Brake caliper overhaul questions

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Danno

Danno

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I've succeeded in getting the screw-in cap off by way of penetrant and the judicious application of heat, and pried the piston behind it out.

1. What is the trick to getting the inner piston out? Everything was rusted, crusted and froze solid. It's soaking in PB Blaster right now.

2. Are the pistons hard-chromed or otherwise plated? Seems to be a bit of rust damage to the outer surface that was behind the pad but beyind the seal. Can I take this out with some fine emery cloth or should they be scrapped? I've noticed the steel sleeve in the bore and I think I can clean that up sufficiently.
 
Congrates on straight forward cap removal which is a good omen the pucks may be re-usable - but may be rust-pitted enough ya do not want to re-use or can't reuse so a few ways to trash old inner one out, weld a rod on it and pull out by pliers , drill press a hole in puck then run a tap in and use its threaded grip to lift drill press chuck up with puck hanging on the end to re-use a paper weight. I prefer to drill hole in back of caliper [ruining perfectly nice semi-hidden area looks] to drift the puck out then re-seal with a allen head and locktite. There's hand full of other ways air to oil to grease pumping to remover and save the rusty pitted puck that then can be cleaned up really nice till revealing how much you don't want to re-use it anyway so spend on SS kind. IF puck is still in savable condition then some magnets on it to add mass and some heat on shell then some slamming on wood should creep it out some on *each* hard slam, if not then plan B, C, D...
 
I had a similar issue with one of my rebuilds, heated the very centre of the inner piston with a oxy/acet flame using a brazing tip to keep the flame as narrow as possible, kept heating until the whole thing was smoking hot, this will break down the old piston seal , used a set of circlip pliers on the inner edges of the piston, you can get just enough purchase to rock/remove the piston. may have to repeat the cycle a few times.
Hope this helps
Regards Mike
 
Here's how I was able to remove a really stuck inner piston:
Find the piston center on the back of the caliper, drill and then tap the hole, then use a drift into the hole and press/vise pressure or a threaded bolt to push on the back of the piston.

Lots of corrosion on the piston skirt. A set screw and thread sealant/JB Weld used to close the hole.
Brake caliper overhaul questions
 
The drill-and-tap method sounds the best since I have bits, taps and stainless set screws. Thanks for the replies on that. Now, what about the pistons? Are they re-usable with some cleanup? The one I have out isn't nearly as ate up as the one in Bob Z's illustration.
 
Ugh!!!! if you are gonna risk permanent forum banishment by drilling a non factory hole > where it might be seen- *** Please*** no one else JBW in the plug >>> as it will now tempt next fella [unless alerted] to attempt removing it but will twist up the allen wrench as it smears the hex inside plug so will have to drill a larger hole to save the caliper shell. To have a semi chance remove JBW'd plug in this application it may take 450-500'F to soften enough to have a change to remove and only use mild sealant gripper like blue loctite or RTV. Of course if SS pucks put in then likely can get out in future normally. The ultimate-optimal Nortoneers on this forum knowing they'd face other similar judges would have to weld fil hole and re-polish better than new, which sounds easier better path than trying to remove smallish plug JBW in.
 
Danno said:
The drill-and-tap method sounds the best since I have bits, taps and stainless set screws. Thanks for the replies on that. Now, what about the pistons? Are they re-usable with some cleanup? The one I have out isn't nearly as ate up as the one in Bob Z's illustration.
Click to expand...

On my last one I drilled and tapped the piston - the screw then got the piston moving enough to draw it out.
I think some heat was also applied to make things work easier.
Stainless pistons are available, and not very expensive. They also stop the problem from re-occurring.
 
Drilled and tapped. I'm not one of those purists who thinks everything they did at the factory is top-notch and untouchable. The other piston was a bit more corroded and pitted, so new pistons it is. Will likely use a threadlocker or teflon tape to seal the plug. JB is a bit too permanent.
 
Hi Danno, I soak my calipers in penetrant and apply 100 psi to the inlet with the bleeder in place and a spanner shank in the disc slot. I have had to heat them with a heat gun sometimes but found if I push the outer piston right back, when I apply the compressed air, the shock of the outer puck slamming into the spanner several times does get the inner puck moving. I would never drill and tap the caliper. Also, for $50, stainless pucks are well worh it. Use rubber grease on the seals during reassembly. Make sure the pucks are out as far as possible (pads against the disc and pucks against the pads) when bleeding, seems to make the process easier.

Cheers
Jeff.

My rubber grease is made by PBR (brake system specialists) it works better than the silicone grease I used the first time.
 
Didn't think of it, but didn't do the other yet anyway, but I have some Permatex Moto-Seal which is similar to Hylomar, Yamabond, Kawasakibond and other gray pliable sealants. Think I'll use that on the plug.
 
swooshdave said:
Don't drill until the last resort. Very last.

brake-caliper-teardown-yes-with-pictures-t5458.html
Click to expand...

I really couldn't figure out another way. Once the piston was drifted out of it's home, it also had to be drifted through the bore for the other one. Neither air nor grease would have helped at that point. Drilling and tapping the alloy caliper body is much easier than drilling and tapping the piston itself, which might tend to spin in place rather than let the bit cut properly.
 
I just did my 2 calipers (mkiii).

I soaked the inner Pistons in penetrating oil for a few days. Applied heat to the caliper body with a map torch and slammed the calipers on my wooden work bench a bunch of times. The Pistons worked their way out.
 
I had several stuck calipers in my collection of junk and removed all the inside pistons to find destructive corrosion on the chrome plating especially on the inner side.

I'll bet that when resurrecting a bike that has not been used for a while and maintenance to the hydraulic brakes has been neglected, the braking efficiency will be really bad due to the pistons not moving freely in/out of the caliper bores.
The seals may look OK with no leaking fluid.

Complete disassembly required.
Brake caliper overhaul questions
 
In loo of a grub screw you could use a nice stainless socket head machine screw a bit of 'Seldomseize' and a copper washer.
 
Biscuit said:
In loo of a grub screw you could use a nice stainless socket head machine screw a bit of 'Seldomseize' and a copper washer.
Click to expand...

I thought about a stainless button-head allen, but I think I'm gonna go with the stainless set screw and some Moto-Seal. KISS principle.
 
I kind of like the little plug-wart look in the middle of otherwise uninteresting caliper back side. AirCraft Spurce offers plugs in Alu but would use anti-seize like the big cap instead of sealant/glue in that case. Even if ya can clean up a rusty puck for perfect function its lost its protective chrome and will rust again even if keeping the brake fluid fresh it still always has some moisture in it. No one can predict life's hits that may leave your Cdo stored a while so SS pucks go a long ways for next fella's ease and safety. My Trixie Combat is being kept as factory un-modified as practical so when pucks did move a bit d/t her sat up rusting I took to local shop that took about 5 min to drill tap outer puck and suck right out by lifting the big in milling machine/drill press then the inner one in short order. Thinking ahead on Peel which I'd fought with pucks some years prior I had a threaded hole made on same trip as preventive medicine forethought.
 
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