Topic: Silver braze caliper piston?

[TwoTired]

what about just flipping the piston around and putting it in backwards? 

I once read a post from someone who actually did this, claiming success.  I don't think he did anything to seal the plate insert, either.  I haven't seen any posts about it since.  (I hope there isn't an unfortunate connection there.)  Anyway, I can't say I'm too enthralled with that approach.  It just seems...wrong, even if it appears to work.  For me, I think it's going to be repair the pits or replace the piston.  We'll see...

Cheers,

[csendker]

What about this stuff? --> http://www.alumaloy.net/steelaloy1.htm

It's the steel version of alumaloy.

[Dave L]

Hi
I have to say that i have had no issues with my 550 front brakes , but would like to and some of my thoughts  ,  it may not be wise to reverse
a hollowed out piston as this may cause more heat around the edge and hence affect  the seal etc .
on cars its not such a problem but on bikes it well may be !! .
I have worked on cars and found the following its not a good idea to use wd40 or any other solvent based fluid on the piston as this will cause the piston
to stick when the solvent has evaporated and in the case of my car caused a loud noise (EEEK) and this could be felt back up the hose it took some time to
work out the cause!! .
Also i have read that in the case of cars if you push back the piston without opening the bleed nipple you can damage the abs unit seals  and the ecu will then
show up a fault which can prove costly to put right , whilst this may not effect our old bikes it does make you think .
I also have found the only car Ive not had trouble with regard to corrosion on the piston was a old french 205 this had what looked like teflon coated pistons
on the front these were like new unlike the back which i think are steel or alloy these had a lot of corrosion.


I would like to say thanks for all the help Ive had with some of my problems and without the help of this site my bike may well not be running today and each
time i log on i learn a bit more

Thanks

Dave

[Clyde]

LLoyd,
I have brazed chome plated parts before using 45% silver brazing alloy and no problem.
If you are slow on the heat it does not even colour the chrome. Too much heat and you will blacken the chrome and it will not take as well as leaving the chrome yellow/blue
I have not tried brake pistons as I have not been able to clean them up enough to get the braze to take properly in the pits and I have been worried about a bit of braze falling out or jamming the piston.
If you can get them clean enough to flow the silver brazing alloy ( 45% flows very well and has a good capillary action) the I think it would be OK.
Regds Clyde

[puppytrax]

Regarding Kevins' post on phenolic brake pistons, and Lloyds' comment on SS rod made into pistons...

Why couldn't you use Nylon or even Teflon rod of the correct diameter and trim & relieve it to fit??

Lloyd is dead on with the 1.5" measurement; my CB500/550/750SS all use that diameter, with slight differences in head configuration (and the 750F has a lip). Buying medical grade Nylon or Teflon rod and cutting it to size sounds do-able to me...

[TwoTired]

Clyde,
Thanks for sharing your encouraging experiences.  I would surmise from your statements that a high spot temperature is not a good as the a wide area, heating of the braze site.  That's good to know.  Maybe the bigger torch is the way to go for the experiment.  I was thinking of using an acid etch to clean the pits before brazing for good flow and contact.  I wonder if or how it would be possible to test the bond before returning the piston to service?

 Has anybody ever removed that steel insert in piston?  Perhaps if the piston was heated from the inside, the braze might flow and adhere with more confidence?

Why couldn't you use Nylon or even Teflon rod of the correct diameter and trim & relieve it to fit??

From what I know of these materials, Nylon is too soft and would expand in the bore under compression.  The stock caliper has a nylon ring between piston and pad for just this reason, to cushion the engagement of the brakes for a few thousandths of an inch.

Teflon has cold flow characteristics that would allow it to change shape over time.  I remember working with Teflon coated cables.  And they would imprint and void when draped over metal channels in just 6 months.  We needed the Teflon for fire code applications where PVC cables were not allowed.  We had to make special installation procedures, larger bend radius specifications for Teflon cables, as well as resting support pads for places where the cables were suspended.

I like the "thinking out of the box".  It's just that sometimes things are out of the box for a reason.

Cheers,

[Jerry Rxman Griffin aka MuthaF'er]

TT,

Try a dental pick to see if the repair will pop out.

[puppytrax]

Has anybody ever removed that steel insert in piston?

Yes, I can even post a pic if you like. It's about the thickness of an elect box slug. Serves no useful purpose that I can see. One of mine popped out while I was extracting the piston from the bore. My Chevy does not use caps like these. Honda crimps them in place; but if you're taking them out, better to drill a hole & screw in a lag screw and pop it out with a claw hammer & soft-jawed vise...    

(Note: The CB750F Super Sport rear brake pistons don't use these plugs. The piston is left open.)

OK; Nylon & Teflon are out. I can get 304SS in 1.5" dia for ~$33/ft. (I don't have any). I think I'll try that.   

Better than $66 each from Honda...   

[kslrr]

The steel plug might be there to dampen vibration and squeal by adding some mass to the piston.