pressure was enough. A flat file served as the handle. This caliper sat for a good 25 years on the bike but I'd sprayed it with WD40 for 3-4 days prior. It came off easily.

I have to pick up some grease before I attempt to get the pucks out. There's enough ideas here that I should get em out ok.

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Try heat and air before you go the grease route. When dealing with aluminum and steel this is ideal. :mrgreen:

rvich said:

.... what is the deal with a smaller diameter master cylinder?

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Very simple: Pressure is Force divided by area: P = F/A . If F_MC stays the same P goes up if A_MC gets smaller.

If the piston area in the caliper stays the same for the very same reason the braking force goes up: F_piston = P*A_piston down there.

That is counter intuitive to me. Seems like you should be pushing more fluid with the master not less. What am I missing? Or does this give the hand-lever a greater mechanical advantage to develope more pressure?

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Yep, but actually your intuition was at least partially right: If the swept volume is too low the piston will not reach the disc....


Tim

swooshdave said:

Try heat and air before you go the grease route. When dealing with aluminum and steel this is ideal. :mrgreen:

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I still don't have a compressor.